The child outcomes described above provide the context for considering the range of parenting knowledge, attitudes, and practices and identifying those that research supports as core. As noted in Chapter 1, the term “knowledge” for the purposes of this report refers to facts, information, and skills gained through experience or education and understanding of an issue or phenomenon. “Attitudes” refers to viewpoints, perspectives, reactions, or settled ways of thinking about aspects of parenting or child development, including parents' roles and responsibilities. Attitudes may be related to cultural beliefs founded in common experience. And “practices” refers to parenting behaviors or approaches to childrearing that can shape how a child develops. Generally speaking, knowledge relates to cognition, attitudes relate to motivation, and practices relate to ways of engaging or behavior, but all three may emanate from a common source.
These three components are reciprocal and intertwined theoretically, empirically, and bidirectionally, informing one another. For example, practices are related to knowledge and attitudes, and often involve the application of knowledge. According to behavior modification theory (Ajzen and Fishbein, 1980; Fishbein et al., 2001), a person's attitude often determines whether he or she will use knowledge and transform it into practice. In short, if one does not believe in or value knowledge, one is less likely to act upon it. What parents learn through the practice of parenting can also be a source of knowledge and can shape parents' attitudes. Parenting attitudes are influenced as well by parenting self-efficacy, which has been broadly defined as the level of parents' self-belief about their ability to succeed in the parenting role (Jones and Prinz, 2005).
Parenting knowledge, attitudes, and practices are shaped not only by each other but also by a number of contextual factors, including children's characteristics (e.g., gender, temperament); parents' own experiences (e.g., those from their own childhood) and circumstances; expectations learned from others, such as family, friends, and other social networks; and cultural systems. Of particular relevance to this study, the contextual factors that influence parenting knowledge, attitudes, and practices also include the supports available within the larger community and provided by institutions, as well as by policies that affect the nature and availability of supportive services.
In response to the study charge (Box 1-2 in Chapter 1), this chapter presents the evidence on core parenting knowledge, attitudes, and practices separately. However, it should be noted that in the research literature, the distinctions among these concepts, especially knowledge and attitudes, are not well-delineated and that the applications of these concepts to parenting often are equally informed by professional wisdom and historical observation.
Parenting is multidimensional. To respond to the varied needs of their children, parents must develop both depth and breadth of knowledge, ranging from being aware of developmental milestones and norms that help in keeping children safe and healthy to understanding the role of professionals (e.g., educators, child care workers, health care providers, social workers) and social systems (e.g., institutions, laws, policies) that interact with families and support parenting. This section describes these areas of knowledge, as well as others, identified by the available empirical evidence as supporting core parenting practices and child outcomes. It is worth noting that the research base regarding the association between parental knowledge and child outcomes is much smaller than that on parenting practices and child outcomes (Winter et al., 2012). Where data exist, they are based largely on correlational rather than experimental studies.
Knowledge of Child Development
[Some parents recognized the need for education related to providing care for young children.]
“I am a new parent and even though I have a bachelor's degree from India, I do not have a particular education in child care. Just because I have a degree, it does not mean it is a degree on how to take care of a child.”
—Father from Omaha, Nebraska
The importance of parents' knowledge of child development is a primary theme of many efforts to support parenting. Evidence-based recommendations issued by the American Psychological Association Task Force on Evidence-Based Practice with Children and Adolescents (2008), the Centers for Disease Control and Prevention (CDC) (2015b), and the World Health Organization (WHO) (2009) emphasize the need for policy and program initiatives to promote parenting knowledge. As they suggest, to optimize children's development, parents need a basic understanding of infant and child developmental milestones and norms and the types of parenting practices that promote children's achievement of these milestones (Belcher et al., 2007; Benasich and Brooks-Gunn, 1996, p. 1187; Bond and Burns, 2006; Bornstein and Cote, 2004; Hess et al., 2004; Huang et al., 2005; Larsen and Juhasz, 1985; Mercy and Saul, 2009).
A robust body of correlational research demonstrates tremendous variation in parents' knowledge about childrearing. Several of these studies suggest that parents with higher levels of education tend to know more about child developmental milestones and processes (Bornstein et al., 2010; Conrad et al., 1992; Hess et al., 2004; Huang et al., 2005), as well as effective parenting strategies (Morawska et al., 2009). This greater knowledge may reflect differential access to accurate information, differences in parents' trust in the information or information source, and parents' comfort with their own abilities, among other factors. For example, research shows that parents who do not teach math in the home tend to have less knowledge about elementary math, doubt their competence, or value math less than other skills (Blevins-Knabe et al., 2000; Cannon and Ginsburg, 2008; Vukovic and Lesaux, 2013). However, parents' knowledge and willingness to increase their knowledge may change; thus, they can acquire developmental knowledge that can help them employ effective parenting practices.
[Some parents recognized the need for comprehensive parenting education.]
“I always prefer education for the parents, from the beginning to the end. From pregnancy, some don't know when to go to the doctor, and after birth, when to go to the hospital or the doctor. So we need education from the beginning to the end.”
—Mother from Omaha, Nebraska
The focus on parental knowledge as a point of intervention is important because parents' knowledge of child development is related to their practices and behaviors (Okagaki and Bingham, 2005). For example, mothers who have a strong body of knowledge of child development have been found to interact with their children more positively compared with mothers with less knowledge (Bornstein and Bradley, 2012; Huang et al., 2005). Parents who understand child development also are less likely to have age-inappropriate expectations for their child, which affects the use of appropriate discipline and the nature and quality of parent-child interactions (Goodnow, 1988; Huang et al., 2005).
Support for the importance of parenting knowledge to parenting practices is found in multiple sources and is applicable to a range of cognitive and social-emotional behaviors and practices. Several correlational studies show that mothers with high knowledge of child development are more likely to provide books and learning materials tailored to children's interests and age and engage in more reading, talking, and storytelling relative to mothers with less knowledge (Curenton and Justice, 2004; Gardner-Neblett et al., 2012; Grusec, 2011). Fathers' understanding of their young children's development in language and literacy is associated with being better prepared to support their children (Cabrera et al., 2014). And parents who do not know that learning begins at birth are less likely to engage in practices that promote learning during infancy (e.g., reading to infants) or appreciate the importance of exposing infants and young children to hearing words and using language. For example, mothers who assume that very young children are not attentive have been found to be less likely to respond to their children's attempts to engage and interact with them (Putnam et al., 2002).
Stronger evidence of the role of knowledge of child development in supporting parenting outcomes comes from intervention research. Randomized controlled trial interventions have found that parents of young children showed increases in knowledge about children's development and practices pertaining to early childhood care and feeding (Alkon et al., 2014; Yousafzai et al., 2015).
Some studies have found a direct association between parental knowledge and child outcomes, including reduced behavioral challenges and improvements on measures of cognitive and motor performance (Benasich and Brooks-Gunn, 1996; Dichtelmiller et al., 1992; Hunt and Paraskevopoulos, 1980; Rowe et al., 2015). In an analysis of data from a prospective cohort study that controlled for potential confounders, children of mothers with greater knowledge of child development at 12 months were less likely to have behavior problems and scored higher on child IQ tests at 36 months relative to children of mothers with less developmental knowledge (Benasich and Brooks-Gunn, 1996). This and other observational studies also show that parental knowledge is associated with improved parenting and quality of the home environment, which, in turn, is associated with children's outcomes (Benasich and Brooks-Gunn, 1996; Parks and Smeriglio, 1986; Winter et al., 2012), in addition to being contingent on parental attitudes and competence (Conrad et al., 1992; Hess et al., 2004; Murphy et al., 2015).
Experimental studies of parent education interventions support these associational findings. In an experimental study of parent education for first-time fathers, fathers, along with home visitors, reviewed examples of parental sensitivity and responsiveness from videos of themselves playing with their children (Magill-Evans et al., 2007). These fathers showed a significant increase in parenting competence and skills in fostering their children's cognitive growth as well as sensitivity to infant cues 2 months after the program, compared with fathers in the control group, who discussed age-appropriate toys with the home visitor (Magill-Evans et al., 2007). Another experimental study examined a 13-week population-level behavioral parenting program and found intervention effects on parenting knowledge for mothers and, among the highest-risk families, increased involvement in children's early learning and improved behavior management practices. Lower rates of conduct problems for boys at high risk of problem behavior also were found (Dawson-McClure et al., 2015).
Knowledge of Parenting Practices
Parents' knowledge of how to meet their children's basic physical (e.g., hunger) and emotional (e.g., wanting to be held or soothed) needs, as well as of how to read infants' cues and signals, can improve the synchronicity between parent and child, ensuring proper child growth and development. Specifically, parenting knowledge about proper nutrition, safe sleep environments, how to sooth a crying baby, and how to show love and affection is critical for young children's optimal development (Bowlby, 2008; Chung-Park, 2012; Regalado and Halfon, 2001; Zarnowiecki et al., 2011).
For many parents, for example, infant crying is a great challenge during the first months of life. Parents who cannot calm their crying babies suffer from sleep deprivation, have self-doubt, may stop breastfeeding earlier, and may experience more conflict and discord with their partners and children (Boukydis and Lester, 1985; Karp, 2008). Correlational research indicates that improvement in parental knowledge about normal infant crying is associated with reductions in unnecessary medical emergency room visits for infants (Barr et al., 2015). That knowledge leads to changes in behavior is further supported in systematic reviews by Bryanton and colleagues (2013) of randomized controlled trials and Middlemiss and colleagues (2015) of studies with various design types, with both groups reporting that increases in mother's knowledge about infant behavior is associated with positive changes in the home environment, as well as improvements in infant sleep time.
Specific knowledge about health and safety—including knowledge about how to access health care, protect children from physical harm (e.g., the importance of wearing a seat belt or a helmet), and promote good hygiene and nutrition—is a key parenting competency. Experimental studies show, for example, a positive link between parents' knowledge of nutrition and both children's intake of nutritious foods and reduced calorie and sodium intake (Campbell et al., 2013; Katz et al., 2011). In a randomized controlled trial, Campbell and colleagues (2013) found that children whose parents received knowledge, skills, and social support related to infant feeding, diet, physical activity, and television viewing consumed fewer sweet snacks and spent fewer minutes daily viewing television relative to children whose parents were in the control group (Campbell et al., 2013). Also associated with children's intake of nutritious foods is parents' modeling of good eating habits and nutritional practices (Mazarello Paes et al., 2015).
In addition, although limited in scope, correlational evidence shows that parents with knowledge about immunization are more likely to understand its purpose and comply with the timetable for vaccinations (Smailbegovic et al., 2003); that parents with more knowledge about effective injury prevention practices are more likely to create safer home environments for their children and reduce unintentional injuries (Corrarino, 2013; Dowswell et al., 1996; Middlemiss et al., 2015; Morrongiello and Kiriakou, 2004); and that parents with knowledge about asthma are more likely to use an asthma management plan (Bryant-Stephens and Li, 2004; DeWalt et al., 2007; Harrington et al., 2015). Other studies have found that parents with more information about the purpose of vaccinations had greater knowledge of immunization than parents in the control group (Hofstetter et al., 2015; Jackson et al., 2011), and parents with more knowledge about sun safety provided sunscreen and protective clothing for their children, who presented with fewer sunburns (Crane et al., 2012).
Still, knowledge alone may not be sufficient in some cases. For example, knowing about the importance of using car seats does not always translate into good car seat practices (Yanchar et al., 2012, 2015), and knowledge about the advantages of vaccines may not result in parents choosing to vaccinate their children. Some findings suggest that using multiple modes of delivery is important to advancing parents' knowledge. In an experimental study, for example, Dunn and colleagues (1998) found that parents who received educational information about child vaccinations via videotape as well as in written form showed greater gains in understanding about vaccinations than parents who received the information in written form alone.
The evidence linking parental knowledge about the specific ways in which parents can help children develop cognitive and academic skills, including skills in math, is limited. However, the available correlational data show that parents who know about how children develop language are more likely to have children with emergent literacy skills (e.g., letter sound awareness) relative to parents who do not (Ladd et al., 2011). Several studies over the past 20 years have described parents' increasing knowledge and use of approaches for supporting children's literacy (Clark, 2007; National Research Council, 1998; Sénéchal and LeFevre, 2002). Much of this work has focused on book reading and parent-child engagement around reading (Hindman et al., 2008; Mol et al., 2008; Morrow et al., 1990). As early as the 1960s, Durkin (1966) and others referred to the important role of the home literacy environment and parents' beliefs about reading in children's early literacy development.
Knowledge of Supports, Services, and Systems
Little is known about parents' knowledge of various supports—such as educators, social workers, health care providers, and extended family—and the relationship between their conceptions of the roles of these supports and their use of them.
To take an example, parents' knowledge about child care and their school decision-making processes are informed in a variety of ways through these different supports. In their literature review of child care decision making, Forry and colleagues (2013) found that many low-income parents learn about their child care options through their social networks rather than through professionals or referral agencies. While many parents say they highly value quality, their choices also may reflect a range of other factors that are valued. Parents tend to make child care decisions based on structural (teacher education and training) and process (activities, parent-provider communication) features, although their choices also vary by family income, education, and work schedules. Sosinsky and Kim (2013), for example, found that higher maternal education and income and being white were associated with the likelihood of parents choosing higher-quality child care programs that were associated with better child outcomes. Based on a survey of parents of children in a large public school system, Goldring and Phillips (2008) found that parents' involvement, not satisfaction with their child's school, was associated with school decision making. It should be noted that while parents may know what constitutes high-quality child care and education, structural (availability of quality programs and schools), individual (work, income, belief), and child (temperament, age) factors also influence these decision-making processes (Meyers and Jordan, 2006; Shlay, 2010).
Taking another example, limited studies have looked at parental awareness of services for children with special needs. A study that utilized a survey and qualitative interviews with parents of children with autism indicated that parents' autism spectrum disorder service knowledge partially mediates the relationship between socioeconomic status and use of services for their children (Pickard and Ingersoll, 2015).
Although considerable discussion has focused on attitudes and beliefs broadly, less research attention has been paid to the effects of parenting attitudes on parents' interactions with young children or on parenting practices. Few causal analyses are available to test whether parenting attitudes actually affect parenting practices, positive parent-child interaction, and child development. Even less research exists on fathers' attitudes about parenting. Given this limited evidence base, the committee drew primarily on correlational and qualitative studies in examining parenting attitudes.
Parents' attitudes toward parenting are a product of their knowledge of parenting and the values and goals (or expectations) they have for their children's development, which in turn are informed by cultural, social, and societal images, as well as parents' experiences and their overall values and goals (Cabrera et al., 2000; Cheah and Chirkov, 2008; Iruka et al., 2015; Okagaki and Bingham, 2005; Rogoff, 2003; Rosenthal and Roer-Strier, 2006; Whiting and Whiting, 1975). People in the United States hold several universal, or near universal, beliefs about the types of parental behaviors that promote or impair child development. For example, there is general agreement that striking a child in a manner that can cause severe injury, engaging in sexual activity with a child, and failing to provide adequate food for and supervision of young children (such as leaving toddlers unattended) pose threats to children's health and safety and are unacceptable. At the same time, some studies identify differences in parents' goals for child development, which may influence attitudes regarding the roles of parents and have implications for efforts to promote particular parenting practices.
While there is variability within demographic groups in parenting attitudes and practices, some research shows differences in attitudes and practices among subpopulations. For example, qualitative research provides some evidence of variation by culture in parents' goals for their children's socialization. In one interview study, mothers who were first-generation immigrants to the United States from Central America emphasized long-term socialization goals related to proper demeanor for their children, while European American mothers emphasized self-maximization (Leyendecker et al., 2002). In another interview study, Anglo American mothers stressed the importance of their young children developing a balance between autonomy and relatedness, whereas Puerto Rican mothers focused on appropriate levels of relatedness, including courtesy and respectful attentiveness (Harwood et al., 1997). Other ethnographic and qualitative research shows that parents from different cultural groups select cultural values and norms from their country of origin as well as from their host country, and that their goal is for their children to adapt and succeed in the United States (Rogoff, 2003).
Similarly, whereas the larger U.S. society has historically viewed individual freedom as an important value, some communities place more emphasis on interdependence (Elmore and Gaylord-Harden, 2013; Sarche and Spicer, 2008). The importance of intergenerational connections (e.g., extended family members serving as primary caregivers for young children) also varies among and within cultural communities (Bertera and Crewe, 2013; Mutchler et al., 2007). The values and traditions of cultural communities may be expressed as differences in parents' views regarding gender roles, in parents' goals for children, and in their attitudes related to childrearing.
[One parent described differences between men and women in parenting roles.]
“Mothers play the main role as parents in [certain cultures]. Culturally men aren't that involved. The dad is the outer worker; the mother is the inner worker. If you are talking about the mom, they are the ones who care about the kids. They aren't typically working outside the home. But now, in the United States, the mothers are working outside the home.”
—Father from Omaha, Nebraska
Although slowly changing, attitudes about the roles of men and women in the raising of young children often differ between men and women and among various communities in the United States. Longitudinal research on mothers' attitudes toward fathers' involvement in childrearing has made reference to the “gatekeeping” role of mothers of children with nonresidential fathers (Fagan and Barnett, 2003; Schoppe-Sullivan et al., 2008). Research has shown that fathers of young children participate in child caregiving activities in increasing numbers (Cabrera et al., 2011), but has not examined the specific attitudes that fathers bring to particular parenting behaviors across the life span. Parents' values and goals related to childrearing, both overall and for specific demographic groups, also may shift from one generation to the next in the United States based on changing norms and viewpoints within social networks and cultural communities, as well as parents' knowledge of and access to new research and information provided by educators, health care providers, and others who work with families.
Relatively little research has been conducted on parents' attitudes toward specific parenting-related practices. Much of the extant research focuses on practices related to promoting children's physical health and safety. Studies of varying designs indicate that parental attitudes and beliefs about the need for and safety of vaccination influence vaccination practices (Mergler et al., 2013; Salathé and Bonhoeffer, 2008; Vannice et al., 2011; Yaqub et al., 2014). Maternal attitudes and beliefs about breastfeeding (e.g., views about breastfeeding in public, the belief that it will be uncomfortable) are associated with initiation and continuation of breastfeeding and appear to factor into differences in breastfeeding rates and practices observed across cultural and other demographic groups in cross-sectional survey and qualitative research (Vaaler et al., 2010; Wojcicki et al., 2010). Other studies have found differences among parents (e.g., those living in rural versus urban areas) in attitudes about the importance of monitoring children's activities and whereabouts (Armistead et al., 2002; Jones et al., 2003) and parents' beliefs about young children's literacy development (Lynch et al., 2006).
Parental involvement in children's education has been linked to academic readiness (Fan and Chen, 2001). However, parents differ in their attitudes about the role of parents in children's learning and education (Hammer et al., 2007). Some see parents as having a central role, while others view the school as the primary facilitator of children's education and see parents as having less of a role (Hammer et al., 2007). These attitudinal differences may be related to cultural expectations or parents' own education or comfort with teaching their children certain skills. Some parents, for example, may have lower involvement in their children's education because of insecurity about their own skills and past negative experiences in school (Lareau, 1989; Lawrence-Lightfoot, 2003). And as discussed above, some parents view math skills as less important for their children relative to other types of skills and therefore are less likely to teach them in the home.
Parents within and across different communities vary in their opinions and practices with respect to the role and significance of discipline. Some of the parenting literature notes that some parents use control to discipline children, while others aim to correct but not to control children (Nieman and Shea, 2004). In a small cross-cultural ethnographic study, Mosier and Rogoff (2003) found that some parents regard rules and punishment as inappropriate for infants and toddlers. The approach valued by these parents to help children understand what is expected of them is to cooperate with them, perhaps distracting them but not forcing their compliance. In contrast, many middle-class U.S. parents display a preference for applying the same rules to infants and toddlers that older children are expected to follow, although with some lenience (Mosier and Rogoff, 2003). And ethnographic research provides some evidence of differences in African American and European American mothers' beliefs about spoiling and infant intentionality (whether infants can intentionally misbehave) related to the use of physical punishment with young children (Burchinal et al., 2010).
Parents' attitudes not only toward parenting but also toward providers in societal agencies—such as educators, social service personnel, health care providers, and police—which can be shaped by a variety of factors, including discrimination, are important determinants of parents' access to and ability to obtain support. Studies show a relationship between parents' distrust of agencies and their likelihood of rejecting participation in an intervention. For example, in systematic reviews of studies of various types, parents who distrust the medical community and government health agencies are less likely to have their children vaccinated (Brown et al., 2010; Mills et al., 2005). Racial and ethnic minority parents whose attitudes about appropriate remedies for young children vary from those of the Western medical establishment often distrust and avoid treatment by Western medical practitioners (Hannan, 2015). While not specific to parents, studies using various methodologies show that individuals who have experienced racial and other forms of discrimination, both within and outside of health care settings, are less likely to utilize various health services or to engage in other health-promoting behaviors (Gonzales et al., 2013; Institute of Medicine, 2003; Pascoe and Smart Richman, 2009; Shavers et al., 2012). In a survey study, African American parents' racism awareness was negatively associated with involvement in activities at their children's school (McKay et al., 2003). Longitudinal studies, mostly involving families with older children, indicate that, like other sources of stress, parents' experience of discrimination can have a detrimental effect on parenting and the quality of the parent-child relationship (Murray et al., 2001; Sanders-Phillips et al., 2009). Adverse outcomes for youth associated with their own experience of discrimination may be weakened by more nurturing/involved parenting (Brody et al., 2006; Gibbons et al., 2010; Simons et al., 2006).
As noted earlier, attitudes are shaped in part by parenting self-efficacy—a parent's perceived ability to influence the development of his or her child. Parenting self-efficacy has been found to influence parenting competence (including engagement in some parenting practices) as well as child functioning (Jones and Prinz, 2005). Studies show associations between maternal self-efficacy and children's self-regulation, social, and cognitive skills (Murry and Brody, 1999; Swick and Hassell, 1990). Self-efficacy also may apply to parents' confidence in their capacity to carry out specific parenting practices. For example, parents who reported a sense of efficacy in influencing their elementary school-age children's school outcomes were more likely to help their children with school activities at home (Anderson and Minke, 2007). A multimethod study of African American families found that maternal self-efficacy was related to children's regulatory skills through its association with competence-promoting parenting practices, which included family routines, quality of mother-child interactions based on observer ratings, and teachers' reports of mothers' involvement with their children's schools (Brody et al., 1999). Henshaw and colleagues (2015) found in a longitudinal study that higher breastfeeding self-efficacy predicted exclusive breastfeeding at 6 months postpartum, as well as better emotional adjustment of mothers in the weeks after giving birth.
Parenting practices have been studied extensively, with some research showing strong associations between certain practices and positive child outcomes. This section describes parenting practices that research indicates are central to helping children achieve basic outcomes in the areas discussed at the beginning of the chapter: physical health and safety, emotional and behavioral competence, social competence, and cognitive competence. While these outcomes are used as a partial organizing framework for this section, several specific practices—contingent responsiveness of parents, organization of the home environment and the importance of routines, and behavioral discipline practices—that have been found to influence child well-being in more than one of these four outcome areas are discussed separately.
Practices to Promote Physical Health and Safety
Parents influence the health and safety of their children in many ways. However, the difficulty of using random assignment designs to examine parenting practices that promote children's health and safety has resulted in a largely observational literature. This section reviews the available evidence on a range of practices in which parents engage to ensure the health and safety of their children. It begins with breastfeeding—a subject about which there has historically been considerable discussion in light of generational shifts and commercial practices that have affected children in poor families.
Breastfeeding Breastfeeding has myriad well-established short- and long-term benefits for both babies and mothers. Breast milk bolsters babies' immunity to infectious disease, regulates healthy bacteria in the intestines, and overall is the best source of nutrients to help babies grow and develop. Breastfeeding also supports bonding between mothers and their babies. According to a meta-analysis by the WHO (Horta and Victora, 2013), breastfeeding is associated with a small increase in performance on intelligence tests in children and adolescents, reduced risk for the development of type 2 diabetes and overweight/obesity later in life, and a potential decreased risk for the development of cardiovascular disease. Breastfeeding may benefit mothers' health as well by lowering risk for postpartum depression, certain cancers, and chronic diseases such as diabetes (U.S. Department of Health and Human Services, 2011). Current guidelines from the American Academy of Pediatrics (2012) and the WHO (2011) recommend mothers breastfeed exclusively until infants are 6 months old. Thereafter and until the child is either age 1 year (American Academy of Pediatrics, 2012) or 2 years (World Health Organization, 2011), it is recommended that children continue to be breastfed while slowly being introduced to other foods.
According to 2011 data from the CDC (2015a), about 80 percent of babies born in the United States are breastfed (including fed breast milk) for some duration, and about 50 percent and 27 percent are breastfed (to any extent with or without the addition of complementary liquids or solids) at 6 and 12 months, respectively. Forty percent and 19 percent are exclusively breastfed through 3 and 6 months, respectively.
Mothers in the United States often cite a number of reasons for not initiating or continuing breastfeeding, including lack of knowledge about how to breastfeed, difficulty or pain during breastfeeding, embarrassment, perceived inconvenience, and return to work (Hurley et al., 2008; Ogbuanu et al., 2009; U.S. Department of Health and Human Services, 2011). Low-income women with less education are less likely than women of higher socioeconomic status to breastfeed (Heck et al., 2006). Some research with immigrant mothers shows that rates of breastfeeding decrease with each generation in the United States, possibly because of differences in acceptance of bottle feeding here as compared with other countries (e.g., Sussner et al., 2008).
Nutrition and physical activity Parents play an important role in shaping their young children's nutrition and physical activity levels (Institute of Medicine, 2011; Sussner et al., 2006). Among toddlers and preschool-age children, parents' feeding practices are associated with their children's ability to regulate food intake, which can affect weight status (Faith et al., 2004; Farrow et al., 2015). Parents' modeling of healthful eating habits for their children and offering of healthful foods, particularly during toddlerhood, when children are often reluctant to try new foods, may result in children being more apt to like and eat such foods (Hill, 2002; Natale et al., 2014; Sussner et al., 2006). The extant observational research generally shows that children's dietary intake (particularly fruit and vegetable consumption) is associated with food options available in the home and at school, and that parents are important role models for their children's dietary behaviors (Cullen et al., 2003; Pearson et al., 2009; Wolnicka et al., 2015). Conversely, the presence of less nutritious food and beverage items in the home may increase children's risk of becoming overweight. For example, Dennison and colleagues (1997) and Welsh and colleagues (2005) found positive associations between overweight in children and their consumption of sugar-sweetened beverages. On the other hand, there are some indications that overly strict diets may increase children's preferences for high-fat, energy-dense foods, perhaps causing an imbalance in children's self-regulation of hunger and satiety and increasing the risk that they will become overweight (Birch and Fisher, 1998; Farrow et al., 2015).
A few cross-sectional and longitudinal studies, coupled with conventional wisdom, suggest that eating dinner together as a family is associated with increased consumption of fruits, vegetables, and whole grains and reduced consumption of fats and soda (Gillman et al., 2000), as well as with reduced risk for overweight and obesity (Gable et al., 2007; Taveras et al., 2005). However, these studies involved primarily older children and adolescents.
Physical activity is a complement to good nutrition. Even in young children, physical activity is essential for proper energy balance and prevention of childhood obesity (Institute of Medicine, 2011; Kohl and Hobbs, 1998). It also supports normal physical growth. Parents may encourage activity in young children through play (e.g., free play with toys or playing on a playground) or age-appropriate sports. Children who spend more time outdoors may be more active (e.g., Institute of Medicine, 2011; Sallis et al., 1993) and also have more opportunity to explore their community and interact with other children. For many parents living in high-crime neighborhoods, however, most of whom are racial and ethnic minorities, the importance of safety overrides the significance of physical activity. In some neighborhoods, safety issues and lack of access to parks and other places for safe recreation make it difficult for families to spend time outdoors, leading parents to keep their children at home (Dias and Whitaker, 2013; Gable et al., 2007; Powell et al., 2003).
Although more of the research on screen time and sedentary behavior has focused on adolescents than on young children, several cross-sectional and longitudinal studies on younger children show an association between television viewing and overweight and inactivity (Ariza et al., 2004; Carson et al., 2016; Dennison et al., 2002; DuRant et al., 1994; Gable et al., 2007; Tremblay et al., 2011). An analysis of data on 8,000 children participating in a longitudinal cohort study showed that those who watched more television during kindergarten and first grade were significantly more likely to be clinically overweight by the spring semester of third grade (Gable et al., 2007). Although television, computers, and other screen media often are used for educational purposes with young children, these findings suggest that balancing screen time with other activities may be one way parents can promote their children's overall health. As with diet, children's sedentary behavior can be influenced by parents' own behaviors. For example, De Lepeleere and colleagues (2015) found an association between parents' screen time and that of their children ages 6-12 in a cross-sectional study.
Vaccination Parents protect their own and other children from potentially serious diseases by making sure they receive recommended vaccines. Among children born in a given year in the United States, childhood vaccination is estimated to prevent about 42,000 deaths and 20 million cases of disease (Zhou et al., 2014). In 2013, 82 percent of children ages 19-35 months received combined-series vaccines (for diphtheria, tetanus, and pertussis [DTP]; polio; measles, mumps, and rubella [MMR]; and Haemophilus influenzae type b [Hib]), up from 69 percent in 1994 (Child Trends Databank, 2015b). Vaccination rates are lower among low-income children; 71 percent of children ages 19-35 months living below the poverty level received the combined-series vaccines listed above in 2014 (Child Trends Databank, 2015b). Although much of the media coverage on this subject has focused on middle-income parents averse to having their children vaccinated, it is in fact poverty that is thought to account for much of the disparity in vaccination rates by race and ethnicity (Hill et al., 2015). As discussed earlier in this chapter, parental practices around vaccination may be influenced by parents' knowledge and interpretation of information on and their attitudes about vaccination.
Preconception and prenatal care The steps women take with their health care providers before becoming pregnant can promote healthy pregnancy and birth outcomes for both mothers and babies. These include initiating certain supplements (e.g., folic acid, which reduces the risk of birth defects), quitting smoking, attaining healthy weight for women who are obese, and treating preexisting physical and mental health conditions (Aune et al., 2014; Gold and Marcus, 2008; Institute of Medicine and National Research Council, 2009).
During pregnancy, receipt of recommended prenatal care can help parents reduce the risk of pregnancy complications and poor birth outcomes by promoting healthy behaviors (e.g., smoking cessation, adequate rest and nutrition), as well as identifying and managing any complications that do arise. Prior to the birth of a child, health care providers also can educate parents on the importance of breastfeeding, infant injury and illness prevention, and other practices.
Infants born to mothers who do not receive prenatal care or who do not receive it until late in their pregnancy are more likely than those born to mothers who receive such care early in pregnancy to be born premature and at a low birth weight and are more likely to die. Since the 1970s, there has been a decline in the number of women in the United States receiving late or no prenatal care, with the majority of pregnant women now receiving recommended prenatal care (Child Trends Databank, 2015a). Yet disparities among subgroups persist. In 2014, American Indian and Alaska Native (11% of births), black (10% of births), and Hispanic (8% of births) women were more than twice as likely as white mothers (4% of births) to receive late or no prenatal care (Child Trends Databank, 2015a). The proportion of women receiving timely prenatal care increases with age: in 2014, 25 percent of births to females under age 15 and 10 percent of births to females ages 15-19 were to mothers receiving late or no prenatal care, compared with 7.8 percent for females ages 20-24 and 5.6 percent for those ages 25-29 (Child Trends Databank, 2015a). Women whose pregnancies are unintended also are less likely to receive timely prenatal care. Despite the importance of timely and quality prenatal care, moreover, many parents experience barriers to receiving such care, including poor access and rural residence, limited knowledge of its importance, and mental illness (Heaman et al., 2014).
Injury prevention Unintentional injuries are the leading cause of death among children ages 1-9 (Centers for Disease Control and Prevention, 2015c) and a leading cause of disability for both younger and older children in the United States. In addition to motor vehicle-related injuries, children sustain unintentional injuries (due, for example, to suffocation, falls, poisoning, and drowning) in the home environment. About 1,700 children under age 9 in the United States die each year from injuries in the home (Mack et al., 2013).
Parents can protect their children from injury through various measures, such as ensuring proper use of automobile passenger restraints, insisting that children wear helmets while bike riding and playing sports, and creating a safe home environment (e.g., keeping medicines and cleaning products out of children's reach, installing safety gates to keep children from falling down stairs). Yet the limited available research on parents' use of safety measures suggests there is room for improvement in some areas. For instance, appropriate use of child restraint systems is known to reduce the risk of child motor vehicle-related injuries and deaths (Arbogast et al., 2009; Durbin, 2011); nonetheless, data show that many children ride in automobiles without appropriate restraints (Greenspan et al., 2010; Lee et al., 2015; Macy et al., 2014). Likewise, using data from a national survey conducted during 2001-2003, Dellinger and Kresnow (2010) show that less than one-half of children ages 5-14 always wore bicycle helmets while riding, and 29 percent never did so. More recent data on parents' home safety practices and on helmet usage among young children are lacking.
Evidence that families' home safety practices affect child safety comes from intervention research. A large meta-analysis of randomized and nonrandomized controlled trials of home safety education interventions for families (Kendrick et al., 2013) showed that the education was generally effective in increasing the proportion of families that stored medicines and cleaning products out of reach and that had fitted stair gates, covers on unused electrical sockets, safe hot tap water temperatures, functional smoke alarms, and a fire escape system. There was also some evidence for reduced injury rates among children. As discussed in Chapter 4, helping parents reduce hazards in the home is a component of some home visiting programs.
Parents also protect their children's safety by monitoring their whereabouts and activities to prevent them from both physical and psychological harm. The type of supervision may vary based on a child's needs and age as well as parents' values and economic circumstances. For all young children, monitoring for the purposes of preventing exposure to hazards is an important practice. As children grow older, knowing their friends and where the children are when they are not at home or in school also becomes important. As noted previously, research suggests the importance of monitoring screen time to children's well-being. And monitoring of children's Internet usage may prevent them from being exposed to online predators (Finkelhor et al., 2000).
Practices to Promote Emotional and Behavioral Competence and Social Competence
Fundamental to children's positive development is the opportunity to grow up in an environment that responds to their emotional needs (Bretherton, 1985) and that enables them to develop skills needed to cope with basic anxieties, fears, and environmental challenges. Parents' ability to foster a sense of belonging and self-worth in their children is vital to the children's early development. In much the same way, parents contribute to children's emerging social competence by teaching them skills—such as self-control, cooperation, and taking the perspective of others—that prepare them to develop and maintain positive relationships with peers and adults. Parents can promote the learning and acquisition of social skills by establishing strong relationships with their children. The importance of early parent-child interactions for children's social competence is embedded in many theoretical frameworks, such as attachment (Ainsworth and Bowlby, 1991), family system theories (Cox and Paley, 1997), and ecocultural theories (Weisner, 2002). Parents socialize their children to adopt culturally appropriate values and behaviors that enable them to be socially competent and act as members of a social group.
Research suggests that children who are socially competent are independent rather than suggestible, responsible rather than irresponsible, cooperative instead of resistive, purposeful rather than aimless, friendly rather than hostile, and self-controlled rather than impulsive (Landy and Osofsky, 2009). In short, the socially competent child exhibits social skills (e.g., has positive interactions with others, expresses emotions effectively), is able to establish peer relationships (e.g., being accepted by other children), and has certain individual attributes (e.g., shows capacity to empathize, has coping skills). Parents help children develop these social skills through parenting practices that include fostering and modeling positive relationships and providing enriching and stimulating experiences and opportunities for children to exercise these skills (Landy and Osofsky, 2009). Parents also help their children acquire these skills by having them participate in routine activities (e.g., chores, taking care of siblings) and family rituals (e.g., going to church) (Weisner, 2002). These activities are shared with and initiated by parents, siblings, and other kin; unfold within the home; and are structured by cultural and linguistic practices, expectations, and behaviors (Rogoff, 2003; Weisner, 2002). In this context, young children interact with their mothers, fathers, siblings, and grandparents who teach them implicitly or explicitly to acquire appropriate social behaviors, adapt to expected norms, and learn linguistic conventions and cognitive skills (Sameroff and Fiese, 2000).
Another important aspect of parent-supported social development pertains to parents aiding their children in acquiring executive function skills needed to adapt to changing needs of the environment and regulate their impulses and responses to distressing situations (Blair and Raver, 2012; Malin et al., 2014; Thompson, 1994). Evidence, primarily from correlational research, suggests that parents who help their children regulate the difficulty of tasks and who model mature performance during joint participation in activities are likely to have socially competent children (Eisenberg et al., 1998). Parents also facilitate their children's development of friendships by engaging in positive social interaction with them and by creating opportunities for them to be social with peers (McCollum and Ostrosky, 2008). In one correlational study, children whose parents initiated peer contacts had more playmates and more consistent play companions in their preschool peer networks (Ladd et al., 2002). Research also shows that children who have increased opportunities for playing or interacting with children from diverse backgrounds are likely to develop less prejudice and more empathy toward others (Bernstein et al., 2000; Perkins and Mebert, 2005; Pettigrew and Tropp, 2000).
Findings from experimental studies on parent training provide evidence of the types of parental practices that are associated with child emotional and behavioral health (i.e., fewer internalizing and externalizing problems) and social competence (i.e., relationship building skills, moral dispositions, and prosocial behaviors such as altruism). In one study for example, parent training designed to decrease the use of harsh discipline and increase supportive parenting reduced mother-reported child behavior problems in children ages 3-9 (Bjørknes and Manger, 2013). In another randomized study, mothers who received parent training to improve their empathy toward their children became less permissive with their 2- to 3-year-olds, who became less aggressive (Christopher et al., 2013).
These relationships have been found to hold in experimental studies involving diverse samples. Brotman and colleagues (2005) found that a program designed to reduce parents' use of negative parenting and increase their provision of stimulation for child learning increased social competence with peers in young African American and Latino children who had a sibling who had been involved in the juvenile justice system. In a European study, Berkovits and colleagues (2010) studied ethnically diverse parents participating in an abbreviated parent skills training delivered in pediatric primary care aimed at encouraging children's prosocial behavior. The findings show significant increases in effective parenting strategies and in parents' beliefs about personal controls, as well as declines in child behavior problems. Improvements in child behavior as a consequence of parent training have been found not only for programs emphasizing better and more consistent discipline and contingency management, but also for those providing training that led to parents' greater emotional support for their children (McCarty et al., 2005). In addition, Stormshak and colleagues (2000) found that punitive interactions between parents and children were associated with higher rates of child disruptive behavior problems, and that low levels of warm involvement were characteristic of parents of children who showed oppositional behaviors.
Internalizing disorders in young children include depression (withdrawal, persistent sadness) and anxiety (Tandon et al., 2009). They may occur simultaneously with and/or independently of externalizing disorders (e.g., noncompliance, aggression, coercive behaviors directed at the environment and others) (Dishion and Snyder, 2016). Studies focusing exclusively on the causes of internalizing disorders in young children are relatively limited. However, the results of the available studies lead to similar conclusions about the relationships among training, changes in parenting practices, and child internalizing problems. First, there is evidence that parental behaviors matter for child emotional functioning. Specifically, parents' sense of personal control and behaviors such as autonomy granting are inversely related to child anxiety in cross-sectional research (McLeod et al., 2007). Similarly, in another nonexperimental study, Duncombe and colleagues (2012) show that inconsistent discipline, parents' negative emotion, and mental health are related to child problems with emotion regulation. Second, there is evidence that parent training interventions can modify the parenting practices that matter. Third, some parent training interventions have positive effects on children's emotional functioning. In a review of randomized controlled studies of the effects of group-based parenting programs on behavioral and emotional adjustment, Barlow and colleagues (2010) found significant effects of the programs on parent-reported outcomes of children under age 4. Herbert and colleagues (2013) conducted a randomized clinical trial of parent training and emotion socialization for hyperactive preschool children in which the target outcome was emotion regulation. Not only did the intervention group mothers report lower hyperactivity, inattention, and emotional lability in their children, but also changes in children's functioning were correlated with more positive and less negative parenting and with less verbosity, greater support, and use of emotion socialization practices on the part of mothers.
With respect to social competence, a number of studies point to a relationship with parenting practices and suggest that parent training may have an impact on both parenting practices related to and children's development of social competence. An experimental evaluation of the Incredible Years Program (discussed further in Chapter 5), for instance, found that parent training contributed to improved parenting practices, defined as lower negative parenting and increased parental stimulation for learning (Brotman et al., 2005), which, in turn, are related to children's social competence. Gagnon and colleagues (2014) found that preschool children with a combination of reactive temperament and authoritarian parents demonstrated low social competence (high levels of disruptive play and low levels of interactive play). In a community trial by Havighurst and colleagues (2010), training focused on helping parents tune in to their own and their children's emotions resulted in significant improvement in the parents' emotion awareness and regulation, as well as the practice of emotion coping. The intervention decreased emotionally dismissive beliefs and behaviors among parents, who also used emotion labels and discussed the causes and consequences of emotions with their children more often than was the case prior to the training. The program improved parental beliefs and relationships with their children, and these improvements were related to reductions in child behavior problems (Havighurst et al., 2010).
Practices to Stimulate Cognitive Development
As explained in the National Research Council (2000) report How People Learn: Brain, Mind, Experience, and School, individuals learn by actively encountering events, objects, actions, and concepts in their environments. For an individual to become an expert in any particular knowledge or skill area, he or she must have substantial experience in that area which is usually guided (Dweck and Leggett, 2000; National Research Council, 2000). As children's first teachers, parents play an important role in their cognitive development, including their acquisition of such competencies as language, literacy, and numerical/math skills that are related to future success in school and society more generally. Enriching and stimulating sets of experiences for children can help develop these skills.
Evidence of the potential importance of parenting for language development is found across studies of parent talk. This research offers compelling correlational evidence that providing children with labels (e.g., for objects, numbers, and letters) to promote and reinforce knowledge, responding contingently to their speech, eliciting and sustaining conversation with them, and simply talking to them more often are related to vocabulary development (Hart and Risley, 1995; Hirsh-Pasek et al., 2015; Hoff, 2003). In addition to the frequency of talking with children, research is beginning to show that the quality of language used by parents when interacting with their children may matter for children's vocabulary development. Studies using various types of designs have shown that children whose fathers are more educated and use complex and diverse language when interacting with them develop stronger vocabulary skills relative to other children (Malin et al., 2012; Pancsofar and Vernon-Feagans, 2006; Rowe et al., 2004).
Language development studies have found that providing an instructional platform in a child's early language experience, such as offering a social context for communication and asking more “what,” “where,” and “why” questions, is associated with language acquisition (Baumwell et al., 1997; Bruner, 1983; Leech et al., 2013). Similar findings are provided by experimental research on dialogic reading, in which adults engage children in discussion about the reading material rather than simply reading to them (Mol et al., 2008; Whitehurst et al., 1988). A meta-analytic review of 16 interventions by Mol and colleagues (2008) showed that, relative to reading as usual, dialogic reading interventions, especially use of expressive language, were more effective at increasing children's vocabulary. The effect was stronger for children ages 2-3 and more modest for those ages 4-5 and those at risk for language and literacy impairment (Mol et al., 2008).
Frequency of shared book reading by mothers and fathers is linked to young children's acquisition of skills and knowledge that affect their later success in reading, writing, and other areas (Baker, 2014; Duursma et al., 2008; Malin et al., 2014). Studies demonstrate that through shared book reading, young children learn, among other skills, to recognize letters and words and develop understanding that print is a visual representation of spoken language, develop phonological awareness (the ability to manipulate the sounds of spoken language), begin to understand syntax and grammar, and learn concepts and story structures (Duursma et al., 2008; Malin et al., 2014). Shared literacy activities such as book reading also expose children to new words and words they may not encounter in spoken language, stimulating vocabulary development beyond what might be obtained through toy-play or other parent-child interactions (Isbell et al., 2004; Ninio, 1983; Whitehurst et al., 1988). Regular book reading also may play a role in establishing routines for children and shaping wake and sleep patterns, as well as provide them with knowledge about relationships and coping that can be applied in the real world (Duursma et al., 2008).
Children of low socioeconomic status and minority children frequently have smaller vocabularies relative to children of higher socioeconomic status and white children, and these differences increase over time (Markman and Brooks-Gunn, 2005). Some experts have theorized that this differential arises from variations in “speech cultures” of families, which are linked to socioeconomic status and race/ethnicity. The middle- and upper-class (primarily white) speech culture is associated with more and more varied language and more conversation, which contributes to bigger vocabularies and improved school readiness among children in these homes (Hart and Risley, 1999). Little research has focused on whether reducing these variations would help close the racial/ethnic gap in school readiness, however (Markman and Brooks-Gunn, 2005). Relative to their middle- and upper-class, mainly white, counterparts, low-income and immigrant parents are less likely to report that they read to their children on a regular basis and to have books and other learning materials in the home (Markman and Brooks-Gunn, 2005). Besides culture, this difference may be due to such factors as access to books (including those in parents' first language), parents' own reading and literacy skills, and erratic work schedules (which could interfere with regular shared book reading before children go to bed, for example).
As discussed in Chapter 4, limited experimental research suggests that interventions designed to promote parents' provision of stimulating learning experiences support children's cognitive development, primarily on measures of language and literacy (Chang et al., 2015; Garcia et al., 2015; Mendelsohn et al., 2005; Roberts and Kaiser, 2011). In one study, for example, interactions between high-risk parents and their children over developmentally stimulating, age-appropriate learning material (e.g., a book or a toy), followed by review and discussion between parents and child development specialists, were found to improve children's cognitive and language skills at 21 months compared with a control group, and also reduced parental stress (Mendelsohn et al., 2005).
Early numeracy and math skills also are building blocks for young children's academic achievement (Claessens and Engel, 2013). To instill early math skills in young children, parents sometimes employ such strategies as playing with blocks, puzzles, and legos; assisting with measuring ingredients for recipes; solving riddles and number games; and playing with fake money (Benigno and Ellis, 2008; Hensen, 2005). Such experiences may facilitate children's math-related competencies, but compared with the research on strategies to foster children's language development, the evidence base on how parenting practices promote math skills in young children is small.
A growing literature identifies general aspects of home-based parental involvement in children's early learning—such as parents' expectations and goals for their children, parent-child communication, and support for learning—that appear to be associated with greater academic achievement, including in math (Fan and Chen, 2001; Galindo and Sonnenschein, 2015; Ginsburg et al., 2010; Jeynes, 2003, 2005). More work is needed, however, to distill specific actions parents can take to promote math-related skills in their young children. At the same time, as noted earlier, some parents appear to be reluctant to engage their children in math learning—some because they lack knowledge about early math and may engage in few math-related activities in the home relative to activities related to language, and some because they view math skills as less important than other skills for their children (Blevins-Knabe et al., 2000; Cannon and Ginsburg, 2008; Vukovic and Lesaux, 2013). Given the demonstrated importance of early math skills for future academic achievement and the persistent gap in math knowledge related to socioeconomic status (Galindo and Sonnenschein, 2015), additional research is needed to elucidate how parents can and do promote young children's math skills and how they can better be supported in providing their children with these skills.
Finally, there is some evidence for differences across demographic groups in the United States with respect to parents' use of practices to promote children's cognitive development. Barbarin and Jean-Baptiste (2013), for example, found that poor and African American parents employed dialogic practices less often than nonpoor and European American parents in a study that utilized in-home interviews and structured observations of parent-child interactions.
Contingent Responsiveness of Parents
Broadly defined, contingent responsiveness denotes an adult's behavior that occurs immediately after and in response to a child's behavior and is related to the child's focus of attention (Roth, 1987). Dunst and colleagues (1990) argue that every time two or more people are together, there is a communicative exchange in which the behavior (nonverbal or verbal) affects the other person, is interpreted, and is responded to with a “discernible outcome” (p. 1). Such communication exchanges between parents and their children are considered foundational for building healthy relationships between parents and children, as well as between parents (Cabrera et al., 2014).
Within the multiple relationships and systems that surround parents and children, the quality of the relationship they share is vital for the well-being of both (Bronfenbrenner and Morris, 1998). The science is clear on the importance of positive parent-child relationships for children. Emotionally responsive parenting, whereby parents respond in a timely and appropriate way to children's needs, is a major element of healthy relationships, and is correlated with positive developmental outcomes for children that include emotional security, social facility, symbolic competence, verbal ability, and intellectual achievement (Ainsworth et al., 1974). The majority of children who are loved and cared for from birth and develop healthy and reciprocally nurturing relationships with their caregivers grow up to be happy and well adjusted (Armstrong and Morris, 2000; Bakermans-Kranenburg et al., 2003). Conversely, children who grow up in neglectful or abusive relationships with parents who are overly intrusive and controlling are at high risk for a variety of adverse health and behavioral outcomes (Barber, 2002; Egeland et al., 1993).
The development of health-promoting relationships between parents and their children is rooted in evolutionary pressures that lead children to be born wired to interact with their social environment in ways that will ensure their survival and promote their eventual development (Bowlby, 2008). Through reaching out, babbling, facial expressions, and gestures, very young children signal to caregivers when they are ready to engage with them. Caregivers may respond by producing similar vocalizations and gestures to signal back to infants that they have heard and understood (Masataka, 1993). Cabrera and colleagues (2007) found that children of fathers who react to their behavior in a sensitive way by following their cues, responding, and engaging them are more linguistically and socially competent relative to children of fathers who do not react in these ways (Cabrera et al., 2007).
This “serve and return” interaction between caregivers and children, which continues throughout childhood, is fundamental for growth-promoting relationships (Institute of Medicine and National Research Council, 2015; National Research Council and Institute of Medicine, 2000). A consistent give and take with responsive caregivers provides the child with tailored experiences that are enriching and stimulating; forms an emotional connection between caregiver and child; builds on the child's interests and capacities; helps the child develop a sense of self; and stimulates the child's intellectual, social, physical, and emotional and behavioral growth (Institute of Medicine and National Research Council, 2015; National Research Council and Institute of Medicine, 2000). This give and take is particularly important for language development. It is believed that through this process, the child learns that she or he is loved and will love others in return, and that she or he is accepted and cared for and will also eventually accept and care for others.
For infants, social expectations and a sense of self-efficacy in initiating social interactions are influenced by their early interactions with their caregivers. McQuaid and colleagues (2009) found that mothers' contingent smiles (i.e., those in response to infant smiles) in an initial interactive study phase predicted infant social bids when mothers were still-faced in a subsequent study phase, a finding consistent with results of earlier research (Bigelow, 1998). The adult's response to the child's overtures for interaction needs to be contingent on the child's behaviors. Infants' spontaneous vocalizations are characterized by pauses that enable caregivers to respond vocally. Children who have experience with turn taking are able to vocalize back to the caregiver in a synchronized manner (Masataka, 1993). Young children's social and emotional development is influenced by the degree to which primary caregivers engage them in this kind of growth-promoting interaction (Cassidy, 2002).
As described in Chapter 1, securely attached infants develop basic trust in their caregivers and seek the caregiver's comfort and love when alarmed because they expect to receive protection and emotional support. Infants who trust their caregivers to respond to their needs in a sensitive and timely manner are able to explore and learn freely because they can return to their “safe base” if they encounter unfamiliar things and events (Bowlby, 2008; Cassidy, 2002
Children’s health is determined by the interaction of a multitude of influences, reflecting complex processes. We divide these influences into biological, behavioral, and environmental (physical and social) even though our model of children’s health views their effects as highly intertwined and difficult to isolate. This chapter provides a summary of published literature and a framework for understanding those influences.
Biological influences as discussed in this chapter include genetic expressions, prenatal influences, as well as biological constraints and possibilities created by perinatal and postnatal events plus prior states of health. Behavioral influences include the child’s emotions, beliefs, attitudes, behaviors, and cognitive abilities that affect health outcomes. Environmental influences are wide-ranging and include infectious agents, toxins such as lead and air pollution, and social factors such as loving interactions with caregivers, socioeconomic resources in the family and community, and peer relationships, segregation, racism, culture, the availability and quality of services, and policies that directly or indirectly affect these other interactive influences (see Box 3-1).
Organization of Influences on Children’s Health. Children’s biology Children’s behavior
The role and effect of biological, behavioral, and environmental influences change as children grow. For example, a pharmacological agent like thalidomide is highly toxic within a narrow window during pregnancy but not afterward, an attachment to a caring adult is especially critical during infancy, and peer influences appear to grow steadily from toddlerhood through adolescence. Even within a childhood stage, health influences can act in very different ways because of the differing cultural interpretations that families attach to them.
While biology, behavior, and environmental categories are useful for organizing our discussion, it is important to understand that healthy development is not the product of single, isolated influences or even types of influences. Warm and nurturing parenting is an important family influence, but prematurity or visual impairment can make an infant unresponsive to a mother’s initial nurturing. Mothers may react with apathy or disinterest, which produces even more withdrawal on the part of the infant (Lozoff, 1989). While simplified schematics or models help to organize understanding of the influences on children’s health both during childhood and beyond, life is not as simple as these models suggest.
One caveat should be kept in mind in reading through the following review of evidence. Few of the cited studies drew their evidence from randomized experiments. And few if any of the nonexperimental studies included all relevant variables in their data and analyses. Thus, the findings reported in these studies are likely to suffer from exclusion of potentially important categories of influences, so that the associations that are reported as being important may be due to their associations with a more important or equally important characteristic, or due to interactions with other types of factors so that their effect may be manifested primarily or only in certain population groups. A related problem is that few of the cited studies include data that represent the whole population of children. Thus, the findings that are reported as significant may be significant only in the population studied or similar populations. Nonetheless, the committee found the evidence to be sufficiently compelling to warrant inclusion when there was a plausible, well-supported connection between the influence and health.
Moreover, inferences about the relative importance of the variety of influences are heavily dependent on the nature of the theoretical models that underlie statistical analysis. If more proximal influences are mixed with more distal ones, they may appear to have stronger effects, even in situations in which more distal factors are operating on a multiplicity of proximal influences and therefore have cumulatively greater effect overall. Thus, future research should adapt more appropriate pathway techniques to help to sort out the patterns by which the influences interact to produce different states of health.
Finally, the relative lengths of the following sections are not meant to signify the relative importance of the influences. For some, the prevalence is less well known than for others. From the viewpoint of influences on population or sub-population health, the relative frequency of the different influences is at least as critical as the degree of the risk that they pose to individuals. Additional research is needed to refine understanding of the relative contribution of each of the influences and the relevance of each across a variety of social and cultural groups.
A child’s biology determines how physiological processes unfold and how organ systems adapt to outside influences. Biological response patterns, including responses to stress, novel situations, and primary relationships, can directly and indirectly influence other biological, cognitive (learning), and behavioral processes. The term “biological embedding” has been used to describe how the external environment influences and shapes the biological environment (including the central nervous system), which in turn changes the way the individual interacts with the external environment (Hertzman, 1999).
DNA provides the blueprint for life. The units of heredity, or genes, are specific sequences of DNA that code for proteins that affect the particular physiology and anatomy of an individual. All cells contain the full array of genes but, depending on the cell type, some are expressed while others are not; for example, certain genes coding for proteins in the retina are expressed in the cells of the eye, but not in the pancreas cells.
Disruptions in genes can be caused by events before, during, or after conception and may produce disorders immediately or later in life. A parent can pass on a defective or abnormal gene or set of genes, a malfunction can occur during combination of maternal and paternal DNA, or exposure to an outside substance or condition can occur after conception that alters the genes in the fetus. Physical and social environments (e.g., family, community, school, culture) interact with and influence these biological processes.
Influences of Genes on Responses to Different Environments
Classically, genes have been considered to be the “instructions” for building proteins, although it is clear now that they have other functions as well. A gene may affect health as a result of the interaction of its protein product with another aspect of a child’s biology. The combinations of these interactions may result in an enhanced, worsened, or inconsequential change in health status. For example, sometimes an alteration in the gene (i.e., mutation) is identified due to the presence of a particular disease state, or it can be deduced that an individual with the mutation has a high probability of developing a particular disease. Understanding the biological pathway of the disease and its interactions with other biological processes facilitates treatment options by modifying the causal path. In the case of Huntington’s disease, for example, the disorder appears to be in part mediated by glutamate excitotoxicity; giving patients a substance that blocks this effect (glutamate receptor antagonists) interrupts this pathway and may retard the manifestation of the disease (Ferrante et al., 2002). The influence of genes on health always exists in an environmental context; in the next sections we describe how genes affect behavior and the physical and social environments.
Genes and Behavior. That genes affect behavior has been amply demonstrated in honeybees (Ben-Shahar et al., 2002) and higher animals (Ruby et al., 2002; Chester et al., 2003; Hendricks et al., 2003). Examples in humans are being rapidly discovered, including genes that influence the relationship between exposure to trauma and susceptibility to posttraumatic stress disorder (Stein et al., 2002), genetic polymorphisms that protect against alcoholism (Wall, Carr, and Ehlers, 2003), mutations that result in sleep disorders (Wijnen et al., 2002), and several genes that are associated with simple phobias (Gelernter et al., 2003).
Genes and the Physical Environment. The physical environment includes ubiquitous agents (e.g., ultraviolet light, amino acids and sugars in the diet, noise, speech) and somewhat less universally encountered ones (e.g., loud music, medications, pollutants). Some genes result in poor outcomes following common environmental exposures (e.g., phenylketonuria with phenylalanine, galactosemia with galactose, xeroderma pigmentosa with ultraviolet light exposures). Individuals with these genotypes are likely to be affected by the disease because they have a high chance of being exposed to the physical environmental agent. In some cases, the physical environment can be modified to improve outcomes (e.g., a phenylalanine-free or galactose-free diet may improve IQ, no sunlight or ultraviolet exposure may reduce skin cancers). There are also gene alterations resulting from uncommon physical environmental exposures that affect health. Examples include a higher risk of lung cancer in individuals lacking glutathione S-transferase mu who smoke (Perera et al., 2002) and noise-induced hearing loss in some individuals exposed to high levels of noise—the gene or genes in this case are just being discovered (Kozel et al., 2002). These genes are known as susceptibility genes. An example of a positive susceptibility gene to a physical environmental agent may be that for perfect pitch. It appears that individuals with exposure to music and a family history of perfect pitch are more likely to acquire perfect pitch (Alfred, 2000).
Genes and the Social Environment. The identification of genes that confer susceptibility to adverse or beneficial responses following exposure to diverse social environments has only just begun. In one study, abused children with a genotype conferring high levels of neurotransmitter-metabolizing enzyme monoamine oxidase A expression were less likely to develop antisocial problems in adulthood (Caspi et al., 2002). The risk of developing alcohol abuse or dependence also appears to have both a genetic susceptibility and a family influence (Macciardi et al., 1999; McGue et al., 2001), as does the risk for relapse and poor outcomes with schizophrenia (Campbell, 2001).
Characteristics of Gene-Environment Interactions
The expression of certain genetic characteristics depends on the environment in which they occur. Thus, gene expressions that lead to a disease in one context may not lead to a disease, or may result in a different disease, in another context (Holtzman, 2002). Inheriting a single copy of the hemoglobin S gene makes an individual resistant to malaria (Aidoo et al., 2002). However, inheriting two such genes gives the individual sickle cell anemia, a severe disease. Outside of malaria-endemic areas, sickle cell trait, the inheritance of one copy of hemoglobin S, has no known adaptive benefit and may be maladaptive. A single cystic fibrosis gene has been postulated to be protective against diarrheal diseases such as cholera, conferring a survival advantage to individuals who carry one copy of the gene (Rodman and Zamudio, 1991). However, individuals with two such genes have cystic fibrosis, a severe disorder with altered pulmonary and gastrointestinal function. Other examples of genes with positive influence also exist in given environments. The gene or genes that confer protection from cancer (Gonzalez et al., 2002; Reszka and Wasowicz, 2002) have been described.
Genes may confer susceptibility only during a specific span of time, referred to as a critical period. For example, 20 percent of children are extremely sensitive to thalidomide during a critical 15-day period from day 20 to day 35 of gestation, although the gene or genes responsible for this enhanced sensitivity have not yet been identified (Finnell et al., 2002). Presumably there are narrow windows of rapid development throughout childhood, including puberty, but critical windows of sensitivity to disruption have not been adequately described (Selevan et al., 2000). The complex interrelationships between genetics and environmental stimuli are not clearly defined and are an active area of current research.
Understanding of the genome has rapidly expanded the study of the ways in which genes interact with diverse influences (e.g., physical and social environments) to affect health. Expression of genes (the amount of the protein encoded for by the gene) has a profound influence on the health of the individual. Gene expression is determined by many factors, such as promoters, regulators, mutagens/carcinogens/teratogens, X-inactivation, message stability, rate of protein degradation, prior exposures, all of which are affected by the environment. Interactions between genes and the environment influence different physiological pathways and adaptation (Holtzman, 2001) and may lead to adaptive or maladaptive phenotypes. An interesting example is the hygiene theory of childhood asthma, which postulates that children living in hygienic, low-pathogen environments develop an imbalance between two types of immune cell classes (TH1 and TH2). Children with an imbalance of TH1 and TH2 are more likely to develop allergies and asthma when confronted with allergens. When children live in low-hygiene, high-pathogen environments, they develop a strong system of immune regulators (a balance between TH1 and TH2 cells), and they are less likely to develop allergies or asthma (Yazdanbakhsh et al., 2002). Children living on farms or in homes with at least two cats or dogs in the first year of life have been shown to have significantly lower rates of allergic sensitization tested at 6–7 years (Ownby et al., 2002).
Healthy development depends on gene expression being responsive to changes in the environment. For example, the radical change in the environment at birth is responsible for changing the expression of genes to enable the baby to make the transition from intrauterine to extrauterine life. These include the production of proteins that close the ductus arteriosus (Kajino et al., 2001), alter lung liquid absorption (Matalon and O’Brodovich, 1999), produce barrier function in the skin (Harpin and Rutter, 1983), produce immunoglobulins, and alter gene expression in brain development. Thus, to be healthy, newborns must make profound changes in gene expression as they transition from intrauterine to extrauterine environments.
Converging findings from genetics and molecular biology demonstrate that a host of internal and external signals can stimulate or inhibit gene expression, including subtle factors such as the light-dark cycle (Hegarty, Jonassent, and Bittman, 1990) and tactile stimulation (Mack and Mack, 1992). This pattern of contingency is now recognized as part of the normal process of development in embryology and developmental biology, and there is a growing body of literature demonstrating how factors, including internal neural and hormonal events and external sensory events, activate or inhibit gene expression during individual development (see Davidson, 1986, 2001; Gilbert, 2000; Holliday, 1990).
Chemicals in the environment (air, water, dirt, dust, food) move into the body across such biological barriers as skin, lungs, and the gastrointestinal system. Exposure is considered to be contact of the agent with the biological barrier; following exposure, the agent crosses the barrier and is found inside the body (the internal dose). After uptake or absorption across the barrier, chemical agents (including drugs) are distributed throughout the body, metabolized, and eliminated (U.S. Environmental Protection Agency, 2003; Atkinson et al., 2001).
The rate of elimination varies substantially for different agents; some are eliminated in a matter of minutes; others may be found in the body for years following exposure. The amount of chemical/biochemical/vitamin/mineral stored or measured in the body is called the “body stores” or “body burden” of that agent. The committee has adopted the term “body burden” in this report. Body burdens of a chemical or drug represent the amount of cumulative exposure and, in some instances, can be transferred to another individual (e.g., from a mother to the fetus or infant through the placenta or in breast milk).
Body burdens can improve or harm health, based on their biological characteristics and presence during certain periods of development. Maternal body burdens of either lead or polychlorinated biphenyls (PCBs) impair the cognitive function of offspring if present during critical periods during fetal development (Gomaa et al., 2002; Lai et al., 2002). A body burden of lead in the bones of young children has been associated with poor social behavior (Needleman et al., 2002; Wald et al., 2001), poor cognitive performance or development (Lanphear et al., 2003; Rogan and Ware, 2003), and impaired pubertal progression (Selevan et al., 2003). The relative impact of body burdens varies with developmental stage. Relatively lower body burdens of organic mercury will reduce cognitive development in young children more than at older ages (U.S. Environmental Protection Agency, 2000c; National Research Council, 2000).
Some body burdens can have positive impacts on healthy development. For example, maternal body burdens of folate during the early first trimester of pregnancy significantly reduce the risk of a baby with a neural tube defect (Wald et al., 2001). Adolescents with higher levels of folate also have a significantly decreased risk of juvenile hypertension (Kahleova et al., 2002), and adults with high folate stores appear to be at substantially lower risk of cardiovascular disease (Wald, Law, and Morris, 2002). Some body stores that are beneficial at lower levels can become harmful at higher levels: a baby’s appropriate body burdens of iron will improve cognitive outcome, but an inappropriately high body burden of iron potentiates oxidative stress (Rao and Georgieff, 2001) or can cause iron overload disease. Low maternal or fetal levels of vitamin A are associated with developmental disease, as are high levels.
The impact of some body burdens vary across time and, to be understood, must be assessed at different times. For example, a maternal body burden of PCBs causes exposure to both the fetus and to the newborn via breast milk. Body burdens at one time may also impact measures of health in later time frames. A child who has received treatment for Hodgkin’s lymphoma, increasing the genotoxic body burden, is at risk for secondary cancers (Hack et al., 2002).
While not without controversy (Huxley et al., 2002), there is a growing literature on the potential role of “perinatal programming,” referring to the processes in which specific influences during critical or sensitive periods of development can have lifetime consequences by altering metabolic pathways and other physiological systems. This appears to be a special case of the more general phenomenon of how environmental influences can be embedded in biology during critical and sensitive periods of development.
In humans, the relationship between fetal growth, postnatal growth, and the risk of such diseases as hypertension, coronary heart disease, and non-insulin-dependent diabetes have been frequently studied (Bertram and Hanson, 2002; Barker, 1998). Both human epidemiological and animal experimental studies support the hypothesis that relative undernutrition in the fetus results in significant and relatively permanent changes in important physiological systems (Nathanielsz, 1999). Perinatal programming indicates that sensitive or critical periods of development may have lifelong effects and influence the development of chronic diseases later in life (Ingelfinger, 2003). However, it does not discount the potential effect of the external environment (Seckl, 1998; Ingelfinger and Woods, 2002; Falkner, 2002; Roseboom et al., 2001) in modifying the effects.
Fetal undernutrition is believed to induce persistent changes in several metabolic pathways, but the exact mechanisms are only now being pieced together through a range of animal experiments and human measurement studies (Seckl, 1998; Barker, 1998). Because it is likely that events occurring at other times modify prior influences, there is a growing interest in understanding the predisease pathways and biological changes that occur prior to the recognition of a vast array of clinical outcomes. Currently many of these predisease markers are either below current limits of detection or produce changes that are not currently measured on a routine basis (Lucas et al., 1999; Keller et al., 2003; Ingelfinger, 2003).
Examples of such programming during particular sensitive or critical periods of development are coming to light. For example, low numbers of nephrons are associated with hypertension, and it has been shown that individuals whose mothers experienced severe protein-calorie malnutrition during the third trimester, when nephron development takes place, are most at risk of hypertension (Roseboom et al., 2001; Keller et al., 2003). Outcomes associated with programming early in life may also promote health. For example, rats receiving high levels of licking and grooming as pups are less fearful compared with rats that received low levels of licking and grooming (Francis et al., 2002). The mechanism for this change in behavioral programming appears to be the influence of maternal licking on gene expression during a critical period of development and subsequent changes in the development of synaptic receptor sites for specific neurotransmitters (Francis et al., 1999).
Similar environmental influences on the development of behavioral pathways have been described in rhesus monkeys (Champoux et al., 2002), and studies of premature human infants show substantially greater increases in body weight after introduction of massage therapy (Field, 2002). In contrast, disruption of maternal bonding during infancy has been shown to have profound negative effects on later relationships (National Research Council and Institute of Medicine, 2000).
As used in this report, behavior refers to a child’s emotions, beliefs, cognitions, and attitudes, as well as his or her overt behaviors. Some behaviors are planned and deliberate; others are reflexive, impulsive, and contingent on environmental circumstances. A child’s emotions, beliefs, and attitudes affect health, principally through the way they modify a child’s explicit and overt behaviors, such as his or her health and life-style choices. These in turn alter the child’s eventual health outcomes. Examples include social and interactional behaviors (e.g., compliance with parental requests, peer interactions), health preventive behaviors (e.g., avoiding smoking, driving with a seat belt, choosing good friends), or illness-management-related behaviors (e.g., behavioral adherence with a treatment regimen or health care appointments).
Health-related behaviors may be health promoting (those that increase the likelihood of future health, such as regular balanced diet and exercise) or health impairing (those that adversely cause actual morbidity or mortality, such as smoking, drinking, or reckless driving). A body of recent research suggests how these behaviors develop and describes the role of family, peers, and social environment, including media, in shaping this developmental process (Tinsley, 2003). While behaviors like smoking, drinking, and exercise are known to affect later health, it is not clear how these behaviors develop in childhood (McGinnis and Foege, 1999).
Often these health behaviors are considered proxies for health, even though they may not necessarily constitute health per se. Some health policies attempt to change youth behaviors that are thought to affect health. An example is the requirement for regular school attendance, which may both reflect current health and exert effects on a given child’s likelihood of future health.
Behavioral influences on children’s health are often reciprocal, both influencing and influenced by parents, peers, and others. For example, parenting style, family traditions, and peer influences affect not only fairly simple youth behaviors, such as compliance with behavioral requests or participation in health prevention programs (Patterson and Fisher, 2002), but also more complex behaviors, such as participation with disease management regimens. This section focuses on the internal psychological factors that underpin children’s behavior, with implications for subsequent health outcomes.
Emotions, Attitudes, and Beliefs
In addition to the influence of explicit behaviors on health, a child’s internal emotional, attitude motivation, or belief states may exert effects on health. For example, research on both adults and children has shown direct relationships between internal attitudinal and personality factors and health outcomes, perhaps through mechanisms that link internal emotions, attitudes, and beliefs with stress reactions and immune responses (Berry and Worthington, 2001; Herbert and Cohen, 1993; Kiecolt-Glaser, 1999, Lawler et al., 2000). Thus, external events perceived as stressful by a child may function as triggers for an asthma or inflammatory bowel disease flare, over and above any biological exposure or adherence to therapy (Rietveld and Prins, 1998; Santos et al., 2001). Presumably such effects are conveyed through a child’s emotional arousal states, which in turn result in physiological changes, such as increased pulse and elevated blood pressure, glycemic, and immune responses. This research has solid empirical support in both the adult human and animal research fields (McEwen, 1998; Seeman et al., 1997), but it is less firmly established for children.
The hallmark of childhood is the constant exposure to new developmental challenges. As children acquire new physical and cognitive skills and experiences, their behaviors change. They explore, practice, and experiment and as a result they change and are changed. The resulting behaviors are both manifestations of their health and have significant implications for it. At each new exposure, the child may respond in a variety of ways that in turn unleash a variety of reactions in his or her caregiver and in others around him.
From birth, infants recognize, prefer, and are soothed preferentially by their mother’s voice (Mehler et al., 1978; DeCasper and Fifer, 1980). They suckle more in response to it (Mehler et al., 1978), and mothers in turn are gratified by their ability to sooth their children (Klaus et al., 1972). Thus the beginnings of attachment are initiated. As an infant continues his or her explorations and trials, which themselves influence health, they produce reactions from caretakers that in turn further affect the infant’s behavior and health. One of the first developmental challenges faced by an infant is adaptation to extrauterine life. Low-birthweight infants experience more difficult transitions and are more likely to be fussy during social interactions and less likely to smile and vocalize (Beckwith and Rodning, 1992; Barnard and Kelly, 1990). These infant reactions in turn impose stresses on the parent, which may affect the child’s health through impaired attachment. If the parent responds in a fashion that induces further stress in the infant, the increased stress in turn may affect the infant’s ability to secrete adequate amounts of growth hormone (Skuse et al., 1996), potentially leading to growth impairment or failure to thrive.
Attempts to make this transition are met with a variety of parental and cultural responses, all of which influence infants in ways that facilitate or impede their development. Nearly a quarter of infants respond to new stimuli in a negative fashion (Kagan et al., 1998); their early infancy imposes a series of challenges that are especially daunting and many are found to still be socially wary and exhibit evidence of physiological stress at age 6 years (Kagan et al., 1987).
Emotional development and the establishment of social relationships are among the greatest challenges of infancy and early childhood. Emotions are fundamental for human attachments, social interactions, and self-satisfaction. Therefore, the extent to which infants evoke sympathetic and empathetic emotions in others and eventually develop these emotional expressions themselves greatly influences their subsequent health. Children who do not attain these skills are more likely to encounter rejection from caretakers and peers (Dodge et al., 2003; Schultz et al., 2000). The complex interplay of genetics, parenting, and societal reactions illustrates just how precarious the early years are and how central infant behavior is for subsequent health (Rutter, 1998).
Attitudes, Beliefs, and Circumstances
The effects of individual, family, and community attitudes and beliefs on health behavior have been well described. A substantial body of research has been conducted on issues related to adherence to treatment regimens, both among parents of younger children and among adolescents (McQuaid et al., 2003; Volovitz et al., 2000; Davis et al., 2001). This work focused initially on asthma and diabetes and more recently on substance use and HIV/AIDS treatment (Manne, 1998). Current research is informed by several related theoretical models of behavior, all of which take into account youths’ attitudes, beliefs, and subjective perceptions about the risks of negative outcomes, as well as the perceived benefits and difficulties of treatment (Hochbaum, 1956; Ajzen, 1991; Rogers, 1983; Bandura, 1994).
In accordance with these models, data suggest that both parents’ and youths’ attitudes are moderately predictive of subsequent health care behaviors, whether in the context of seizures (Kyngas, 2001; Kyngas et al., 2000), asthma (Kyngas, 1999), diabetes (Wysocki et al., 2000; Ott et al., 2000), or sexual risk avoidance (Stanton et al., 1996; St. Lawrence et al., 1995; Jemmott and Jemmott, 1994).
These conceptual considerations lead directly to specific interventions, such as motivational enhancement strategies to encourage youths’ substance abuse treatment compliance (Carroll et al., 2001), engaging them in sexual risk prevention activities (Stanton et al., 1996; St. Lawrence et al., 1995), and using collaborative goal-setting strategies in enhancing adolescent diabetes self-care (Delamater et al., 2001). In addition, these theories help explain why and how child compliance may be positively (or adversely) affected by peer and family support (LaGreca and Bearman, 2002; LaGreca et al., 2002; Liss et al., 1998), as well as the support available through a good relationship between the youth and his or her health care team (DiMatteo, 2000; Kyngas et al., 2000). The effect of and the need for support may vary as a function of age (Steinberg, 1999).
Research has documented the impact of chronic illness on child and adolescent adjustment (DiMatteo, 2000; Kyngas et al., 2000). Not infrequently, depression, anxiety, low self-esteem, or other adjustment difficulties may ensue as a result of the underlying illness, increasing risk for treatment nonadherence (Wise et al., 2001; Murphy et al., 2001; Davis et al., 2001) or worsening the outcome of the primary illness (Kuttner et al., 1990; Hauser et al., 1990). Available evidence suggests that good communication skills and the development of positive relationships with the clinical team may offset the effects of negative emotions on health care adherence (Buston, 2002; García and Weisz, 2002; Shaw, 2001).
Emotion, Cognition, and External Influences
The importance of cognitive ability and understanding inappropriate health-related behaviors must also be considered. Children’s ability to understand safety rules and health behaviors increases with age (Morrongiello et al., 2001). Over time they acquire the capacity to conceptualize and understand the longer term consequences of their behaviors on their health (Thomas et al., 1997). Conversely, children with developmental disabilities or impaired language ability often show increased difficulties in adhering to necessary behaviors, including health-maintaining ones (Stansbury and Zimmerman, 1999).
While attitudinal, motivational, cognitive, and emotional factors may all exert direct effects on health-related behaviors, the role of environmental factors in these behaviors should not be underestimated. For example, under some circumstances, behavioral factors may contribute less to youths’ actual health care behaviors than making available a more easily used medication, such as a long-acting form of medication in the case of birth control (Stevens-Simon et al., 2001; Omar et al., 2002) or providing more stable living situations in the case of adolescents’ likelihood of adhering to an HIV/AIDS drug regimen (Conanan et al., 2003). In addition, children’s behaviors may directly affect parents’ ability to adhere to a treatment regimen (Searle et al., 2000), just as parental response styles may affect the likelihood of a child’s complying with specific requests (Patterson and Fisher, 2002).
Cultural construction of health and disease may also affect compliance with certain treatments by both parents and children. For example, in many cultures, so-called teething diarrhea is considered to be a normal part of growth and development and thus health-seeking behavior or adherence to treatment regimens for the “illness” would be unlikely (Stanton et al., 1992).
In sum, all these psychological factors, whether a child’s perceptions of peer norms, self-efficacy beliefs, attitudes about health and health care, or level of motivation to pursue specific health care behaviors, contribute to health-related choices and behaviors. With increasing age, children’s behaviors, such as substance use, academic performance, violence, suicide, and auto accidents, constitute a major influence on future health. According to findings from the Global Burden of Disease study, these behavioral aspects of health are likely to exert even greater prominence in coming decades, as behavioral and life-style-related health conditions (e.g., auto accident injuries, consequences of smoking, depression) increase in their relative effect on children’s health and illness (Murray and Lopez, 1996).
Complicating this point, however, is the fact that certain behaviors and emotions can serve both as health influences and outcomes. Determining when a behavior is an influence rather than a health outcome can be difficult, because children’s current behaviors can affect both future behaviors and subsequent health outcomes. Regardless of the classification and especially due to the inability to distinguish behaviors as health influences or outcomes, data on children’s health behavior are an important component of a system that seeks to track child health and health behaviors.
The physical environment affects children’s health by exposing them to a wide variety of external conditions. These include chemical, biological, and physical influences that exert their impact by being taken into the body (e.g., lead, methyl mercury, persistent organic pollutants) or interacting with body surfaces (e.g., ultraviolet light, physical abuse, particulate matter in air pollution) or the senses (e.g., noise, odors). The built environment affects the ways in which children are differentially exposed to some of these influences. Exposure is the sum of all exposure factors over the course of time, including the home, school, child care, and play areas. Exposures during the prenatal period can also affect children’s health.
Although exposures of the ovum or the sperm prior to conception may have profound health effects on a child, including development of an abnormal fetus,1 in this section we focus on prenatal influences. In most cases, exposures of the fetus are from maternal exposure. Exposures of the mother during pregnancy can come from many sources; common sources include maternal occupation, substance use, diet and water consumption, and paraoccupation (occupational chemicals or other hazards brought home by other family members). The strongest workplace exposure associations are lead, mercury, organic solvents, ethylene oxide, and ionizing radiation and poor reproductive outcome, including birth defects (Agency for Toxic Substance and Disease Registry, 1993; Schardein, 2000).
Use of tobacco, alcohol, and illicit drugs also have harmful effects. Tobacco use during pregnancy is a major cause of fetal and newborn morbidity and mortality (small for gestational age, persistent pulmonary hypertension, sudden infant death syndrome, poorer intellectual functioning) (Nicholl, 1989; Golding, 1997; Day et al., 1992; Kline, 1987; U.S. Environmental Protection Agency, 1992; Bearer et al., 1997). Heavy drinking during pregnancy is the cause of fetal alcohol syndrome (FAS), the leading known cause of mental retardation (Abel and Sokol, 1987; Sokol, Delaney-Black, and Nordstrom, 2003). Conservative estimates place the incidence of FAS at 0.33/1,000 live births (Abel and Sokol, 1991). More common effects include alcohol-related birth defects, alcohol-related neuro-developmental defects, and subtle effects on a variety of behavioral, educational, and psychological tests resulting from low to moderate levels of drinking during pregnancy (Institute of Medicine, 1996). While the effects of maternal prenatal use of cocaine, opiates, and methamphetamines on infant cognitive development and behavior remain controversial (owing to confounding environmental factors) (Bays, 1990; Tronick and Beeghly, 1999), the effects on maternal-infant interactions are more established (Breiter et al., 1997; Singer, 2000).
There are multiple short critical periods during the development of a fetus when a short, acute exposure may cause a problem. For this reason, exposures need to be tracked as highs and lows on a daily basis rather than as monthly averages. For example, water quality is regulated by monthly averages. However, a daily peak may exceed a threshold of concern and still be within the regulatory limit.
A recent review concluded that neural tube defects and small-for-gestational-age births are moderately associated with contaminated drinking water (i.e., trihalomethanes) (Bove et al., 2001). Oral clefts, cardiac defects, and complete nasal obstruction (choanal atresia) were found in studies evaluating trichloroethylene-contaminated drinking water (Bove et al., 2001). Food may also contain environmental teratogens. A well-known example is the epidemic of cerebral palsy that followed maternal consumption of fish contaminated with organic mercury in Minimata Bay, Japan (Harada, 1978).
Characterization of exposures over time depends on developmental stage and the mechanism by which the agent produces its effect (EPA exposure guidelines, 2003). Multiple types of exposure may interact to produce their effect by the same mechanism, as for example the exposure to multiple insecticides that interfere with cholinesterases (National Research Council, 1993). Children have unique susceptibilities to chemical exposures (see Box 3-2).
Children’s Unique Susceptibility to Chemical Exposures. Children are more susceptible than adults to chemical exposures, and their exposure varies, depending on their physical location, breathing zones, oxygen consumption, types and amount of (more...)
Six outdoor air pollutants are regulated by the Clean Air Act: ozone, respirable particulate matter, lead, sulfur dioxide, carbon monoxide (CO), and nitrogen oxides. The effects of repeated or long-term exposure to outdoor air pollutants on the developing lungs of children are not well understood. Indoor air pollution, which is generally not regulated (one notable exception being laws prohibiting indoor smoking in public spaces), results primarily from (1) the products of combustion, such as CO, nitrogen dioxide, particulates, and sulfur dioxides; (2) volatile organic compounds, such as formaldehyde, benzene, and trichloroethylene; (3) the products of tobacco smoking (approximately 3,800 chemicals); and (4) molds.
Health effects from these diverse indoor air pollutants include respiratory irritation with cough and wheezing, exacerbation of asthma, allergic responses, cancer, and central nervous system effects (headache, nausea) (American Academy of Pediatrics, 2003). Exposure to asbestos, leading to lung cancer, is also a concern due to the prevalence of asbestos in schools and some homes (U.S. Environmental Protection Agency, 1987; American Academy of Pediatrics, 1987).
Some water pollutants are biological agents, some are chemical agents, and some are radionuclides (physical agents). Biological agents generally come from fecal contamination and include such bacteria as salmonella and E. coli, such viruses as hepatitis A and rotavirus, and such parasites as Cryptosporidium parvum. Chemicals in water include such metals as lead, mercury, and arsenic, such natural toxins as Pfiesteria toxins, organic chemicals including pesticides, PCBs, trichloroethylene, and chlorination by-products, such inorganic ions as nitrates, and such radionuclides as radon. Systems affected by these contaminants include the central nervous system, the gastrointestinal system, and the hematological system. Many of these chemicals are also carcinogens. Children have been found to be at higher relative risk of gastrointestinal illness from contaminated water (Wade et al., 2003). In addition, children are both more highly exposed and more susceptible to the contaminants found in water. For example, lead in drinking water was found to be the cause of lead poisoning in several infants whose blood lead exceeded 10 mcg/dl (Baum and Shannon, 1997; Shannon and Graef, 1992).
Food contaminants can be broadly categorized as either pathogenic or toxic. Pathogenic agents include bacteria, viruses or parasites, bacterial toxins, aquatic organisms that elaborate toxins, and toxins that accumulate in the food chain, such as domoic acid. Toxic chemicals in food can be divided into three categories: (1) pesticides that have been deliberately applied to the food source; (2) colors, flavors, or preservatives deliberately added to food during processing; and (3) chemicals that inadvertently enter the food chain, such as PCBs, heavy metals, and persistent pesticides such as DDT. Particular effects of food contaminants on children include such behavior changes as hyperactivity (Carter et al., 1993) and developmental neurotoxicity from pesticide exposure in food (National Research Council, 1993).
Children also are a demographic subgroup prone to infectious diseases because of their exploratory behavior, lack of prior exposure to most infectious agents, and association with other children. Substantial advances in vaccines have reduced rates of many infectious diseases during the past decades. Nonetheless, infectious agents remain a major threat to children’s health, particularly with the increase in antibiotic resistance among various infectious organisms and the emergence of new infectious agents (i.e., new strains of flu).
Children are highly exposed and susceptible to some infections that are spread by droplets from coughing and sneezing. Respiratory syncytial virus, the leading cause of serious upper and lower respiratory tract infection in infants and children, accounts for 125,000 hospitalizations and 450 deaths annually in the United States, and it may predispose children to asthma later in life. Annual epidemics occur from November to April, and virtually all infants are infected by age 2 (Black, 2003). Cytomegalovirus infection is spread in child care centers through both urine and saliva containing live virus; rates for preschool-age children in the United States range from approximately 5 to 30 percent (Centers for Disease Control and Prevention, 1985). Children are also particularly susceptible to other infectious agents, such as rotavirus and Norwalk virus, salmonella, and E. coli O157:H7, which cause diarrhea and dehydration and sometimes severe complications.
Children are also more highly exposed to vector-borne (e.g., via ticks, fleas) or certain zoonotic (e.g., hosted by dogs, cats, horses) pathogens due to their increased time outdoors, play activities, and behaviors. Vector-borne pathogens include Lyme disease, highest among 5–9-year-olds (Centers for Disease Control and Prevention, 2002a), and Rocky Mountain spotted fever, most prevalent under age 10 (Centers for Disease Control and Prevention, 2000b). Some arboviruses, which are transmitted by different species of mosquitoes, preferentially infect the young (e.g., La Crosse encephalitis carried by a woodland mosquito; Centers for Disease Control and Prevention, 1990a, 1998a). Cat scratch disease, carried by cats, has an estimated annual incidence of 22,000 cases, with the highest age-specific incidence in children less than age 10. Up to 25 percent of these cases result in severe systemic illness (Centers for Disease Control and Prevention, 2002a).
Few studies have estimated children’s exposure to noise or the effect of noise on children’s health, but there is suggestive evidence of its effect. Children appear to be routinely exposed to more noise than the recommended upper limit proposed by the U.S. Environmental Protection Agency in 1974 (De Joy, 1983; Roche et al., 1982). Noise-induced hearing loss in one or both ears among children ages 6 to 19 was found to be 12.5 percent (or 5.2 million children) (Niskar et al., 2001) and more frequent among high school students actively involved in farm work compared with peers not involved (Broste et al., 1989). In a sample of 1,218 children, 1 in 20 school-age children had minimal sensorineural hearing loss and 37 percent of the children with this hearing loss failed at least one grade (K–12) (Bess et al., 1998). Even mild hearing loss is associated with increased social and emotional dysfunction among school-age children.
Noise exposure in childhood is associated with a stress response (Tafalla and Evans, 1997—in male college students), headaches (Odegaard et al., 2003), sleep deprivation (Corser, 1996; Cureton-Lane and Fontaine, 1997), elevated blood pressure and heart rate (Matheson et al., 2003; Evans et al., 2001; Regecova and Kellerova, 1995), and poor performance including reading comprehension and long-term memory (Matheson et al., 2003; Stansfeld et al., 2000).
Exposure to ultraviolet B radiation from sunlight exposure and the use of tanning equipment during childhood can result in substantial morbidity and mortality later in life. Health risks from exposure vary with skin type and include sunburn, skin cancer (the most common malignant neoplasm in the U.S. adult population), phototoxicity and photoallergy, skin aging, and cataracts. Approximately 80 percent of lifetime sun exposure occurs before the age of 18. Episodic high exposures sufficient to cause sunburn, particularly during childhood and adolescence, increase the risk of melanoma (Saraiya et al., 2003).
Ionizing radiation comes from both natural and manmade sources. Natural sources include radon, cosmic radiation, and ingested radon and fallout. Manmade sources include medical X-rays and some consumer products. The consequences of exposure for children’s health include birth defects from prenatal exposures (microcephaly, mental retardation), neurological damage in younger children, and cancer (American Academy of Pediatrics, 1998).
Home, School, and Work Settings
The quality of their housing influences children’s health. Housing conditions can contribute to the incidence of asthma, injuries, and lead poisoning (Manuel, 1999). As children age, they spend more time in physical locations outside the home, such as child care, school, and workplace settings that expose them to new physical environments. Thus, parents’ choice of child care facility may affect both indoor and outdoor (e.g., playgrounds, backyards) exposures. For example, child care exposure to cigarette smoke may differ from exposure in children’s own homes (Wright et al., 1989).
School-age children spend 35 to 50 hours per week in and around school buildings. In some communities, schools have been built on relatively undesirable land, such as landfill sites like Love Canal. Schools are often located on old industrial sites or near highways, resulting in exposure to auto emissions and air pollution (Frumkin, 2003). Many school buildings are old and poorly maintained, leading to exposures to air pollutants, radon, asbestos, pesticides, and lead (Etzel and Balk, 1999). The U.S. General Accounting Office reported that 20 percent of primary and secondary schools had indoor air quality problems; more than half had environmental pollutant or building ventilation problems that could affect air quality (U.S. General Accounting Office, 1995). Radon above the EPA’s action level was found in 2.7 percent of schools surveyed during the 1990–1991 school year (U.S. Environmental Protection Agency, 1992). Asbestos, used extensively in schools until the 1970s, was still present in more than 8,500 schools in 1980, potentially exposing over 3 million students (U.S. Environmental Protection Agency, 1987).
Many adolescents have jobs that may expose them to occupational hazards (Pollack et al., 1990). Every year, at least 70 children die from work-related incidents (Centers for Disease Control and Prevention, 1996) and more than 65,000 are injured severely enough to seek care in emergency departments (Brooks et al., 1993). Under the Fair Labor Standards Act of 1938, which regulates work hours and safety, children younger than 18 are prohibited from working with hazardous chemicals in nonagricultural jobs. Prohibitions on chemical work in agriculture extend only to age 16, and work by children and adolescents on their own family farms is unregulated at the national level. During 1992–1995, 155 deaths were reported among agricultural workers age 19 and younger; 64 (41 percent) of these youths were working in their family’s business (Derstine, 1996). For each death, many more experience nonfatal injury (Rivara and Barber, 1985), usually from farm machinery or exposure to toxins.
Child Injury and the Provision of Safe Environments
Injuries are the leading cause of death among children between ages 1 and 19, accounting for more deaths than homicide, suicide, congenital anomalies, cancer, heart disease, respiratory illness, and HIV combined (Centers for Disease Control, 10 leading causes of death, 1997). Although the total number of unintentional injury deaths has declined by more than 40 percent during the past 20 years (CDC Injury Mortality Stats), the rates of childhood injury are much higher in the United States when compared with other developed countries. In 2001, unintentional injuries consttuted 70 percent of all injury deaths to children and adolescents (0 to 20 years) in the United States (National Center for Health Statistics, 2004).
The enormous impact of injury on children’s health is manifest by the fact that approximately 18 hospitalizations and 233 emergency department visits occur for every injury death (Grossman, 2000). As injury deaths continue to decline, nonfatal injuries continue to be important causes of child morbidity and disability and substantially reduce quality of life, especially among adolescents. However, it should be noted that data collection on nonfatal injuries is incomplete.
The elements of a safe and healthy physical environment differ according to a child’s developmental stage. The American Academy of Pediatrics has conducted extensive reviews of the literature to establish the evidence-based recommendations in The Injury Prevention Program, an age-appropriate prevention education program (www.aap.org/family.tipmain.org/) for physicians and families. Recommendations include counseling parents on use of infant car seats, never leaving infants and toddlers alone in pools or bathtubs, the use of safety equipment for in-line skating and skateboarding, and firearm safety.