This chapter provides a review of the current knowledge linking childhood adversity to adult physical health. We first provide a discussion of childhood adversity and the varied ways that children encounter stressful experiences in their daily lives. Then we review evidence for links between childhood adversity and chronic diseases of aging, with a focus on cardiovascular disease and metabolic disorders, where most of the research to date has occurred. We then describe conceptual models that help guide empirical investigation of the processes through which early adversity influences later health. We also review biological mechanisms that might play an intermediary role in translating psychosocial stress into health problems, which can help explain how early adversity âgets under the skinâ and influences the onset of disease in adulthood. Our goal is to highlight the advantages and limitations in the conclusions we can draw from research on these biological processes. Finally, we end this chapter with a series of important research questions that should be a focus in the next generation of empirical investigation on early adversity and adult physical health.
Defining Childhood Adversity
There are a number of ways that children could experience significant adversity. In this chapter, we focus on adversity that is both chronic and severe in nature. We define chronic adversity as one that remains present in the child's life over a significant period of time (e.g., lack of material resources due to poverty). Adversity can also be chronic when children experience lingering threat over the possibility of a repeated stressful experience (e.g., stress resulting from a traumatic experience, such as abuse, that could reoccur) or aftereffects of adversities that create severe disruptions to daily life (e.g., long-term displacement resulting from a natural disaster). Adversity is considered severe when it results in a profound unsettling of normative childhood experiences and threatens the well-being of the child (e.g., exposure to gang violence while living in poverty).
Studies that have attempted to estimate the prevalence of adverse life experiences in childhood have found that these stressors actually are fairly common. Kessler and colleagues (Kessler, Davis, & Kendler, 1997) categorized early-life adversities into four domains, including (a) interpersonal traumas (e.g., rape, physical attacks); (b) loss events (e.g., death of a parent); (c) parental psychopathology (e.g., parental depression, antisocial personality disorder); and (d) a miscellaneous category of stressful life events (e.g., life-threatening accidents, man-made disasters). Using the National Comorbidity Survey, a nationally representative sample of families in the United States, Kessler et al. found that by the age of 16, nearly 75% of children have experienced at least one significant adversity and approximately 50% of children have experienced multiple adversities. In this sample, the most frequent adversities that children faced were maternal depression, paternal verbal abuse, paternal substance abuse, and parental separation or divorce.
Further, a startling number of children currently face adversity in impoverished or economically stressed conditions. According to the Children's Defense Fund (2012), 22% of children in the United States were living in poverty in 2010, meaning that a family of four earns less than $22,350 a year (U.S. Department of Health and Human Services, 2011). An additional 22% of children live in low-income families, defined as less than 200% of the federal poverty level (or less than $44,700 for a family of four). Children in low-income families may be exposed to many of the same stressors that children living below the poverty line face, including dangerous neighborhoods, material deprivation, parental underemployment, and familial mental health problems, all contributing to strained family relationships.
Overwhelmingly, research on the links between early adversity and later physical health has focused on two types of adversity: child maltreatment and socioeconomic disadvantage. Although these experiences of early adversity fall under the definition of adversity proposed above, they differ from each other in some critical aspects, including the nature and source of threatening experiences; the duration, frequency, and severity of those experiences; and the opportunities for coping. Yet maltreatment and socioeconomic disadvantage share several overlapping qualities, which may include cold, insensitive parenting; harsh discipline; exposure to conflict and violence; limited access to resources; and uncertainty of future environmental stability (Repetti et al., 2002). Next we take a closer look at several forms of adversity that are thought to be particularly detrimental for later physical health.
Child Maltreatment
A fundamental component of attachment theory is the notion that individuals develop representations (or internal working models) that reflect the extent to which a caregiver serves as a secure base for exploration and as a safe haven when needed for comfort and support (Bowlby, 1969/1982, 1973). These representations are experience-based, and they are developed over the first year of life in response to repeated interactions with a caregiver. When these caregiving experiences include neglect or abuse, children learn that their caregiver is not an available secure base or safe haven. Further, these children may develop unusual behaviors, characterized by odd, fearful, and disorganized patterns of interactions with a caregiverâcharacteristics that emerge when the caregiver becomes their primary source of fear and support (Lyons-Ruth & Jacobvitz, 2008). These behavioral responses reflect the child's inability to cope with a chaotic environment. Importantly, children who are maltreated by caregivers grow up without the experience of knowing that a reliable caregiver is available when neededâan aspect of the family emotional climate that plays a fundamental role in children's abilities to regulate distress and cope with negative emotions (Bowlby, 1988).
Child maltreatment is a serious public health concern that poses significant mental and physical health burdens on its victims (Cicchetti & Toth, 2005) as well as substantial economic burdens on society as a whole (Fang, Brown, Florence, & Mercy, 2012). Estimates suggest that almost 700,000 children were victimized in the United States in 2011, almost half of whom were under 6 years old at the time of the abuse (U.S. Dept. of Health and Human Services, 2011). Of course, because a large number of cases are unreported and a third of reported cases are not investigated (Cicchetti & Toth, 2005), the actual rate of child maltreatment may in fact be higher. The vast majority of cases (78%) included children suffering from neglect, but each year, hundreds of thousands of children are also victims of physical, sexual, or psychological abuse. Alarmingly, childhood maltreatment is perpetrated most often by primary caregivers, with over 80% of cases involving abuse by one or more parents.
Explanations for the causes of child maltreatment widely recognize that the phenomenon is multiply determined. Attempts to characterize the contexts of maltreatment have cited parental factors (e.g., mental illness, substance abuse), child factors (e.g., difficult temperament, disruptive behavior), interactional factorsâthat is, the dynamic transactions that take place between parents and children that might incite abuse (e.g., a child's aggressive behavior elicits physical punishment from parents that subsequently escalates to abuse), and environmental factors (e.g., cultural attitudes, poverty; Belsky, 1993; Cicchetti & Toth, 2005).
Socioeconomic Disadvantage
Children growing up with socioeconomic disadvantage have a higher probability of being exposed to stressful conditions across virtually every domain of daily life. Many of these stressful conditions center on the lack of security for basic resources, such as food and housing. For example, over 10% of children live in âfood-insecureâ families who struggle to provide enough food to meet children's daily nutritional needs, and over 20 million children receive free or reduced-cost lunches at schoolâmeals they are eligible to receive because of their family's scarce financial resources (Children's Defense Fund, 2012). Children in poverty often do not have adequate access to medical care, resulting in infrequent visits to the doctor and risk for serious complications from untreated illnesses. Children growing up in poverty are at risk for low educational attainment, meager job success, and incarceration (Duncan, Kalil, & Ziol-Guest, 2008). Notably, children in poverty also face neighborhood stressors, and they are at increased risk for becoming victims of violence, theft, and other crimes (Ross & Mirowsky, 2001). Further, their caregivers are burdened by numerous demands, such as multiple part-time jobs, unaccommodating schedules, and psychosocial stress brought on by their lack of resources, making it more difficult for them...
