• Adolescents who enter the juvenile justice system generally have preexisting health problems, particularly substance abuse, sexually transmitted infections, unplanned pregnancies, dental problems, and psychiatric disorders.

• Adolescents in foster care face more health challenges and chronic health issues—such as asthma, anemia, neurological abnormalities, emotional and behavioral problems, chronic physical disabilities, birth defects, and developmental delays—than those not in foster care. These adolescents are also at increased risk of unprotected sex and pregnancy, and have higher rates of severe mental health problems and substance use.

Most adolescents are considered healthy as defined by the traditional medical measures of health status, such as mortality rates, incidence of disease, prevalence of chronic conditions, and use of health services. According to the National Survey of Child Health, approximately 83 percent of adolescents aged 12–17 are in either excellent or very good health as reported by their parents, regardless of whether they live in urban or rural areas (Maternal and Child Health Bureau, 2005a,b). According to data from the Behavioral Risk Factor Surveillance System, 91 percent of those aged 18–24 consider themselves to be in good, very good, or excellent health (McCracken, Jiles, and Michels Blanck, 2007).

This chapter explores how timing matters—how adolescence is a critical time for health promotion. Many adolescents behave in risky ways or live in environments that not only affect their immediate health, but also have a significant impact on their health as adults. For example, McGinnis and Foege (1993) and more recently Mokdad and colleagues (2004) have shown that half of deaths among adults are due to health-related behaviors that for many people have their onset during adolescence. For example, tobacco use is the leading actual cause of preventable death in the United States. Other health-related behaviors that are associated with the leading causes of death include poor diet and physical inactivity, drug and alcohol abuse, risky driving, risky sexual behavior, and use of drugs. The effects of such health-compromising behaviors—and the extent to which the health system attempts to prevent and respond to them—are also influenced by socioeconomic status, living circumstances, school environment and quality, and after-school care. This chapter also considers how context matters for adolescents and their health and looks at how the social context and such factors as income, race/ethnicity, geography, and community efficacy may affect the health of adolescents. (The importance of context in adolescents’