and salty snacks—consistently dominate (Institute of Medicine, 2006). Once they reach age 18, adolescents also may be purchasing health care independently, with additional potential impacts on health.

Research conducted in the last decade suggests that the brain is not completely developed until late in adolescence, and until that time, the connections between neurons affecting emotional, physical, and mental abilities are incomplete. Some adolescent behavior, such as inconsistency in controlling emotions, impulses, and judgments, may be attributable to this incomplete brain development, and much of that behavior is associated with unhealthful and risky adolescent activities (Dahl, 2003; Giedd et al., 1999; National Institute of Mental Health, 2001).

The committee recognized that among health care providers, researchers, and policy makers, different age brackets often demarcate the period of adolescence, ranging from as young as 10 to as old as 25. In most cases, those at the upper end of this age range are identified separately as “young adults” or “emerging adults.” Even within the U.S. government, several definitions are in use. Examples include the following:

  • U.S. Department of Health and Human Services (2007) (Healthy People 2010)

    • Adolescents (ages 10–19)

    • Young adults (ages 20–24)

  • Substance Abuse and Mental Health Services Administration (2007) (National Survey on Drug Use and Health)

    • Youths (ages 12–17)

    • Young adults (ages 18–25)

  • Centers for Disease Control and Prevention (2006) (STD Surveillance)

    • Adolescents (ages 10–19)

    • Young adults (ages 20–24)

  • U.S. Department of Justice (2006) (Criminal Victimization)

    • Age clustering: ages 12–15, 16–19, 20–24

  • Youth Risk Behavior Survey (Centers for Disease Control and Prevention, 2007)

    • Young people (grades 9–12)

  • Society for Adolescent Medicine (1995) (position statement)

    • Adolescent medicine (ages 10–25)

  • National Longitudinal Study of Adolescent Health (Carolina Population Center, 2007)

    • Adolescents (grades 7–12)

  • Office of Technology Assessment (OTA) (U.S. Congress and Office of Technology Assessment, 1991)

    • Adolescents (ages 10–18)

    • Young adults (ages 18–26)

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