Those with early substance use onset are more likely to continue use into adulthood; individuals who first used alcohol at age 14 or younger have a >5 time increased risk of lifetime alcohol use disorder as compared to those who first used alcohol after the U.S. legal limit of the 21st birthday (SAMSHA 2009). Adolescent alcohol and marijuana use has been linked to harmful effects on physiological, social, and psychological functioning (Macleod et al. 2004; Tucker et al. 2006a, b). This includes increased delinquency (Nation and Heflinger 2006; Shoal et al. 2007), aggressivity, risky sexual behaviors, hazardous driving, and comorbid substance use (Neal and Fromme 2007).
