The study found that the youth who were most prone to receive intrinsic gratification from high-risk and thrill-seeking behaviors were significantly more likely than their counterparts to engage in each of the substance use activities. This finding suggests that nonsocial reinforcement is the strongest theoretical predictor of substance use among incarcerated youth, regardless of the substance (alcohol, hard drugs, or soft drugs). This theory holds that some individuals may receive an internal (or nonsocial) reward or reinforcement from committing a delinquent act. These types of reinforcements result from internal gratifications rather than external ones, such as gaining approval and status among peers. The fact that most of the youths received internal gratification from their substance use makes two potentially addictive factors work together to encourage continued substance use: the neurophysiological high received from the body's chemicals as the youth engages in risky behavior and the pharmaceutical high caused by the drug itself. The second strongest theoretical predictor in the study is social learning theory. Respondents' delinquent peers had a strong influence on the youths' involvement in substance use. The third strongest theoretical predictor is social bond theory, which holds that delinquent behaviors stem from a lack of exposure or commitment to bonding with role models for normative behavior. The least relevant of the theoretical predictors is strain theory, since these youth had given up on pursuing normative socioeconomic goals. Implications are dawn for drug prevention programs for youth. 6 tables and 55 references