Differential Determinants of Young Adult Substance Use and High‐Risk Sexual Behavior¹

This investigation evaluated how personality traits, self‐efficacy, and outcome expectancies differentially relate to young adult substance use and high‐risk sex. Experiments I ( N = 481) and 2 ( N = 73) report the development of a new questionnaire to assess self‐efficacy for substance use and sexual behavior. Experiment 3 ( N = 375) tested self‐efficacy, outcome expectancies, and trait measures of social conformity and sensation seeking as correlates of substance use and high‐risk sex. Using structural equation modeling, cross‐sectional analyses revealed that positive outcome expectancies had the largest association with substance use, whereas self‐efficacy had the largest association with sexual behavior. Further, personality traits were related to substance use and sexual behavior indirectly through outcome expectancies, with social conformity also having a direct effect on behavior. When examined longitudinally, past alcohol and drug use served as the final pathway by which expectancies and personality impacted substance use, whereas past behavior, self‐efficacy, and social conformity all contributed to high‐risk sex. Results support the utility of different models for explaining, and possibly preventing, young adult substance use and high‐risk sex.