Extending the theory of planned behavior to predict alcohol, tobacco, and marijuana use among youth of Mexican heritage.

This study examined the applicability of extending the theory of planned behavior to explain the normative processes in substance use among Mexican-heritage youth. The theory identifies norms, attitudes, and perceived behavioral control as predictors of intentions, which in turn, predict behaviors. To date, the theory had a limited conceptualization of norms and had not been extended to youth of Mexican descent, one of the fastest growing segments of the U.S. population and one at particular risk for alcohol, tobacco, and marijuana use. Based on norm focus theory, it was hypothesized that norms are multidimensional, consisting of parental injunctive, peer injunctive, descriptive, and personal substance use norms. Second, it was hypothesized that parental injunctive, peer injunctive, and descriptive norms indirectly affect substance use intentions through attitudes, personal norms, and perceived behavioral control. The third hypothesis postulated that the model would operate differently based on Mexican-heritage youths' country of origin. Mexican-heritage youth (N = 1,499) from 30 elementary schools in Phoenix, AZ completed questionnaires in three waves over 18 months as part of a larger study. The findings supported the first hypothesis, showing the multidimensionality of norms. The second hypothesis was partially supported by findings from a multi-group multilevel path analysis using Mplus. Descriptive norms' association with intentions was partially mediated by attitudes, personal norms, and perceived behavioral control, while parental and peer injunctive norms were fully mediated, partially supporting the second hypothesis. Contrary to the third hypothesis, the mediation model did not differ based on Mexican-heritage youths' country of origin.