A Trajectory Analysis of Alcohol and Marijuana Use Among Latino Adolescents in San Francisco, California

Purpose: We examined alcohol and marijuana use trajectories among Latino adolescents in the San Francisco Bay Area. Methods: A total of 410 Latino adolescents aged 14-19 years were recruited from community venues from years 2001 to 2004 and followed up for 2 years. In separate models, we identified groups with similar temporal patterns of alcohol and marijuana use using semi-parametric latent group trajectory modeling. Multivariable multinomial logistic regression was used to identify factors associated with the probability of trajectory group membership. Results: The use of alcohol (76%) and marijuana (55%) in the previous 6 months was common. Three alcohol-use trajectories were identified: low users (18%), moderate users (37%), and frequent users (45%). Low alcohol users (vs. moderate users) were found to be younger in age, preferred Spanish language, and had more parental monitoring. Frequent users were more likely to be male, sexually active, gang exposed, and have less parental monitoring than moderate users. Similarly, three marijuana-use trajectories were identified: low users (36%), moderate users (35%), and frequent users (28%), with similar correlates of group membership. Conclusions: Urban Latino adolescents' substance use is shaped by complex cultural and environmental influences. Patterns of substance use emerge by early adolescence highlighting the need for timely intervention. (C) 2010 Society for Adolescent Health and Medicine. All rights reserved.