Differentiating Common Predictors and Outcomes of Marijuana Initiation: A Retrospective Longitudinal Analysis.

This quasi-experimental secondary analysis, funded by NIDA, employed data from a national sample of 1,968 US adolescents, collected from 1999 to 2003, self-classified as resolutely anti-marijuana on the first two yearly assessments (T1 and 2). At T3, respondents remained resolute non-users, or had moved to vulnerable non-use or use. Analysis of variance indicated that users at T3 were significantly heavier users of tobacco and alcohol, and reported significantly less intense parental monitoring, than those who did not initiate marijuana use. Furthermore, categorizing non-users as either resolute or vulnerable revealed behavioral patterns that otherwise would have been unidentified. Implications for prevention are discussed.