This study adapted and extended M. L. Cooper's (1994) Drinking Motives Measure to examine marijuana motives among 299 college students. An exploratory factor analysis supported the hypothesized 5-factor marijuana motives model, resulting in enhancement, conformity, expansion, coping, and social motives. Analyses supported the internal consistency and concurrent validity of the 5 marijuana motives. Marijuana motives were significant predictors of marijuana use and added to the prediction of use-related problems above and beyond the contribution of lifetime use. Motives and gender interacted in predicting use and use-related problems. Parallel regression analyses revealed that marijuana and alcohol motives predicted comparable amounts of variance in use and use-related problems. However, different patterns of relations emerged across drugs, supporting the discriminant validity of the marijuana and alcohol motives.

The study examined models of marijuana (n = 309) and alcohol (n = 731) problems. Impulsivity was directly associated with both marijuana- and alcohol-related problems. Negative mood regulation expectancies were indirectly associated with marijuana problems through coping motives. Sensation seeking was indirectly associated with alcohol problems through enhancement motives. Affect lability and negative affect were indirectly associated with alcohol problems though coping motives. In both models, coping motives were directly associated with use-related problems. A multigroup analysis indicated that the association between negative affect and coping motives as well as use and problems was stronger among participants using both alcohol and marijuana relative to alcohol only. Enhancement motives were a stronger predictor of alcohol use among participants using alcohol only.

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Behavioral theories of choice predict that substance use is partly a function of the relative value of drugs in relation to other available reinforcers. This study evaluated this hypothesis in the context of predicting drinking outcomes following an alcohol abuse intervention. Participants (N ϭ 54, 69% female, 31% male) were college student heavy drinkers who completed a single-session motivational intervention. Students completed a baseline measure of substance-related and substance-free activity participation and enjoyment. Only women showed a significant reduction in drinking at the 6-month follow-up, and the ratio of substance-related to substance-free reinforcement accounted for unique variance in their drinking outcomes. Women who at baseline derived a smaller proportion of their total reinforcement from substance use showed lower levels of follow-up drinking, even after the authors controlled for baseline drinking level. Male and female participants who reduced their drinking showed increased proportional reinforcement from substance-free activities.

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