Substance use problems reported by college students: combined marijuana and alcohol use versus alcohol-only use.

This study examines the relationships among selected demographic characteristics, alcohol use only, alcohol plus marijuana use and substance-use related problems. Data are from 409 randomly selected undergraduate college students attending a large urban university. Poly-substance users were more likely than alcohol only users to be younger and experience all substance-use related problems studied. The relationship between poly-substance use and increased substance use-associated problems was also identified when controlling for other common predictors of substance use problems.