Increased use of marijuana and other illicit drugs at US colleges in the 1990s: results of three national surveys

Aims. To examine rates and patterns of marijuana and other illicit drug use among different types of students and colleges in 1999, and changes in use since 1993. Design. Self-administered mail survey (Harvard School of Publi c Health College Alcohol Study). Setting. One hundred and nineteen national ly representative US 4-year colleges. Participants. A representative sample of 15 403 randomly selected students in 1993, 14 724 students in 1997 and 14 138 students in 1999. Measurements. Self-reports of marijuana and other illicit drug use in the past 30 days and in the past year, cigarette use, d rinking behavior, and age of initiation of smoking, drinking and using mari juana. Findings. The prevalence of past 30-day marijuana use rose from 12.9 % to 15.7% between 1993 and 1999, an increase of 22%. Almost all of this ch ange occurred by 1997. An increase was observed at 66% of the 119 colleges. The prevalence of 30-day and annual marijuana use increased in nearly all student demographic subgroups except for Hispanic students, and at all type s of colleges except for colleges with low binge drinking rates. Rates of i llicit drug use in the past 30 days increased slightly for other illicit dr ugs in the 4-year interval except for LSD. Nine out of 10 students (91%) wh o used marijuana in the past 30 days used other illicit drugs, smoked cigar ettes and/or engaged in binge drinking. Of students who used any other illi cit drug in the past 30 days, 87% used another substance or binge drank. Tw enty nine per cent of past 30-day marijuana users first used marijuana and 34% began to use marijuana regularly at or after the age of 18, when most w ere in college. Conclusions. Use of marijuana and other illicit drugs has i ncreased on campuses across the United States in most student subgroups and all types of colleges. This may re? ect earlier increases in middle school s and secondary schools among this cohort. However, nearly one-third of stu dents initiated marijuana use in college and one of three began to use it r egularly. Intervention efforts should be directed at college students, as w ell as secondary school students.