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 Public Health College Alcohol Study).
Setting: One hundred and nineteen nationally 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, drinking behavior, and age of initiation of smoking, drinking and using marijuana.
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 change 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 types of colleges except for colleges with low binge drinking rates. Rates of illicit drug use in the past 30 days increased slightly for other illicit drugs in the 4-year interval except for LSD. Nine out of 10 students (91%) who used marijuana in the past 30 days used other illicit drugs, smoked cigarettes and/or engaged in binge drinking. Of students who used any other illicit drug in the past 30 days, 87% used another substance or binge drank. Twenty 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 were in college.
Conclusions: Use of marijuana and other illicit drugs has increased on campuses across the United States in most student subgroups and all types of colleges. This may reflect earlier increases in middle schools and secondary schools among this cohort. However, nearly one-third of students initiated marijuana use in college and one of three began to use it regularly. Intervention efforts should be directed at college students, as well as secondary school students.