Young Adult Use, Dual Use, and Simultaneous Use of Alcohol and Marijuana: An Examination of Differences Across Use Status on Marijuana Use Context, Rates, and Consequences

Co-use of alcohol and marijuana has increased among college students, though comparisons among simultaneous (i.e., use of both substances such that effects overlap), dual (i.e., use of both substances within a similar time period but without overlapping effects), and marijuana-only use are limited. This study aimed to understand differences between simultaneous, dual, and marijuana-only users on marijuana use rates, consequences, and context of use in a multi-university study. Method: College students (N = 4,764; M-age = 19.9 years) who were mainly female (70.6%) and White (67.9%) completed an online survey. The Marijuana Use Grid captured marijuana use quantity/frequency, and the Brief Marijuana Consequences Questionnaire and the Cannabis Use Disorders Identification Test-Revised assessed problem use. Location, method of consumption, and social context of use also were assessed. Results: Fifty-five percent of the sample endorsed lifetime use of alcohol and marijuana. Of these students, 36.1% endorsed past-month simultaneous use, 10.8% endorsed past-month dual use, and 6.4% endorsed past-month marijuana-only use. Simultaneous users reported more marijuana use and problems than dual users. Marijuana-only users did not differ from simultaneous users on marijuana use indices, though they reported greater use than dual users as well. Simultaneous users used marijuana in plant form, at parties, and with unknown others a greater percentage of the time than dual users, while dual users used edibles and ingested marijuana a greater percentage of the time. Conclusions: Given their greater levels of marijuana use and marijuana-related problems, screening and interventions for simultaneous alcohol-marijuana use are needed in college students.