Effects of a Parent-Based Intervention on Positive and Negative Alcohol and Cannabis Consequences Among First Year College Students

College student alcohol and cannabis use is associated with negative and positive consequences, the latter of which is associated with greater subsequent use. This study tested a parent-based handbook intervention on first-year students’ alcohol and cannabis consequences. Parent-student dyads were randomized to control ( n = 309) or handbook ( n = 609). Parents received the handbook before college. Students completed surveys in their senior year of high school (baseline) and first semester of college (time 2). Zero-inflated Poisson regression models examined intervention effects on negative and positive alcohol and cannabis consequences at time 2 and potential gender moderation. Compared to controls, intervention students were more likely to report zero negative and positive alcohol and cannabis consequences, fewer negative and positive cannabis consequences, and fewer positive alcohol consequences, with some associations more pronounced for males compared to females. Findings suggest this low-cost handbook is an effective strategy to reduce alcohol- and cannabis-related harms among college students.