Abstract
This pilot study sought to test the feasibility of procedures to screen students for marijuana use in Student Health Services (SHS) and test the efficacy of a web-based intervention designed to reduce marijuana use and consequences. Students were asked to participate in voluntary screening of health behaviors upon arrival at SHS. One hundred and twenty-three students who used marijuana at least monthly completed assessments and were randomized to one of four intervention conditions in a 2 (intervention: Marijuana eCHECKUP TO GO vs. control)×2 (site of intervention: on-site vs. off-site) between-groups design. Follow-up assessments were conducted online at 3 and 6 months. Latent growth modeling was used to provide effect size estimates for the influence of intervention on outcomes. One thousand and eighty undergraduate students completed screening. The intervention did not influence marijuana use frequency. However, there was evidence of a small overall intervention effect on marijuana-related consequences and a medium effect in stratified analyses in the on-site condition. Analyses of psychological variables showed that the intervention significantly reduced perceived norms regarding peer marijuana use. These findings demonstrate that it is feasible to identify marijuana users in SHS and deliver an automated web-based intervention to these students in different contexts. Effect size estimates suggest that the intervention has some promise as a means of correcting misperceptions of marijuana use norms and reducing marijuana-related consequences. Future work should test the efficacy of this intervention in a full scale randomized controlled trial.