Contents lists available at ScienceDirect Drug and Alcohol Dependence journal homepage: www.elsevier.com/locate/drugalcdep Full length article Marijuana eCHECKUPTO GO: Effects of a personalized feedback plus protective behavioral strategies intervention for heavy marijuana-using college students Nathaniel R. Riggs a, ⁎ , Bradley T. Conner b , Jamie E. Parnes b , Mark A. Prince b , Audrey M. Shillington c , Melissa W. George a a Department of Human Development and Family Studies, Colorado State University, Fort Collins, CO, 80525, USA b Department of Psychology, Colorado State University, Fort Collins, CO, 80523, USA c School of Social Work, Colorado State University, Fort Collins, CO, 80523, USA ARTICLE INFO Keywords: Marijuana Intervention College students Personalized feedback Protective behavioral strategies On-line ABSTRACT Background: Marijuana use is common among U.S. college students. Liberalization of marijuana use policies is hypothesized to decrease social norms discouraging use, which protects against marijuana use. This may in- crease the importance of protective behavioral strategies (PBS) to reduce marijuana use harm. Methods: This study tested direct and moderated (by sex) program effects of an adapted version of the Marijuana eCHECKUPTO GO, a web-based marijuana use intervention providing university-specific personalized feedback (PF) with normative information and PBS to students attending a university in a state with legalized adult recreational marijuana. Participants were 298 heavy-using college students randomly assigned to receive Marijuana eCHECKUPTO GO or strategies for healthy stress management (HSM). General linear models (GLMs) tested direct program effects on proximal intervention targets, marijuana use, and use consequences. Multi- group GLMs then tested the moderating effect of sex on direct intervention effects. Results: Marijuana eCHECKUPTO GO participants reported decreases in estimated use prevalence (i.e., de- scriptive norms), self-reported hours high per week, days high per week, periods high per week, and weeks high per month. Sex moderated intervention effects on the use of PBS such that females in the PF condition increased their use of PBS more than males. Conclusion: Results demonstrate preliminary support for the adapted Marijuana eCHECKUPTO GO in reducing marijuana use for “heavy college-aged users”. Future research should test adapted Marijuana eCHECKUPTO GO sustained effects over time, and examine whether program effects on harm reduction manifest after sustained (e.g., booster) program implementation. 1. Introduction Marijuana use is common among U.S. college students with 22% percent reporting past-month use and daily use at its highest level in three decades (Schulenberg et al., 2017). Marijuana use is associated with several psychosocial and academic problems during college. Col- lege student marijuana users report more emotional problems including anxiety and depression, greater health service utilization for physical and mental health problems, and lower subjective well-being than non- users (Arria et al., 2016; Keith et al., 2015). Marijuana use during college has also been shown to be significantly associated with lower GPA, discontinuous enrollment, delay of graduation, and drop-out (Arria et al., 2013; Suerken et al., 2016). Thus, college student marijuana use represents a challenge to stakeholders from public health, mental health, and higher education sectors. 1.1. Perceived social norms and marijuana use prevention Perceptions of social norms encouraging use have been identified as risk factors for one’s personal marijuana use and misuse (Kilmer et al., 2007; Neighbors et al., 2008). Studies demonstrate positive associations between injunctive norms (i.e., perceptions of approval of use) and college student marijuana use. Specifically, perceptions of typical-stu- dents’ and close friends’ approval are positively associated with per- sonal use, and that perceptions of parents’ approval are indirectly as- sociated with personal use through personal approval of use (Labrie https://doi.org/10.1016/j.drugalcdep.2018.05.020 Received 23 October 2017; Received in revised form 25 April 2018; Accepted 21 May 2018 ⁎ Corresponding author. E-mail address: nathaniel.riggs@colostate.edu (N.R. Riggs). Drug and Alcohol Dependence 190 (2018) 13–19 Available online 23 June 2018 0376-8716/ © 2018 Elsevier B.V. All rights reserved. T