Consumption of cannabis continues to climb throughout the United States, and college-aged adults are a particular population displaying some of the sharpest increases in the current trend.  Even though cannabis purchase and consumption is legal in a growing number of states, its use has been associated with deleterious effects on the health and well-being of university students.  The inclination to use cannabis has been found to have a significant genetic component, and it is important to investigate the factors that moderate biological predispositions in order to design interventions to deter students from use.  The purpose of this study was to test the influence of polygenetic markers, social activity participation, and peer deviance on cannabis use outcomes, and how they relate to genetic predispositions of use.  

The study sample was composed of volunteer students from a large mid-Atlantic university who provided yearly, longitudinal data from 2011 to 2014.  The two sample cohorts were divided based upon European Ancestry (EA, N=750) or African American ancestry (AA, N=405) in order to account for genetic population stratification when examining genetic variables.  Students were asked to report whether or not they used cannabis during their first year in school, as well as in the past 12 months.  Students supplied saliva-based DNA samples which were genotyped and assigned polygenic risk scores (PRS) as their samples were compared to that of established genome wide association study samples (GWAS) for individuals of EA or AA, depending upon their cohort.  Lastly, students reported their exposure to peer deviance in the past year (friends who smoked cannabis, etc.), as well as their involvement in a number of different organized community activities (intramural/scholarship athletics, church, volunteering, etc.).  Data was analyzed using logit link function and AR1 working correlation structures. 

Results of the study found that never engaging in community activities moderated the effects of PRS on likelihood of using cannabis (meaning genetically predisposed individuals will be increasingly likely to use cannabis if they do not engage in these activities).  Peer deviance in both cohorts was found to be a reliable predictor of cannabis usage, while PRS alone was not found to have a salient effect on usage rates in either cohort.  Amongst all activities mentioned in the study, engagement in church activities was found to have the only significantly lower association with cannabis use reporting.   

Takeaway: probabilities of using cannabis can be estimated using a number of different genetic, social, and behavioral variables, and the research uncovering their specifics continues to develop though it still exists in nascent stages.  This study emphasized the importance of college students engaging in organized community activities in order to mitigate/eliminate cannabis use risk factors as well as the impact that peer groups exhibit on usage. 

Thomas NS, Salvatore JE, Gillespie NA, Aliev F, Ksinan AJ, Dick DM. Cannabis use in college: Genetic predispositions, peers, and activity participation. Drug and Alcohol Dependence. 2021;219:108489. doi:10.1016/j.drugalcdep.2020.108489