LONGITUDINAL PROSPECTIVE RELATIONS BETWEEN CANNABIS USE AND SUBSTANCE-FREE ACTIVITIES IN A DIVERSE COMMUNITY SAMPLE OF EMERGING ADULT HEAVY DRINKERS

National drinking and drug use trends suggest emerging adulthood (ages 18-25) is the developmental apex of harmful co-use of alcohol and drugs, with notable recent increases in cannabis use among emerging adults. Many emerging adults naturally begin to reduce harmful alcohol or drug use into their late 20s and 30s, however, a significant subgroup report a developmentally persistent pattern of frequent alcohol and cannabis use. There is evidence that limited access to alternative substance-free reinforcement (SFR) is a risk factor for chronic alcohol and drug misuse, there is a need for longitudinal research that examines changes in patterns of SFR and cannabis use during this developmental window. This study examined baseline associations and dynamic relations between cannabis use and SFR using latent change score modeling over 32-months (five assessment waves) in a community sample of heavy drinking emerging adults (baseline N = 439, Mage = 22.60, 53.8% female, 47.7% White, 41.3% Black). Cannabis use and depressive symptoms were associated with less access to substance-free rewards at baseline. Participants with less household income, other drug use in the past-month, and more recent heavy drinking days reported more cannabis use at baseline. Cannabis use and SFR showed small decreases over study waves and participants with higher baseline cannabis use showed smaller reductions in cannabis use over time and steeper reductions in SFR. Assigned sex and college status influenced the magnitude of change trajectories of SFR (Female: β = -.09, p = .02 Male: β = -.23, p \u3c .001) and cannabis use (Non college: β = -.12, p \u3c.001; College: β = -.22, p \u3c .001), respectively. Contrary to hypotheses, cannabis use was not prospectively associated with subsequent change in substance-free activity engagement across waves, or vice versa. Overall results are consistent with previous research suggesting that cannabis use is associated with less access to SFR, but do not suggest a specific prospective association between these two outcomes in emerging adult heavy drinkers