Within-person and between-person associations of access to environmental reward with alcohol and cannabis use and consequences among young adults

Background: Recent behavioural economic models of substance use suggest that low access to environmental reward may increase risk for heavy substance use and associated harms. Most prior studies of these associations have been cross-sectional and have focused on alcohol. The current study extends this research using longitudinal data to examine the within-person and between-person associations of environmental reward access with both alcohol and cannabis outcomes. Method: Young adults (N N = 119, 64.71 % female) completed an online survey at three time points, spaced six months apart. The survey included measures of alcohol and cannabis use and consequences, and two facets of environmental reward access: reward probability (i.e., likelihood of experiencing environmental reward) and environmental suppression (i.e., diminished availability of environmental reward). Results: Multilevel models revealed that at the between-person level (i.e., averaged across time points), greater environmental suppression (but not reward probability) was significantly associated with more frequent cannabis use, and greater reward probability (but not environmental suppression) was significantly associated with heavier alcohol use. Higher environmental suppression (but not reward probability) was also associated with greater alcohol and cannabis consequences at the between-person level, over and above level of use. A significant within-person association also was observed, wherein participants reported relative increases in cannabis consequences during time periods when they also reported relative decreases in the availability of environmental reward. Conclusions: Results highlight environmental suppression as a risk factor for more frequent cannabis use and for both alcohol and cannabis consequences, and provide novel support for a within-person association between environmental suppression and cannabis consequences over time. Findings may inform contextual interventions for young adult substance use.