Depressive Symptoms and Substance Use: Longitudinal Examination of Alcohol and Cannabis Coping Mechanisms in Young Adults.

Depression and substance use are often comorbid, but less is known about these associations in non-clinical community samples. Moreover, existing research is primarily cross-sectional or focuses on long-term trajectories of depressive symptoms and substance use. The present study examines within-person associations to estimate the extent to which monthly fluctuations in depressive symptoms relate to alcohol and cannabis use. A community sample of 778 young adults (M_age = 21.1 at baseline, 56% female) completed up to 33 monthly surveys (82.7% total response rate) scattered across a 6-year period (2015-2021). Zero-truncated regression was used to stratify associations with any use and amount of use on months that alcohol and cannabis were reported, respectively. Pertaining to alcohol use, depressive symptoms predicted lower odds of drinking alcohol on a given month; however, if young adults did drink, then depressive symptoms predicted heavier drinking (i.e., more drinks per week). For cannabis, depressive symptoms predicted both greater odds of using cannabis and heavier use in that month (i.e., greater hours high per week). Associations between depressive symptoms and alcohol/cannabis quantity indices were mediated by coping motives. Findings highlight the risks of elevated depressive symptoms for young adults, in terms of alcohol and cannabis use.