Effects of Cannabis Abstinence on Symptoms and Cognition in Major Depressive Disorder

Individuals with major depressive disorder (MDD) exhibit high rates of cannabis use and research has indicated that cannabis use leads to increased risk for depression and suicidal behavior. This study sought to examine the effects of cannabis abstinence on symptoms of depression in cannabis users with MDD. Participants (n=11) underwent 28 days of cannabis abstinence. Mood symptoms were assessed weekly and cognitive symptoms bi-weekly. Abstinence was biochemically verified using weekly urine assays and participants were rewarded with a $300 contingent bonus if abstinence was confirmed. 72.7% of study completers achieved abstinence. Participants exhibited significant improvements in depressive symptoms (43.7% reduction from baseline), especially anhedonia (88.7% reduction from baseline). Improvements in visuospatial working memory performance were significant. These findings suggest ceasing cannabis use leads to reductions in depressive symptoms, and selective improvements in cognition. This research has important implications for the treatment of problematic cannabis use in individuals with MDD.M.Sc