Grant: Doctoral Research Award: Canada Graduate Scholarships

Depression causes significant burden on society and is a major health issue. Substance use, including the use of cannabis commonly co-occurs with depression and may be contributing to this burden. Indeed, some research suggests that compared to depressed individuals who do not use cannabis, depressed individuals who regularly use cannabis tend to report greater depressive symptoms and are less likely to improve during treatment; however, it is not yet clear how cannabis works to worsen depression in these individuals. Those who are depressed tend to experience greater emotional reactivity to stressors (i.e., react more negatively) and also tend to experience reduced reward function (i.e., decreased motivation to pursue rewards and decreased reward learning), which contribute to maintaining depressive symptoms. To better understand the role of cannabis on these two processes, we will explore whether the regular use of cannabis in depression is associated with greater dysfunctional reactivity to stress and greater impairment in reward function compared to what is seen in depression alone. We will also investigate whether reward dysfunction and/or emotional reactivity to stress predicts depression and functioning at a one-month and two-month follow-up in cannabis-using depressed individuals, and whether one process is more relevant than the other in predicting outcomes. Increasing legalization of cannabis and thereby easier access may lead to greater cannabis use in depression. As such, the results of this study have implications for how co-occurring cannabis use in and depression can be treated, informing the development of more targeted treatments or prioritizing existing treatments that either normalize reward function or emphasize stress management.