Directional Effects of Anxiety and Depressive Disorders with Substance Use: a Review of Recent Prospective Research

Purpose of Review: Anxiety and depressive disorders are highly prevalent, frequently comorbid, and contribute to high rates of disability and death globally. They also commonly co-occur with substance use, including alcohol, cigarettes, and cannabis. Yet, the directionality for the onset and progression of these conditions is not fully understood. The present review highlights key findings from recent longitudinal studies on the prospective associations between anxiety and depressive disorders and the most commonly used substances (alcohol, tobacco, and cannabis). Additionally, this article reviews the potential of each condition to affect the outcome, course, and treatment of the other. Recent Findings: The current literature remains mostly inconclusive on the temporal associations between anxiety and depressive disorders and substance use and reverse causality, with some studies supporting the self-medication hypothesis and other work supporting the substance-induced hypothesis or the shared-vulnerability hypothesis. Summary: Future prospective work that utilizes sophisticated research designs to test proposed causality is crucial to inform treatment of comorbid anxiety/depressive disorders and substance use.