Abstract

Background Marijuana use is clinically problematic in depression, and non-medical and medical use may both contribute to barriers to care in this population. Among outpatients with depression, we examined the differential impact of medical or non-medical marijuana use, relative to no-use, on psychopathology and service use over time.

Method Participants were 307 psychiatry outpatients participating in a trial of drug/alcohol use treatment for depression. Measures of past 30-day marijuana use, depression/anxiety symptoms, psychiatry visits, and functional data related to health status were collected at baseline, 3, 6, and 12 months. Regressions (baseline and 1 year) and growth models (over time) predicted clinical and psychiatry visit outcomes, from medical or non-medical marijuana use (no-use = reference).

Results At baseline, 40.0% of the sample used marijuana and more reported non-medical (71.7%) than medical (28.2%) use. Relative to non-users at baseline, patients using medically had worse mental/physical health functioning (p's < 0.05), and non-medical use was associated with higher suicidal ideation (B = 1.08, p = .002), worse mental health functioning (B = -3.79, p = .015), and fewer psychiatry visits (B = -0.69, p = .009). Patients using non-medically over time improved less in depression symptoms (B = 1.49, p = .026) and suicidal ideation (B = 1.08, p = .003) than non-users.

Limitations Participants were psychiatry outpatients, limiting generalizability.