Medical and non-medical marijuana use in depression: Longitudinal associations with suicidal ideation, everyday functioning, and psychiatry service utilization

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 nonmedical 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. Conclusions: Marijuana use, especially non-medical use, among patients with depression may impede depression symptom improvement while lessening the likelihood of psychiatry visits. Marijuana use and associated barriers to care should receive consideration by depression treatment providers.