Patterns of Marijuana Use Among Psychiatry Patients with Depression and Its Impact on Recovery

Background and Purpose: Marijuana increasingly takes center stage in public policy and debate as legislation to legalize spreads and use for medical purposes is already established in many states.  Attitudes towards liberalization are normalizing, and patients with a variety of health conditions, including psychiatric conditions, may be more likely to ask their health care providers about whether marijuana has harmful or beneficial effects on health.  Recent research suggests marijuana use may impede the recovery of vulnerable populations, including psychiatry patients with depression.  Depression is associated with substance-related problems that worsen depression-related disability.  Marijuana is frequently used by patients with depression, yet the degree to which its use contributes to significant barriers to recovery in this population has been understudied.  This study examined longitudinal patterns and predictors of marijuana use and associations between use, symptoms and functional outcomes in a large, heterogeneous sample of psychiatry patients with depression.  Method: Participants were 307 psychiatry outpatients with depression who were recruited from Kaiser Permanente Alameda Center Department of Psychiatry in Union City and Fremont, CA; assessed at baseline, 3-, and 6-months on symptom (PHQ-9 and GAD-7), functioning (SF-12) and past-month marijuana use for a substance use intervention trial.  Longitudinal growth models examined patterns and predictors of marijuana use and its impact on symptom and functional outcomes.  Results:  A considerable number of (40.7%; n = 125) patients used marijuana within 30-days of baseline. Over 6-months, marijuana use decreased (B = -1.20, p < .001), but patterns varied by demographic and clinical characteristics.  Depression (B = 0.03, p < .001) symptoms contributed to increased marijuana use over the follow-up, and those aged 50+ (B = 0.44, p < .001) increased their marijuana use compared to the youngest age group. Marijuana use worsened depression (B = 1.24, p < .001) and anxiety (B = 0.80, p = .025) symptoms; marijuana use led to poorer mental health (B = -2.03, p = .010) functioning. Medical marijuana (26.8%; n = 33) was associated with poorer physical health (B = -3.35, p = .044) functioning. Conclusions and Implications:  Marijuana use is common and associated with poor recovery among psychiatry outpatients with depression.  Assessing for marijuana use and addressing use among subgroups with depression who are particularly vulnerable to negative effects of the drug (e.g., older adults, patients with high depression severity, etc.) may help improve outcomes.  Social workers have a unique opportunity to secure an integral role in assessing and addressing marijuana use in the context of psychiatric outpatient treatment and considering its use for at risk groups in light of its impact on recovery.