A post-hoc analysis of data from a prospective European study reveals that patients with bipolar disorder who stop using cannabis during a manic or mixed episode have similar clinical and functional outcomes to those who have never used the drug.
Writing in Acta Psychiatrica Scandinavica, the authors report: “We found that continued cannabis use was associated with less chance of recovery and remission after an acute manic/mixed episode and a higher risk of recurrence than never use of cannabis.”
Cannabis use is thought to worsen the course of illness in bipolar disorder, but no previous studies have prospectively examined the impact of stopping cannabis use compared with never having used the drug or continuing to use it, the researchers explain.
They analysed data from the 2-year European Mania in Bipolar Longitudinal Evaluation of Medication (EMBLEM) study to identify 1922 patients with manic or mixed episodes of bipolar disorder who had completed the study and for whom information about cannabis use was available.
Use of cannabis was based on self-report and the patients were stratified into the 4.6% who were previous users (use only during the initial 12-week acute phase of the study), 6.9% who were current users (any use between 12 weeks and 24 months) and 88.5% who were never users.
Cannabis use status affected clinical outcome, with previous users having the highest rates of remission (68.1%) and recovery (38.7%), as well as the lowest rates of recurrence (42.1%) and relapse (29.8%).
In logistic regression analysis, previous users had similar outcomes to never users, whereas current users had lower recovery and remission rates, higher recurrence rates, reported greater work impairment and were less likely to live with a partner.
Although drugs other than cannabis are also known to have deleterious effects on outcomes, “[a]fter controlling for alcohol and other substance use, the increased risk of recurrence and not living together with a partner was maintained in the current cannabis use group”, lead author Ana González-Pinto (Hospital Santiago, Vitoria, Spain) and colleagues report.
Clinicians should consider implementing holistic management plans for bipolar patients that include psychoeducation and other treatments for stopping cannabis, alcohol and other drug use, they conclude.
This article first appeared on ‘medwire News’ on 4 December 2014.