Effects of co-occurring cannabis use disorders on the course of bipolar disorder after a first hospitalization for mania.

CONTEXT Cannabis use disorders commonly co-occur in bipolar disorder; however, the effects of cannabis abuse on outcome have been minimally studied. OBJECTIVE To identify how the sequence of the onsets of a cannabis use disorder and bipolar disorder is associated with the subsequent course of each condition. DESIGN Inception cohort. SETTING Academic medical center. PATIENTS Patients (N = 144) were studied who met criteria for bipolar I disorder (manic or mixed), were 12 to 45 years old, and had no previous hospitalizations and minimal previous treatment. Patients were followed up for up to 5 years and included 33 in whom the onset of a cannabis use disorder preceded the onset of bipolar disorder (cannabis first), 36 in whom bipolar disorder onset preceded the onset of cannabis abuse (bipolar first), and 75 with bipolar disorder only. MAIN OUTCOME MEASURES Symptomatic recovery and recurrence of both conditions and percentage of follow-up time with affective and cannabis use disorder symptoms. RESULTS The cannabis first group exhibited better recovery than the other groups, although when adjusted for potential mediator variables these results did not persist. Cannabis use was associated with more time in affective episodes and with rapid cycling. Most cannabis use disorders remitted immediately after hospitalization, followed by rapid rates of recurrence. CONCLUSIONS The effects of the sequence of onsets of bipolar and cannabis use disorders were less pronounced than observed in co-occurring alcohol and bipolar disorders. Aggressive drug abuse treatment immediately after a first psychiatric hospitalization might decrease rates of recurrence and new cases of cannabis use disorder in the course of bipolar disorder.