Cannabis use disorder (CUD) is associated with a more severe illness course among patients with bipolar disorder (BD), researchers report.
Shaul Lev-Ran (Centre for Addiction and Mental Health, Toronto, Ontario, Canada) and colleagues also found that BD patients with co-occurring CUD were more likely than those without to use other substances and have antisocial personality disorder.
The researchers studied data on 1905 individuals, aged 18 years and older, with BD who participated in the National Epidemiological Survey of Alcohol and Related Conditions (NESARC) 2001-2002, which comprised a nationally representative sample of 43,093 individuals.
Overall, 7.2% (n=119) of BD patients fulfilled criteria for DSM-IV-defined CUD in the previous 12 months compared with 1.2% of NESARC participants without the mood disorder.
Among individuals with BD, those with co-occurring CUD (n=119) were mostly men (62%), aged 18-29 years (70%), high-school educated (67%), unmarried (57%), and living in a rural area (60%).
After accounting for age, gender, and other sociodemographic variables, the team found that patients with BD and co-occurring CUD were at increased risk for nicotine dependence (adjusted odds ratio (AOR)=3.8), alcohol use disorder (AOR=6.6), any drug disorder (AOR=11.9), and any personality disorder (AOR=2.36), compared with BD patients without CUD (n=1786).
BD patients with co-occurring CUD also had a significantly higher median number of mood episodes per year than other BD patients, at 1.8 versus 0.7, as well as an earlier age at onset of a first manic (19.5 vs 25.1 years) or depressive (18.5 vs 24.4 years) episode.
Lev-Ran et al conclude: "Co-occurring CUD is associated with significant co-morbidities and a more severe course of illness among individuals with bipolar disorder."
They suggest: "Comprehensive evaluation of patients with bipolar disorder (especially males) should include a systematic assessment of substance use disorders, including CUD."
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