Impact of cannabis use on long-term remission in bipolar I and schizoaffective disorder

Sung-Wan Kim, Seetal Dodd, Lesley A Berk, Jayashri Kulkarni, Anthony De Castella, Paul B Fitzgerald, Jae-Min Kim, Jin Sang Yoon, Michael Berk

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Objective To investigate the impact of regular cannabis use on long-term remission of mood symptoms in bipolar spectrum disorders. Methods The 24-month prospective observational study included patients (n=239) with bipolar I disorder and schizoaffective disorder, bipolar type. Participants were classified as regular cannabis users (three times or more per week) or non-users. The primary outcome measure was the achievement of remission on the evaluations during the 24 months. Results Of the 234 participants for whom data was available, 25 (10.7%) were regular cannabis users, and the group comprised significantly more males than females. In the total population, cannabis use was significantly associated with decreased likelihood of remission during the 24-month follow-up period. Subgroup analyses showed that cannabis use was significantly associated with lower remission rates on the Hamilton Depression Rating Scale in females (n=139) and patients prescribed mood stabilizers alone (n=151), whereas in males (n=95) and patients prescribed olanzapine and/or a mood stabilizer (n=83), cannabis use was significantly associated with lower remission rates on the Young Mania Rating Scale. Remission rates were lowest in the concurrent cannabis and tobacco smoking group (n=22) followed by the tobacco smoking only group (n=97), and the non-smoker group (n=116). The post-hoc analysis revealed that all remission rates were significantly lower in the concurrent cannabis and the tobacco smoking group compared to the non-smoker group. Conclusion Cannabis use negatively affects the long-term clinical outcome in patients with bipolar spectrum disorders. A comprehensive assessment and integrated management of cannabis use are required to achieve better treatment outcomes for bipolar spectrum disorders.

Original languageEnglish
Pages (from-to)349-355
Number of pages7
JournalPsychiatry Investigation
Issue number3
Publication statusPublished - 1 Jul 2015


  • Bipolar disorder
  • Cannabis
  • Observational study
  • Remission
  • Schizoaffective disorder
  • Substance

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