Cannabis use worsens bipolar disorder and major depressive disorder

Greater understanding of the effect of cannabis use on mood disorders is needed, given the increasing acceptability and legalization of cannabis in Canada. To investigate this issue, the Canadian Network for Mood and Anxiety Treatments (CANMAT) examined the association between cannabis use and incidence, presentation, course and treatment of bipolar disorder and major depressive disorder. A CANMAT Task Force first conducted a systematic literature review and used the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach to evaluate the quality of evidence. The Task Force then generated recommendations, while integrating clinical considerations. Read: Limited evidence supports the role of cannabis in pain relief Main findings: Of 12,691 potentially relevant publications, 56 met the criteria: 23 on bipolar disorder, 21 on major depressive disorder, 11 on both diagnoses and one on treatment of comorbid cannabis use disorder and major depressive disorder. Of 2,479,640 participants, 12,502 were comparison participants, 73,891 had bipolar disorder and 408,223 major depressive disorder without cannabis use. Of those with cannabis use, 2,761 had bipolar disorder and 5,044 major depressive disorder. The lifetime prevalence of cannabis use was 52% to 71% in bipolar disorder and 6% to 50% in major depressive disorder. Cannabis use was associated with worsening disease course and symptoms of both mood disorders. More consistent associations were found in bipolar disorder than in major depressive disorder, with increased severity of depressive, manic and psychotic symptoms in bipolar disorder and increased severity of depressive symptoms in major depressive disorder. Cannabis use was associated with increased suicidality and decreased functioning in both bipolar disorder and major depressive disorder. CANMAT Recommendations: Individuals with bipolar disorder should avoid the use of cannabis (Strong recommendation; moderate certainty of evidence). Individuals with major depressive disorder should avoid the use of cannabis. (Qualified recommendation due to inconsistency in the evidence; low–moderate certainty of evidence). Read: Cannabis use during pregnancy up 25% during the pandemic Enquire about cannabis use: Since cannabis use is associated with alterations in the course and outcome of bipolar disorder and depression, it is important for healthcare providers to enquire about cannabis use. Asking patients to complete a questionnaire can help identify cannabis use and cannabis use disorder. Clinicians should ask about: Course of use—age of onset and frequency of use Content—amount and concentration of different cannabis constituents Context of use—physical, social and psychological context of use (e.g., use of cannabis to reduce anxiety, agitation or pain; to enhance social interactions; to induce a sense of well-being in individuals with no pre-existing distress [recreational use]; or use in pregnancy). Use of cannabis during pregnancy is increasing and is associated with the presence of major depressive disorder. Clinicians should advise patients about the preliminary nature of data on the potential impact of cannabis use on the fetus and the signal of possible harmful effects. Use of other substances. Clinicians should discuss current information regarding cannabis use in mood disorders and the potential negative impact of cannabis use on the course of the disorder and clinical outcomes. If patients wish to reduce or stop cannabis use, clinicians can recommend psychosocial interventions, particularly motivational enhancement therapy and cognitive behavioural therapy (CBT), which have been associated with a reduction in cannabis use. Conclusion Cannabis use is associated with worsened course and functioning in bipolar disorder and major depressive disorder. Individuals with bipolar disorder or major depressive disorder should avoid the use of cannabis. Future studies should include more accurate determinations of the type, amount and frequency of cannabis use and select comparison groups to control for underlying common factors. Reference 1. Tourjman SV, Buck G, Jutras-Aswad D, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) Task Force Report: a systematic review and recommendations on cannabis use in bipolar disorder and major depressive disorder. Can J Psychiatry 2022; Published online June 16, 2022. https://doi.org/10.1177/07067437221099769

Cannabis use worsens bipolar disorder and major depressive disorder

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