Cannabis Use Disorder (CUD) may increase the risk of unipolar depression and bipolar disorder, both in their psychotic and nonpsychotic forms, according to a population-based cohort study published in JAMA Psychiatry, 2023. The study used Danish nationwide registers to analyse the link between cannabis use and mental health disorders, following 6,651,765 individuals, both male and female, over a span of 119,526,786 person-years.
The study found that CUD was associated with an elevated risk of unipolar depression, with hazard ratios (HR) of 1.84 for overall unipolar depression, 1.97 for psychotic unipolar depression, and 1.83 for nonpsychotic unipolar depression. Similarly, an increased risk of bipolar disorder was observed in both men (HR, 2.96) and women (HR, 2.54), with psychotic bipolar disorder exhibiting an HR of 4.05. Interestingly, CUD was associated with a higher risk for psychotic than nonpsychotic subtypes of bipolar disorder, but this differential risk was not observed for unipolar depression.
The study underscores the potential mental health risks associated with cannabis use, offering significant insights that could shape policies concerning cannabis use and legality. However, further research is necessary to expand our understanding of the relationship between cannabis use and affective disorders.