Associations between cannabis use disorder (CUD) and affective psychiatric illnesses are understudied. Researchers analyzed registry data from Danish persons ≥16 years old between 1995 and 2021 to examine the associations between CUD diagnosis and subsequent diagnoses of major depressive disorder (unipolar depression) and bipolar disorder, including psychotic and non-psychotic subtypes of each illness.
- Of the 6,651,765 persons (50 percent female) analyzed, 1 percent (n=60,696) were diagnosed with CUD and 4 percent (n=260,746) were diagnosed with an affective disorder over the study period.
- There was an increased risk of developing both psychotic depression (adjusted hazard ratio [aHR], 1.97) and nonpsychotic depression (aHR, 1.83) among persons with CUD compared with those without CUD.
- There was an increased risk of developing psychotic bipolar disorder (aHR, 4.05) and nonpsychotic bipolar disorder (aHR, 2.96 for men; aHR, 2.60 for women) among persons with CUD compared with those without CUD.
- Risk of developing an affective illness was highest within the first 6 months of CUD diagnosis for both unipolar depression and bipolar disorder, but the risk of developing either affective illness disorder remained elevated for 10 years following CUD diagnosis.
Comments: These data suggest that CUD is associated with an increased risk of developing both psychotic and nonpsychotic major depressive disorder and bipolar disorder, although a causal link has not been established. As cannabis use and CUD become increasingly prevalent, clinicians should be aware that patients with CUD may have higher likelihood of developing affective illnesses.