A major international review of existing research has found a strong link between cannabis use disorder and major depressive disorder.
The analysis, which pooled data from 55 studies involving more than 3.2 million people, found that nearly 32 percent of individuals with cannabis use disorder also had major depression. Conversely, more than 10 percent of people with depression also reported cannabis use disorder.
Researchers say these rates are considerably higher than in the general population. The link persisted even when the two conditions did not occur at the same time.
The review does not prove one causes the other. It could be that cannabis use raises depression risk, or that people with depression self-medicate with cannabis. Shared genetic or environmental factors may also play a role.
Clinically, the findings underscore the need to screen for both conditions together. Experts say psychological therapies like cognitive behavioral therapy show promise for treating co-occurring cannabis use disorder and major depressive disorder.