Using Pubmed and PsychInfo, we conducted a narrative review of the literature on cannabis and psychiatric comorbidity using the keywords cannabis, psychosis, mood, depression, mania, bipolar, and anxiety.

There is substantial evidence of an association between cannabis use and psychosis. A few reports suggest an association with bipolar disorder while the association with depression and anxiety disorders is mixed.

The present review confirms earlier findings of an association between cannabis use and a lower age at onset. Data shows that cannabis use, beginning in the adolescence and with a frequency higher than once a week, correlates with the development in adult age of affective symptoms and/or disorder, mainly in bipolar disorder, with a moderate relation with Depressive spectrum. Even more, some authors hypothesize that cannabis may play a role in the development of the disorder, that to say, affective disorder would not appear in the absence of cannabis use. The current findings suggest that recent cannabis use is associated with a more severe course of illness in the early phase of BD I.

Recent cannabis use was also associated with more lifetime suicide attempts.

The authors have not supplied their declaration of competing interest.