Although one third of patients with Bipolar Disorder have an addiction to Cannabis or an abused consumption, the interaction between cannabis use and bipolar disorder remains controversial.

To evaluate the use of cannabis among patients with Bipolar Disorder and to compare the socio-demographic and clinical characteristics between patients who are consumers and non-consumers.

This is a retrospective, descriptive study including all patients treated for type I bipolar disorder in the psychiatric department of Tahar Sfar Hospital of Mahdia (Tunisia). In addition to socio-demographic and clinical characteristics, we collected data on cannabis use (age at first consumption and frequency of consumption).

Our study population consisted of 84 male patients followed for bipolar I disorder. The mean age was 36.8 ± 11.3 years. Among these patients, 23 (27.8%) had regular cannabis use. The average age at first consumption was 21.6 ± 7.2 years. Bipolar patients with regular cannabis consumption had an earlier age of onset of the disorder (p = 0.02). They had higher numbers of manic episodes (p = 0.05), higher number of manic episodes with severe intensity (p = 0.04), higher number of manic episodes with mixed characteristics(p = 0.04), a higher number of hospitalizations (p = 0.01) with longer hospital stays (p = 0.02).

Cannabis use among patients with type 1 bipolar disorder is associated with an unfavorable course of the disorder. Early diagnosis and appropriate management of this comorbidity seem to be essential for improving the prognosis of bipolar disorder.