Cannabis Use in Bipolar Disorder Was Linked to Earlier Onset and More Psychosis, But Not More Relapses

Cannabis was associated with earlier onset of bipolar disorder, current manic polarity, presence of psychotic symptoms, and higher likelihood of discontinuing treatment. However, cannabis was NOT associated with higher rates of ER visits or hospital readmissions. Interestingly, tobacco use showed significantly higher readmission rates. Alcohol, cocaine, and stimulants showed no association with studied variables.

Prospective cohort study of 279 patients admitted to Hospital Clinic of Barcelona for manic or mixed episodes (2015-2019), with 3-year follow-up examining hospital readmissions, ER visits, and clinical characteristics.

The distinction between cannabis affecting illness severity (earlier onset, more psychosis) but not relapse rate (readmissions) is clinically important. It suggests cannabis may influence the type and quality of bipolar episodes more than their frequency.

This study adds nuance to the substance use and bipolar disorder literature by examining multiple substances and multiple outcomes simultaneously. The finding that tobacco, not cannabis, predicted relapse rate challenges assumptions about which substances are most harmful for bipolar prognosis.

Single-center study in Barcelona. Lacks detailed information on cannabis use patterns, history, and consumption amounts. Loss to follow-up from patients leaving the region or switching to private care. Cannot establish causation.