Association between cannabis use and risk of diabetes mellitus type 2: A systematic review and meta-analysis

Background: Cannabis consumption exerts multiple effects on metabolism via various pathways, including glucose regulation and insulin secretion. Studies concerning the association between cannabis use and diabetes mellitus type 2 are discrepant. Objective: This study was conducted to evaluate the association between cannabis use and type 2 diabetes mellitus (T2DM). Search Methods: We searched PubMed, Scopus, Embase, Proquest, Web of Science, and Cochrane Library with no time, language or study types restriction until July 1, 2022, using various forms of "cannabis" and "diabetes mellitus" search terms. Selection Criteria: Randomized control trials, cohort, and case-control studies investigating the relationship between cannabis consumption and diabetes mellitus type 2 were included. Data Collection and Analysis: The Newcastle-Ottawa scale was used to assess the quality of studies. We pooled odds ratio (OR) with 95% confidence interval (CI) using the random-effects model, generic inverse variance method, DerSimonian and Laird approach. Main Results: A meta-analysis of seven studies, containing 11 surveys and 4 cohorts, revealed that the odds of developing T2DM in individuals exposed to cannabis was 0.48 times (95% CI: 0.39 to 0.59) lower than in those without cannabis exposure. Conclusions: A protective effect of cannabis consumption on the odds of diabetes mellitus type 2 development has been suggested. Yet given the considerable inter-study heterogeneity, the upward trend of cannabis consumption and cannabis legalization is recommended to conduct studies with higher levels of evidence.