Effects of Perioperative Cannabis Use on Bariatric Surgical Outcomes: a Systematic Review

While cannabis is the most commonly used non-prescription drug in the USA and has established effects on weight, its implication for bariatric surgery has not been formally evaluated. We aimed to review the current literature on perioperative cannabis use in patients undergoing bariatric surgery.

Our systematic search of MEDLINE and Embase until March 2020 returned 169 citations. Screening and abstraction of results were performed in duplicate, and qualitative synthesis of the data was performed. Primary outcomes were cannabis use characteristics, weight loss outcomes, and 30-day postoperative morbidity. Study quality was assessed through the MINORS risk-of-bias tool.

Six observational studies with a total of 1167 patients (78.6% female, median follow-up 12 months [3-38.4 months]) were included. A total of 9.9% of patients (n = 116/1167) used cannabis in the perioperative period. Compared with non-users, 1-year weight loss was significantly higher in a study evaluating 8 preoperative cannabis users (n = 8/239, p = 0.002); however, there were no differences in single-study data on 90-day total weight loss (n = 434, p = 0.89) nor 2-year excess BMI loss (n = 146, p = 0.631). There was no difference in 30-day minor (RR 0.91, 95%CI 0.49-1.71, p = 0.77) or major morbidity (RR 0.75, 95%CI 0.31-1.79; p = 0.50).

There are only uncontrolled studies to date on cannabis use in bariatric surgery. While these have reported conflicting effects on weight loss and no effect on morbidity to date, validation in randomized trials is required to facilitate evidence-based recommendations.