Cannabis use jumped 52% after weight-loss surgery, and people drinking hazardously were most likely to start | Research

The takeaway

Among 612 bariatric surgery patients in Michigan, cannabis use prevalence increased 52.4% from before to after surgery, with nearly half of post-surgery users being new initiates.

Bariatric surgery patients and candidates, addiction researchers, surgical teams

52.4% increase in cannabis use after bariatric surgery

What the researchers found

Post-bariatric surgery cannabis use rose from roughly 10.5% to 16%, a 52.4% relative increase. Of those using cannabis after surgery, 45.9% had not used before. Hazardous alcohol use tripled the odds of both initiating and continuing cannabis use post-operatively.

Why it matters

Bariatric surgery patients are known to sometimes shift addictive behaviors after the procedure. This is one of the first studies to document how cannabis use specifically changes around surgery, which matters as cannabis becomes more accessible in legal states.

The numbers in context

612 participants; 52.4% relative increase in cannabis use (p = .0001); 16% reported post-operative use; 45.9% were new initiates; among initiates, 11.8% screened positive for hazardous use; hazardous alcohol users had 2.8x odds of initiating cannabis (95% CI: 1.4-5.4) and 3.0x odds of persisting (95% CI: 1.6-5.8)

How the study worked

Cross-sectional survey of 612 patients who had metabolic and bariatric surgery (MBS) between 2018 and 2021 at a single Michigan health system. Participants completed online surveys about cannabis, alcohol, and other substance use, psychiatric symptoms, and demographics.

What this study cannot tell us

Single health system in a legal-cannabis state limits generalizability. Self-reported data subject to recall bias. Cross-sectional design cannot establish causality. No control for specific surgical procedures or weight loss outcomes.

How to read the evidence

Moderate: decent sample size from a single institution with validated screening tools, but cross-sectional design and self-reported data.

When this study was published

2026 study using 2018-2021 patient data from Michigan.

The bigger picture

This fits into growing research on "addiction transfer" after bariatric surgery, where patients sometimes replace food-related behaviors with substance use. Understanding cannabis as part of this pattern is increasingly relevant in states with legal access.

Questions still open

Does post-surgical cannabis use affect weight loss outcomes? Are patients using cannabis to manage post-surgical pain or nausea, or for recreational purposes? Would screening and intervention programs reduce hazardous use patterns?

Common questions

Why might cannabis use increase after bariatric surgery?

Researchers suggest it could serve as a coping mechanism, replacing food-related behaviors. Cannabis legalization during the study period may also have played a role, though most patients underwent surgery after legalization.

Is post-surgery cannabis use harmful?

The study found that 11.8% of new initiates and 19.2% of continuing users screened positive for hazardous cannabis use, but long-term effects on surgical outcomes were not measured.

Read the original research

Cannabis use before and after metabolic and bariatric surgery and its association with alcohol use.

Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery

View on PubMed ↗Publisher’s paper ↗

Citation

Vanderziel, Alyssa; Killian, Samantha J; Haley, Erin N; Braciszewski, Jordan M; Teotia, Arjun; Brescacin, Carly; Carlin, Arthur M; Varban, Oliver; Miller-Matero, Lisa R. (2026). Cannabis use before and after metabolic and bariatric surgery and its association with alcohol use.. Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery. https://doi.org/10.1016/j.soard.2025.11.027