Effectiveness of THC-containing cannabis for inflammatory bowel disease: a systematic review

Patients with inflammatory bowel disease (IBD) increasingly use cannabis. Studies investigating the effectiveness and safety of cannabis as a therapeutic option for IBD have reported conflicting findings, and recent reviews have not incorporated evidence from real-world studies. This systematic review assessed controlled non-interventional studies and interventional trials evaluating the effectiveness of delta-9-tetrahydrocannabinol (THC)-containing cannabis products in patients with IBD.

The systematic review procedures-including search strategy across four databases, literature screening, data extraction, qualitative result synthesis, and risk of bias assessment-followed the Cochrane Handbook and adhered to PRISMA-compliant reporting. We used the GRADE approach to rate evidence quality for each outcome.

peer-reviewed research on effectiveness or safety of cannabis as treatment modality, control group must be present, quantitative measure of effect/safety on IBD.

published before 2000, non-English, non-human research, non-cannabis/THC exposures, < 0.3% THC exposure, topical formulations.

Four randomized clinical trials (RCTs), and four non-interventional studies met all inclusion criteria. Non-interventional studies exhibited serious or critical risk of bias, leading to their exclusion from evidence ratings. The four RCTs demonstrated high risk of bias, although their evidence quality ratings varied. RCTs assessed adverse events; however, limited safety information was provided. Improvements in one trial were reported for bloating (n = 56) and appetite (n = 56), both rated as low evidence quality. Results for clinical disease activity scores (4 trials, n = 180), daily function, general well-being, general effect on health (1 trial, n = 56), bowel movement frequency (3 trials, n = 148), generic quality of life (3 trials, n = 122) and pain (2 trials, n = 88) were mixed. The outcomes of remission (3 trials, n = 150), weight (1 trial, n = 56), IBDQ (1 trial, n = 60), endoscopic scores (2 trials, n = 88), and nausea (1 trial, n = 56), consistently failed to differ meaningfully between intervention and control. The evidence quality rating for these null or inconclusive results varied from low to medium, with the exception of weight, rated as high, though no effect was reported.

Current evidence is inconclusive as to whether THC-containing cannabis products might have a positive effect in IBD, given heterogenous findings and mostly low-to-moderate evidence quality. Higher quality cannabis research is needed given widespread utilization.

PROSPERO: CRD42023411910.