312: Inhaled Cannabis for Chronic Pain: A Systematic Review and Meta-Analysis of Randomized Trials

Topic: Clinical Science
Subtopic: Pain category (ICD-11), Mixed pain, Pharmacological treatments

Background and Aims: Chronic pain affects one in five adults globally [1-3]. People often consume inhaled (i.e., smoking and vaporized) forms of medical cannabis; in 2024, dried flower/leaf remained the most common type of cannabis products consumed (63% of users), while vaporizers were the third most common type (37% of users) [4]. Despite widespread use, the benefits and harms of inhaled cannabis for chronic pain is uncertain. We conducted a systematic review and meta-analysis of randomized clinical trials (RCTs) to assess the effectiveness and safety of inhaled medical cannabis for chronic pain, and to address this evidence gap.

Methods: MEDLINE, EMBASE, AMED, PsycInfo, CENTRAL, CINAHL PubMed, Web of Science, Cannabis-Med, Epistemonikos, and trial registries were searched up to October 2025 to identify randomized trials comparing any form of inhaled cannabis (smoked or vaporized) for medical purposes in chronic pain patients. Paired reviewers independently assessed risk of bias, extracted data and evaluate the certainty of evidence using GRADE approach. We performed random-effects meta-analysis using weight mean difference (WMD) for continuous outcomes and relative risk (RR) for binary outcomes. We conducted a priori subgroup analyses and meta-regressions to explore sources of heterogeneity.

Results: We included 13 trials comprising 395 adults with chronic non-cancer pain; median follow-up was 1.6 days (IQR 5 hours to 5 days). Moderate- to high-certainty evidence shows that inhaled medical cannabis versus placebo probably provides short-term pain relief (WMD of -0.74cm on a 10cm visual analogue scale (VAS) [95%CI -1.06 to -0.43cm]; more patients achieving ≥30% pain reduction (RR 1.60 [95%CI 1.30 to 1.95]); but increased risk of dizziness (RD 10% [95%CI 3% to 25%]) and cough (RD 13% [95%CI 3% to 34%]); with little or no improvement in physical, emotional, role functioning, or sleep quality.

Conclusions: Compared to placebo, short-term use of inhaled cannabis for chronic non-cancer pain (≤ 5 days in 11 of 13 trials) probably provides clinically important pain relief for approximately 1 in 5 patients, but with little or no improvement in physical, emotional, or role functioning, or in sleep quality. Short term use also increases mild, transient adverse effects, particularly dizziness and cough. Evidence on longer term outcomes is lacking, and the comparative effectiveness of inhaled cannabis versus opioids or other active treatments remains uncertain. High quality, longer term trials are needed to clarify sustained benefits, risks, and its clinical role.

References: 1. Dahlhamer J, Lucas J, Zelaya C, et al. Prevalence of chronic pain and high impact chronic pain among adults – United States, 2016. MMWR 2018;67(36):1001–06.
2. Breivik H, Collett B, Ventafridda V, et al. Survey of chronic pain in Europe: prevalence, impact on daily life, and treatment. Eur J Pain 2006;10(4):287–333. doi: 10.1016/j.ejpain.2005.06.009 [published Online First: 20050810]
3. Sa KN, Moreira L, Baptista AF, et al. Prevalence of chronic pain in developing countries: systematic review and meta-analysis. Pain Rep 2019;4(6):e779. doi: 10.1097/PR9.0000000000000779 [published Online First: 2020/01/28]
4. Health Canada. Canadian Cannabis Survey 2024: Summary. Available at: https://wwwcanadaca/en/health-canada/services/drugs-medication/cannabis/research-data/canadian-cannabis-survey-2024-summaryhtml#a27

Presenting Author: Jason Busse
Submitting Author: Wenjun Jiang

Senior Author: Jason Busse

IASP 2026 Global Year theme of Neuropathic Pain: No

• Li Wang: PhD - McMaster University
• Vahid Ashoorion - McMaster University
• Kevin Shao - University of British Columbia
• Fares Hayek - Coronation Family Physicians
• Cody Tran - McMaster University
• Yiwei Chen - Cornell University
• Henry Kwon - Henry Ford Hospital
• Rachel J Couban - McMaster University
• Andea Darzi - McMaster University
• Jason W Busse: PhD - McMaster University