239: Harms of Inhaled Cannabis: A Systematic Review and Meta-Analysis of Observational Studies

Topic: Clinical Science
Subtopic: Non-specific to any diagnosis, Pharmacological treatments, Treatment/management

Background and Aims: Cannabis products are increasingly used to manage chronic pain and other symptoms; As it became increasingly commercialized, inhalation via joints, bongs, pipes, and vapes have emerged as a major mode of use for both medical and recreational purposes [1]. However, the literature on harms associated with this route of use is limited. We conducted a systematic review and meta-analysis of observational studies to explore the harms associated with inhaled cannabis.

Methods: We searched MEDLINE, EMBASE, PsychInfo, and Web of Science for observational studies reporting on harms or adverse events associated with inhaled cannabis use (medical or recreational), from inception to May 30, 2025. Paired reviewers independently screened eligible studies, assessed risk of bias and extracted data. We pooled the prevalence of adverse events using Freeman-Tukey transformation and random-effects model. We pooled the risk between inhaled and non-cannabis users using odds ratios (ORs) and 95% confidence interval (CI). We conducted a priori subgroup analysis to explore the source of heterogeneity.

Results: We identified 31 studies with 62,463 cannabis users reporting 90 adverse events. Meta-analyses showed that inhaled cannabis use may cause fatigue (38% [31-45%]), cough (26%, 95%CI [6-53%]), anxiety (22% [15-31%]), paranoia (15% [7-25%]), amnesia (19% [8-31%]), dizziness (13% [7-19%]), and dry mouth (47% [35-60%]). Inhaled cannabis versus non-users may increased risks: wheezing (OR 2.45, 95%CI [1.87-3.20]), cough (OR 2.02 [1.23-3.32]), and depression (OR 2.07 [1.01-4.23]); but not for shortness of breath (OR 1.16 [0.75-1.78]) and lung cancer (OR 1.45 [0.89-2.39]).

Conclusions: Our review found inhaled cannabis users frequently experienced fatigue, coughing, anxiety, paranoia, amnesia, dizziness, and dry mouth. Compared to non-users, individuals using inhaled cannabis products are twice as likely to report wheezing, cough and depression. Our findings will support shared decision-making for patients considering inhaled cannabis products for therapeutic purposes. Future studies should explore long-term harms associated with inhaled cannabis use.

References: 1. Lurie JM, Javaid A. Visualizing Global Chronic Pain. Anesthesia & Analgesia. 2024;138(4):918. doi:10.1213/ANE.0000000000006564

Presenting Author: Jason Busse
Submitting Author: Wenjun Jiang

Senior Author: Jason Busse

IASP 2026 Global Year theme of Neuropathic Pain: No

• Jane Jomy: MSc - University of Toronto
• Abigail Chu - University of Waterloo
• Mona Elmikaty - McMaster University
• Rachel Couban: MISt - McMaster University
• Li Wang: PhD - McMaster University
• Jason Busse: PhD - McMaster University