Adverse events and cannabinoid use in cancer management: systematic review.

Background: Cannabinoid-based therapies are increasingly used in cancer care to manage symptoms such as pain, chemotherapy-induced nausea and distress in palliative settings. Despite their clinical adoption, the safety profiles of these therapies remain incomplete. This systematic review synthesises randomised controlled trials (RCTs) reporting adverse events (AEs) associated with cannabinoid-based therapies in adult patients with cancer. Methods: We searched PubMed, CINAHL and Web of Science for studies published between January 2015 and March 2025. Eligible studies included RCTs involving adult patients with cancer receiving cannabinoid-based treatments that reported AEs. Data were extracted on study characteristics, intervention type and AEs, which were categorised by systemic disorder. Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines were followed throughout. Results: 14 RCTs were included. Studies varied in sample size (12 to 399), intervention duration (48 hours to 12 months), and cannabinoid formulations. All studies reported AEs, with the most frequent involving gastrointestinal (eg, nausea, dry mouth), neurological (eg, dizziness, somnolence) and psychiatric (eg, anxiety, hallucinations) disorders. The number of distinct AEs reported per study ranged from 1 to more than 12. Risk of bias assessments revealed that 10 studies had 'some concerns' and 2 were classified as 'high risk' due to incomplete outcome reporting or selective bias. Conclusions: Cannabinoid therapies are associated with a broad range of AEs in adult patients with cancer, particularly affecting the gastrointestinal and nervous systems. While these therapies may offer symptomatic relief, clinicians must weigh benefits against potential harms. Further studies with larger samples, longer follow-ups and standardised AE reporting are recommended.