Cannabis side effects in cancer patients most commonly affect the nervous system and mind | Research

The takeaway

A scoping review of 152 studies found cannabis-related adverse events in cancer patients most commonly involved the nervous system, psychiatric effects, and GI symptoms, with significant under-reporting across studies.

People interested in the safety of cannabis use during cancer treatment.

152 studies reviewed; nervous system AEs reported in 118

What the researchers found

Across 152 studies, the most common adverse events were nervous system-related (118 studies), psychiatric (101 studies), and gastrointestinal (81 studies). THC-CBD combinations were the most common formulation studied (69 studies), followed by synthetic THC (47) and single-compound THC (42). Oral and inhalation were the primary administration routes.

Why it matters

With cancer patients increasingly using cannabis for symptom management, this is the most comprehensive mapping of adverse events to date. The finding of significant under-reporting in many studies highlights a critical gap that could lead to underestimating risks.

The numbers in context

152 studies included. 61 RCTs. Most common cancer types: GI/liver/peritoneal (98 studies), hematological (92). Most common use: nausea/vomiting (78), pain (37). Nervous system AEs in 118 studies. Psychiatric AEs in 101. GI AEs in 81.

How the study worked

Systematic scoping review following JBI methodology. Six databases searched from inception to May 2023. Included 152 primary studies: 61 RCTs, 26 non-randomized trials, 23 case reports, and other designs. All studies reported adverse events from cannabis-based products in cancer care settings.

What this study cannot tell us

Scoping review maps evidence but does not assess quality or pool effect sizes. Diverse study designs, patient populations, and cannabis products limit comparability. Under-reporting of adverse events in original studies means the true burden may be higher.

How to read the evidence

Comprehensive scoping review with rigorous methodology, but the underlying evidence base consists of diverse study designs with variable reporting quality.

When this study was published

Published in 2024 covering literature through May 2023.

The bigger picture

As cannabis use in cancer care grows, having a comprehensive picture of potential side effects is essential. This review reveals that while cannabis-related adverse events are common, the quality of reporting is often poor, making it difficult to accurately assess risks for specific patient populations.

Questions still open

Are adverse events more common with THC-dominant versus CBD-dominant products in cancer patients? Does the route of administration affect the adverse event profile? Would standardized reporting requirements improve our understanding of cannabis safety in oncology?

Common questions

What are the most common side effects of cannabis in cancer patients?

Nervous system effects (like drowsiness and dizziness), psychiatric effects (like mood changes and confusion), and gastrointestinal symptoms were the three most commonly reported categories across 152 studies.

Are cannabis side effects in cancer patients well documented?

Not as well as they should be. The review found significant under-reporting and low-quality reporting of adverse events in many studies, suggesting the true extent of side effects may be underestimated.

Read the original research

Adverse events associated with the use of cannabis-based products in people living with cancer: a systematic scoping review.

Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer, 33(1), 40

View on PubMed ↗Publisher’s paper ↗

Citation

Cheah, Irene; Hunter, Jennifer; Gelissen, Ingrid; Chan, Wai-Jo Jocelin; Harnett, Joanna E. (2024). Adverse events associated with the use of cannabis-based products in people living with cancer: a systematic scoping review.. Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer, 33(1), 40. https://doi.org/10.1007/s00520-024-09087-w