Cannabis Did Not Appear to Weaken Immune Markers Relevant to Cancer Immunotherapy

What the researchers found

Analysis of 40 clinical studies (including 9 RCTs) found no change in cytokines, T-cell counts, or CRP in most studies with cannabis exposure. Among autoimmune disease patients, cannabis improved clinical symptoms while objective immune markers remained unchanged. Immune markers relevant to checkpoint inhibitor function did not appear associated with cannabis use.

Why it matters

Many cancer patients use cannabis for symptom management while receiving immunotherapy. Preclinical data suggesting cannabis causes immunosuppression has raised concerns, but this clinical review found no evidence that translates to meaningful immune changes in humans.

The numbers in context

40 studies included, 9 RCTs. No change in cytokines, T-cell counts, or CRP in most studies. Clinical symptom improvement in autoimmune patients despite unchanged immune markers. No evidence of altered immune parameters relevant to ICI function.

How the study worked

Systematic review searching Ovid Medline for clinical studies investigating cannabis use in humans and the immune system. Preclinical studies and case reports were excluded. Forty studies met criteria, including 9 randomized placebo-controlled trials.

What this study cannot tell us

Most included studies were not specifically designed to assess cannabis-immunotherapy interactions. Heterogeneous cannabis exposure definitions. Few studies focused on cancer patients receiving ICIs specifically.

How to read the evidence

Moderate: systematic review of 40 studies including 9 RCTs, but most studies were not designed to test cannabis-immunotherapy interactions specifically

When this study was published

Published in 2025

The bigger picture

The gap between preclinical immunosuppression findings and clinical null results suggests that cannabis effects on immunity may be more nuanced in humans than lab studies indicate. This is reassuring for the growing number of cancer patients using both cannabis and immunotherapy.

Questions still open

• Would prospective studies in ICI-treated patients confirm these findings? Do specific cannabinoids (THC vs CBD) differ in their immune effects? Could cannabis even enhance immunotherapy through anti-inflammatory pathways?

Common questions

Read the original research

The impact of cannabis on immune checkpoint inhibitor therapy: a systematic review of immunomodulatory effects of cannabis in patients with and without cancer.

Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer, 33(3), 166

Citation

Behling-Hess, Caroline; Simonson, Grant; Salz, Talya; Fleege, Nicole; Zylla, Dylan. (2025). The impact of cannabis on immune checkpoint inhibitor therapy: a systematic review of immunomodulatory effects of cannabis in patients with and without cancer.. Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer, 33(3), 166. https://doi.org/10.1007/s00520-025-09218-x

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