Mendelian Randomization Found No Genetic Link Between Cannabis Use Disorder and Cancer Risk | Research

The takeaway

A Mendelian randomization study found no causal association between cannabis use disorder and any cancer type, while opioid use disorder was linked to bladder cancer, leukemia, and ovarian cancer risk.

oncology researchers, genetic epidemiologists, cannabis safety researchers

What the researchers found

No significant causal relationship was found between CUD and any cancer type (all P>0.05). OUD showed potential causal associations with bladder cancer (OR 1.040), acute myeloid leukemia (OR 0.931), and ovarian cancer (OR 0.937). Reverse MR found no evidence of cancers causing OUD.

Why it matters

While observational studies have suggested links between cannabis use and cancer, this MR study uses genetic variants as instrumental variables to test causality, finding no support for a CUD-cancer connection.

The numbers in context

CUD: no significant association with any cancer (all P>0.05). OUD: bladder cancer OR 1.040 (P=0.029), AML OR 0.931 (P=0.005), ovarian cancer OR 0.937 (P=0.010). Data from FinnGen and UK Biobank GWAS.

How the study worked

Two-sample Mendelian randomization using GWAS summary statistics from FinnGen and UK Biobank. Inverse-variance weighted primary analysis with sensitivity analyses. Tested both CUD and OUD as exposures with multiple cancer types as outcomes.

What this study cannot tell us

MR assumptions may not be fully met. CUD GWAS instruments may lack power. Predominantly European-ancestry populations. Cannot assess dose-response or specific cancer subtypes in detail. Adjusted P-values did not reach significance for OUD associations.

How to read the evidence

MR design provides stronger causal inference than observational studies, but CUD instrument limitations and European-ancestry bias limit to moderate.

When this study was published

Uses current GWAS data from FinnGen and UK Biobank.

The bigger picture

The null finding for CUD and cancer is reassuring but should be interpreted cautiously. MR studies depend on the strength and specificity of genetic instruments, which may be limited for CUD given current GWAS sample sizes.

Questions still open

Would larger CUD GWAS improve power to detect cancer associations?
Does cannabis consumption method (smoking vs. edibles) differentially affect cancer risk?

Common questions

Does cannabis cause cancer?

This genetic study found no causal link between cannabis use disorder and any cancer type. However, this does not address whether cannabis smoke itself (as a route of exposure) might increase cancer risk.

What is Mendelian randomization?

A method using genetic variants associated with an exposure (like CUD) as natural experiments to test whether the exposure causes an outcome (like cancer), providing stronger evidence than typical observational studies.

Read the original research

Decoding the genetic links between substance use disorder and cancer vulnerability.

Psychopharmacology, 242(9), 2021-2033

View on PubMed ↗Publisher’s paper ↗

Citation

Su, Xin; Mo, Xiaoyan; Kan, Jun; Yang, Fan; Zhang, Bei; Huang, Yuanyuan. (2025). Decoding the genetic links between substance use disorder and cancer vulnerability.. Psychopharmacology, 242(9), 2021-2033. https://doi.org/10.1007/s00213-025-06781-3