Cannabis Dependence Not Linked to Higher Cancer Mortality, Unlike Alcohol and Opioids | Research

The takeaway

Among 22,763 cancer patients, cannabis dependence showed no significant association with mortality, while alcohol and opioid dependence were linked to significantly higher death rates even after adjusting for tumor stage.

Cancer patients using cannabis, oncologists, addiction medicine specialists

Cannabis dependence not linked to cancer mortality

What the researchers found

Cannabis dependence was not significantly associated with mortality among cancer patients. In contrast, alcohol and opioid dependence remained significant predictors of mortality after adjusting for tumor stage. Tobacco dependence showed an attenuated association after stage adjustment, suggesting confounding by later-stage diagnosis.

Why it matters

Cancer patients sometimes worry that cannabis use might worsen their prognosis. This large study suggests cannabis dependence, unlike alcohol or opioid dependence, does not appear to independently increase mortality risk in cancer patients.

The numbers in context

22,763 cancer patients; cannabis dependence not significant for mortality; alcohol and opioid dependence significant in adjusted models; tumor stage adjustment reduced opioid and tobacco hazard ratios.

How the study worked

Retrospective analysis of 22,763 cancer patients aged 18+ from UC San Diego Health. Substance dependence identified from electronic health records. Cox proportional hazards models adjusted for tumor staging (TNM system with imputed missing data).

What this study cannot tell us

Substance dependence from clinical notes may undercount actual use. Small sample of cannabis-dependent patients limits power. Single health system. Cannot distinguish between types/amounts of cannabis use. Observational design with potential unmeasured confounders.

How to read the evidence

Large retrospective cohort with tumor stage adjustment, but limited by small cannabis-dependent sample and observational design.

When this study was published

2025 publication

The bigger picture

As more cancer patients use cannabis for symptom management, understanding whether it affects survival is critical. This study adds to evidence suggesting cannabis does not worsen cancer outcomes, though the small number of cannabis-dependent patients limits statistical power.

Questions still open

Would a larger sample of cannabis-dependent cancer patients reveal a mortality signal?
Does cannabis type or consumption method matter for cancer outcomes?

Common questions

Does cannabis use affect cancer survival?

In this study of 22,763 cancer patients, cannabis dependence was not significantly associated with mortality. However, the small number of cannabis-dependent patients means this finding should be interpreted cautiously.

Which substances are linked to worse cancer outcomes?

Alcohol and opioid dependence were significantly associated with higher cancer mortality even after accounting for tumor stage. Cannabis and amphetamine dependence were not, though both had limited sample sizes.

Read the original research

Influence of Substance Use Disorders on Mortality in a Systemwide Cohort of Cancer Patients.

Psycho-oncology, 34(8), e70243

View on PubMed ↗Publisher’s paper ↗

Citation

Khoyilar, Shawnly; Purushothaman, Vidya; Cuomo, Raphael E. (2025). Influence of Substance Use Disorders on Mortality in a Systemwide Cohort of Cancer Patients.. Psycho-oncology, 34(8), e70243. https://doi.org/10.1002/pon.70243