Cannabis and Cannabinoids Alter the Gut Microbiome with Both Beneficial and Harmful Effects | Research

The takeaway

A systematic review of 9 studies found cannabis and cannabinoids affect the human microbiome across multiple body sites, with positive associations including reduced inflammatory bacteria and negative effects including decreased microbial diversity with heavy use.

microbiome researchers, gastroenterologists, infectious disease specialists, cannabis researchers

What the researchers found

Nine studies (2 clinical trials, 7 observational) examined cannabis/cannabinoid effects on oral, GI, fecal, and vaginal microbiota. Positive associations: serum endocannabinoids correlated with beneficial gut microbiota via elevated SCFAs and anti-inflammatory actions. In HIV patients, marijuana use reduced pro-inflammatory Prevotella. Negative associations: excessive consumption reduced microbial richness and diversity with increased systemic inflammation.

Why it matters

The microbiome is increasingly recognized as central to health and disease. Understanding how cannabis affects it is essential for evaluating the full impact of cannabis use and developing microbiome-based therapeutic strategies.

The numbers in context

9 studies identified: 2 clinical trials, 7 observational. Body sites: oral, GI, fecal, vaginal. Contexts: cognitive deficiency, depression, HIV, inflammation/pain, oral disease, obesity. Both alpha diversity changes and specific bacterial abundance shifts documented.

How the study worked

Systematic review searching PubMed, Embase, and Cochrane Library CENTRAL. Included studies on marijuana, medical cannabis, cannabinoids, and cannabinoid-like lipid mediators across all clinical conditions and body sites.

What this study cannot tell us

Very small evidence base (9 studies). Heterogeneous clinical contexts, cannabis products, and microbiome assessment methods. Cannot determine causation in observational studies. Different body sites make cross-study comparison difficult.

How to read the evidence

Systematic review methodology is sound, but the extremely small evidence base (9 studies) and heterogeneous contexts severely limit conclusions.

When this study was published

2025 publication.

The bigger picture

The dual nature of cannabis-microbiome interactions — beneficial at moderate levels but potentially harmful with heavy use — mirrors the dose-dependent pattern seen in many cannabis health outcomes. This adds the microbiome as another dimension to consider in cannabis risk-benefit assessments.

Questions still open

Is the microbiome a mediator of cannabis health effects?
Could microbiome testing guide personalized cannabis therapy?

Common questions

Does cannabis affect gut bacteria?

This systematic review found cannabis and cannabinoids do affect the microbiome — both positively (increasing anti-inflammatory bacteria, elevating beneficial short-chain fatty acids) and negatively (reducing diversity with heavy use, increasing systemic inflammation). Effects depend on dose and clinical context.

Is cannabis good or bad for the microbiome?

Both. This review found moderate use and endocannabinoid signaling had positive associations with gut health, while excessive consumption reduced microbial diversity and increased inflammation. The relationship appears dose-dependent.

Read the original research

Cannabis and cannabinoid-microbiome interactions in varied clinical contexts: A comprehensive systematic review.

Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, 182, 117764

View on PubMed ↗Publisher’s paper ↗

Citation

Thu, May Soe; Campbell, Barry J; Hirankarn, Nattiya; Nopsopon, Tanawin; Ondee, Thunnicha; Hall, Szaye Rawicha; Jagota, Ananya; Fothergill, Joanne L; Pongpirul, Krit. (2025). Cannabis and cannabinoid-microbiome interactions in varied clinical contexts: A comprehensive systematic review.. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, 182, 117764. https://doi.org/10.1016/j.biopha.2024.117764