Does cannabis affect the gut microbiome?

The gut microbiome and the ECS are bidirectionally connected — the gut microbiome influences endocannabinoid tone, and cannabinoids affect gut microbial composition. This "microbiome-ECS axis" is an emerging research area. Animal evidence: THC altered gut microbiome composition in mice, increasing Lactobacillus and Porphyromonadaceae while reducing Firmicutes — changes associated with reduced obesity and inflammation. CBD also altered microbiome composition in animal models of colitis, increasing beneficial bacteria. Human evidence: a 2020 study found cannabis users had distinct gut microbiome profiles compared to non-users, with higher Prevotella (associated with anti-inflammatory effects) and lower Bacteroides. However, causality is unclear — diet, lifestyle, and other factors differ between cannabis users and non-users. The microbiome-ECS connection may partly explain cannabis effects on appetite, weight, and gut inflammation. This is a genuinely exciting research frontier but human clinical evidence is preliminary.