Gut Microbiome Testing
Stool-based sequencing — 16S rRNA or shotgun metagenomics — profiling bacterial composition and usually reported back as a diversity score or a list of “good” and “bad” bacteria. The underlying science is real: the gut microbiome genuinely influences metabolism, immune function and possibly mood through the gut-brain axis, and it is an active, legitimate research field. The commercial test is a different object from the research.
An international consensus statement on microbiome testing in clinical practice, published in The Lancet Gastroenterology & Hepatology in 2024, concluded that evidence supporting the clinical usefulness of microbiome diagnostics is scarce, and that commercial providers offer direct-to-consumer tests without regulatory approval or consensus on their value — risking wasted patient resources. A related 2025 analytical study found major discrepancies between different commercial providers testing the same stool sample, with inter-provider variability on the same scale as the biological variability between different people. No stool microbiome test can currently diagnose depression, anxiety or neurodevelopmental disorders in clinical practice, and there are no regulatory-approved clinical microbiome diagnostics as of this review.
International consensus statement on microbiome testing in clinical practice. Lancet Gastroenterol Hepatol. 2024. PubMed: PMID 39647502