If you’ve seen online that people with ADHD have a different gut microbiome, but you’re not exactly sure how it’s different, we’re here to break down the current research. To learn more about what the ADHD gut-brain connection is, check out this article.
Everything we currently know about the ADHD gut microbiome
A 2025 meta-analysis reviewed all studies done on ADHD and the gut and found that some bacteria showed both increases and decreases across different studies. Bifidobacterium, Lactobacillus, Prevotella, and Ruminococcus, for example, were inconsistent, with some studies having increases and some studies showing decreases. That said, the meta-analysis found a few consistent patterns:
- Consistently increased: Odoribacter, Eggerthella, Agathobacter, Phascolarctobacterium
- Consistently decreased: Faecalibacterium, Eubacterium eligens, Ruminococcus
- Combined-type ADHD showed more distinct gut changes than the other subtypes
Okay, now what does all this mean?
| Increased | |||
| Odoribacter | Agathobacter | Phascolarctobacterium | Eggerthella |
| – Important for turning fiber into short-chain fatty acids (SCFAs) like butyrate and acetate. – Higher odoribacter may be reflective of either a low-fiber diet or a body that has a difficult time metabolizing carbohydrates (therefore requiring more odoribacter) | – Important for turning fiber into short-chain fatty acids (SCFAs) like butyrate. – Higher agathobacter may be reflective of either a low-fiber diet or a body that has a difficult time metabolizing carbohydrates (therefore requiring more agathobacter). – Higher agathobacter may also be reflective of a high-fiber diet. – Higher levels are associated with protection against Alhzeimers | – Important for using carbohydrates and turning them into energy. – Higher phascolarctobacterium is typically reflective of reduced inflammation and improved glucose metabolism. – Higher phascolarctobacterium may also be reflective of exaggerated immune system or insulin responses (therefore requiring more phascolarctobacterium) | – Linked to chronic inflammation and gut issues |
| Decreased | |||
| Faecalibacterium | Eubacterium eligens | Ruminococcus | |
| – Important to break down resistant starches into food for the above bacteria. – Lower ruminococcus (especially Ruminococcus bromii) is associated with reduced butyrate production and increased inflammation. – Lower levels may be indicative of a low-fiber diet | – An important bacterium for butyrate and acetate production. – Lower Eubacterium eligens is reflective of lower butyrate and acetate production and increased inflammation | – Important to break down resistant starches into food for the above bacteria. – Lower ruminococcus (especially Ruminococcus bromii) is associated with reduced butyrate production and increased inflammation. – Lower levels may be indicative of a low-fiber diet | |
So, what does all this mean if you have ADHD?
While we don’t yet have a single, clear gut bacteria “signature” for ADHD, the patterns we see point toward something important: People with ADHD tend not to eat enough resistant starch and fiber (or our bodies may be working harder to process them), and our bodies may be more prone to inflammation.
Increased levels of bacteria like Odoribacter, Eggerthella, and Agathobacter suggest shifts in how energy and inflammation are managed in the body. Meanwhile, the consistent decrease in butyrate-producing bacteria like Faecalibacterium and Eubacterium eligens points to a gut environment that may have trouble supporting calm, focused brain states.
This doesn’t mean your gut is broken if you have ADHD, but it does mean your microbiome might benefit from a little extra support. Whether through diet, lifestyle, or targeted interventions, there is a growing body of research that says what’s happening in your gut is likely influencing what’s happening in your brain.
For some tangible steps you can take today, check out 6 Easy Food Strategies to Support Your ADHD Gut Microbiome. We’ve also got you covered if you’re curious about probiotic supplements—no affiliate links included, only the research!
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