Few questions in the FMT field generate more interest — or more confusion — than whether Fecal Microbiota Transplantation can help children with Autism Spectrum Disorder (ASD). Families reach out to our clinic regularly after reading headlines about microbiome research and autism. I want to walk through what the published evidence actually shows, what it doesn't show, and how I think about this clinically.
Why Researchers Are Studying the Gut in Autism
Up to 70% of children with ASD experience chronic gastrointestinal symptoms — constipation, diarrhea, abdominal pain, and reflux — at rates dramatically higher than the general pediatric population. Multiple studies have also documented measurable differences in gut microbiome composition between children with autism and neurotypical controls, including reduced microbial diversity, lower levels of beneficial species like Bifidobacterium and Prevotella, and altered short-chain fatty acid profiles.
These findings, combined with growing recognition of the gut-brain axis as a real, mechanistic communication system, have driven interest in whether modifying the microbiome could improve both GI symptoms and behavioral measures in ASD.
The Arizona State University Studies
The most cited research on FMT for autism comes from Dr. James Adams and colleagues at Arizona State University, who developed a modified protocol called Microbiota Transfer Therapy (MTT). Their 2017 open-label study, published in Microbiome, treated 18 children with ASD and chronic GI symptoms with a two-week vancomycin pretreatment followed by an extended course of FMT.
The results were striking: an 80% reduction in GI symptoms that persisted at the eight-week endpoint, along with significant improvements on standardized behavioral assessments including the Childhood Autism Rating Scale (CARS) and the Social Responsiveness Scale (SRS). A 2019 follow-up published in Scientific Reports reported that two years after treatment, GI improvements were maintained and ASD symptom severity had continued to decrease.
These outcomes generated significant excitement, and rightly so. But it's important to be honest about the limitations: the original study was open-label (not blinded, no placebo control), the sample size was small, and the modified protocol used in these trials differs substantially from standard FMT.
What the Evidence Doesn't Yet Establish
As of this writing, there is no large randomized, placebo-controlled trial of FMT for ASD that has been published and peer-reviewed. The pediatric clinical trials that would establish FMT as a proven treatment for autism are ongoing but not complete. The FDA has not approved FMT for autism, and any use for this indication is investigational.
We also don't yet know which children are most likely to respond, what the optimal protocol is, how long benefits last beyond two years, or whether the behavioral improvements documented in the open-label trials would hold up under blinded conditions. These are real, open scientific questions.
How I Think About This Clinically
At our clinic, we don't position FMT as a treatment for autism itself. What we do recognize is that many children with ASD have severe, chronic GI symptoms that significantly affect quality of life, and that microbiome restoration through FMT has well-established benefit for certain gut conditions — most notably C. difficile infection, where the evidence is overwhelming.
Families who reach out to us are typically focused on GI symptoms first, with hope that addressing the gut may also support behavioral and developmental outcomes. We're transparent that the GI evidence is much stronger than the behavioral evidence, and we structure our consultations accordingly. We also work closely with pediatric specialists and only proceed when there's a clear clinical indication.
Questions to Ask Any Clinic
If you're researching FMT for a child with autism, I'd encourage you to ask any clinic the following: What specific protocol do you use, and how does it compare to the published research? How are donors screened? What outcomes do you measure, and how are families followed long-term? Are there any conflicts of interest that might affect the recommendations you receive?
These are reasonable questions, and any reputable program should answer them clearly. You can also review our overview of what to look for in an FMT provider and our guide to how to access FMT treatment. If you'd like to discuss your child's specific situation, schedule a consultation and we'll review the case honestly.
