Research Review: Autism and the Gut Microbiome

March 28, 2017
By: Janie Jacoby

autismandthegutbiome.jpgIf you follow health and nutrition, it can be hard to walk out the door these days without running into a new revelation about the gut microbiome. The more we look, the more connections we find between our microbes and every facet of health, from our bones to our brains.

A study published in early 2017 investigates one of the newest microbiome interventions: fecal microbiota transplant (FMT) for children with autism spectrum disorders (ASD). Let’s take a closer look.

Fecal Microbiota Transplant

First things first: FMT is a therapy in which processed fecal matter from healthy donors is transplanted into the GI tracts of sick patients. The goal is to replace a dysfunctional gut microbiome with a healthy one. At this time, it is FDA-approved only for the treatment of recurrent c. difficile infection, and doctors must apply for a permit to use it in other situations. FMT is being studied for a variety of digestive and immune disorders, such as irritable bowel syndrome and inflammatory bowel disease.

How does this relate to autism? As it turns out, alterations to the microbiome, digestive disorders, and immune dysregulation are hallmarks of ASD.

The Complex Causes of Autism Spectrum Disorders

ASD is defined not by any common cause, but by symptoms: impaired social communication and restricted, repetitive behaviors and interests.These symptoms are caused by a variety interrelated of factors, which vary for each person:

A recent article illustrated one view of their complex relationships. As you can see below, there are many possible paths to ASD symptoms. For example, genetic and environmental factors can directly lead to symptoms, or they can work indirectly, through gut dysfunction and dysbiosis. There is not a direct chain of cause and effect: dysbiosis can cause immune dysregulation, or immune dysregulation can cause dysbiosis.


© Vuong H, Hsiao E. Emerging Roles for the Gut Microbiome in Autism Spectrum Disorder. Biological Psychiatry. 2016.

Pilot Study

Now that we have taken a closer look at FMT and ASD, let’s return to the recent study. In this study, 18 children with ASD had two weeks of antibiotics, a bowel cleanse, and then 8 weeks of FMT treatments. Stool samples were collected throughout the process, and compared to samples from children without ASD. Gastrointestinal (GI) symptoms and ASD symptoms were tracked.

They found that GI symptoms improved by 80% on average, and only two participants did not improve by at least 50%. ASD symptoms improved as well, as measured by 5 different assessment tools. For example, there was a 22% reduction in scores on one test of core ASD symptoms, and another test showed a 1.4 year increase in developmental age. They also found that the GI and ASD symptoms were related: worse GI symptoms were associated with worse ASD symptoms.

The FMT was effective at restoring microbial diversity and abundance, and at the end of the study the participants’ microbiomes were similar to the control group. The microbiome changes and the improvements in GI and ASD symptoms lasted through the end of the study: 8 weeks after the treatment ended.

This was a pilot study, and thus was not blinded or placebo-controlled, which is a limitation. However, it did demonstrate that the treatment is safe, tolerable, and potentially effective. The research group is now planning a larger randomized, double-blind, placebo-controlled trial as a follow up. I look forward to seeing the results of future studies.

Moving Forward

ASD is incredibly complex, and there is not an easy cure on the horizon. Yet, it is exciting that our understanding of autism spectrum disorders is growing, and that this could lead to new, targeted treatments.