Scientific research continues to uncover interesting connections between the gut microbiome and human health, including everything from depression to PTSD to autoimmune disease. Another example of this are emerging ties between gut health and autism. Exciting new research, now moving to Phase 3 human trials, has found boosting microbial diversity via fecal transplants can dramatically reduce autism symptoms in the long term.
Editor's note: Readers often ask us for follow-ups on memorable stories. What has happened to this story over the years? This article was originally published in 2019 but it has been re-edited and updated with new information current as of April 7, 2025. Enjoy!
One in every 59 children born in the US is diagnosed with autism, according to the Centers for Disease Control and Prevention, and unfortunately for many of them, chronic gastrointestinal issues are a harsh reality of their condition. According to scientists at Arizona State University (ASU), who conducted the new study, around 30 to 50% of autism sufferers experience serious gut problems like constipation, diarrhea and stomach pain.
"Many kids with autism have gastrointestinal problems, and some studies, including ours, have found that those children also have worse autism-related symptoms," ASU's Rosa Krajmalnik-Brown said back in 2019 during the early stages of the work. "In many cases, when you are able to treat those gastrointestinal problems, their behavior improves."
A key study in 2019 built on earlier research from 2017 that found introducing new bacteria via fecal transplants in 18 autistic children brought about marked improvements in their behavior, as measured through questionnaires assessing their social skills, hyperactivity, communication and other factors.
These improvements held for eight weeks, an impressive outcome to be sure. But the Arizona State University researchers then set out to investigate the enduring effects of the treatment, which involved a bowel cleanse and daily transplants of fecal microbiota over a period of seven to eight weeks. Prior to the treatment, these children all had far lower diversity of gut microbes than those without autism.
"Kids with autism are lacking important beneficial bacteria, and have fewer options in the bacterial menu of important functions that bacteria provide to the gut than typically developing kids," Krajmalnik-Brown said in 2019.
Two years after the treatment, the researchers found that not only did the benefits persist, they seemed to improve. Doctors observations at the eight-week mark found that psychological autism symptoms of the patients had decreased by 24%. But two years later those symptoms had almost been cut in half, with a professional evaluator finding a decrease of 45% in autism symptoms compared to baseline.
Prior to the study, 83% of participants had "severe" autism. Two years later, only 17% were rated as severe, 39% as mild or moderate, and incredibly, 44% were below the cut-off for mild ASD.
"We are finding a very strong connection between the microbes that live in our intestines and signals that travel to the brain," Krajmalnik-Brown said in 2019. "Two years later, the children are doing even better, which is amazing."
The next steps were larger placebo-controlled clinical trial designed to verify their results, with a view to gaining FDA approval for the therapy.
In early 2022 Krajmalnik-Brown and colleagues patented a specific bacterial formulation and spun-off a commercial company called Gut-Brain Axis Therapeutics. The treatment, dubbed Microbiota Transplant Therapy (MTT), moved through a Phase 2 human placebo-controlled trial over the following years and the initial data has been incredibly promising.
"Our phase 2 study for adults with autism found that the treatment group improved more than placebo on the primary outcome (autism symptoms) and on a secondary outcome (daily stool record)," the researchers explain. "Evaluation of symptoms on the Parent Global Impressions found that the treatment group at the end of part 2 improved more than the placebo group in part 1 on nearly all symptoms, with statistically significant improvements in GI, receptive language, and average of all symptoms. There were also marginally significant improvements in tantrums, stimming/perseveration, and cognition."
Now, the team is looking to raise funds to move through the large-scale Phase 3 trials necessary for final FDA approval.
The team's key 2019 study appears in the journal Scientific Reports, and you can hear from the researchers about their most recent findings in the video below.
Source: Arizona State University
An earlier version of this article written by Nick Lavars was published in 2019.
I made an account just to call you out on that. We dint "suffer" from Autism.