Two years after the transplant, a professional evaluator found a 45% reduction in core autism disorder symptoms  (ASD) such as language, social interaction, and behavior, raising new hopes for potential treatments.

“We are finding a very strong connection between the microbes that live in our intestines and signals that travel to the brain,” said Krajmalnik-Brown, a professor at the Biodesign Swette Center for Environmental Biotechnology at the Biodesign Institute and ASU’s School for Sustainable Engineering and the Built Environment. “Two years later, the children are doing even better, which is amazing.”

According to the CDC, about 1 in 59 children in the US is diagnosed with autism — “about half a million people on the autism spectrum will become adults over the next decade, a swelling tide for which the country is unprepared,” a CDC report notes.

Autism spectrum disorder is also very difficult to treat, which has spurred researchers to look for more innovative approaches. There are no medications that can cure ASD or eliminate the core symptoms. However, some medications can reduce some symptoms, and behavioral therapy and social therapy have also shown some promise. But in a new study, Krajmalnik-Brown and colleagues tried something else.

They started from a curious observation: autism and gastrointestinal problems seem to be strangely connected in some cases.

“Many kids with autism have gastrointestinal problems, and some studies, including ours, have found that those children also have worse autism-related symptoms,” said Krajmalnik-Brown. “In many cases, when you are able to treat those gastrointestinal problems, their behavior improves.”

So they set out to see if, by addressing gastrointestinal issues, they can also address autism symptoms. They opted for an innovative approach developed by Dr. Thomas Borody, an Australian gastroenterologist. The approach is called Microbiota Transfer Therapy (MTT), and it’s essentially a special type of fecal transplant. MTT is already showing benefits, especially in regards to treating  Clostridioides difficile infection.

The idea is pretty straightforward: people suffering from this infection have a damaged gut microbiome. If this microbiome can be restored, they can fight off the infection more effectively — and the benefits seem to extend to other intestinal problems as well. So the team used MTT to see if, indirectly, it can have an effect on autism syndrome. It did.

The treatment was applied to 18 patients (children), first showing substantial gut improvement — and two years post-treatment, most of the initial improvements remained. But something even more exciting happened: over the next two years, parents started reporting a steady reduction in autism syndrome symptoms. A professional evaluator found a 45% reduction in core ASD symptoms (language, social interaction, and behavior) at two years post-treatment compared to before treatment began. In other words, the improvements in terms of ASD symptoms also seem to be long-lasting.

This is especially promising as 30-50% of people with autism have some form of chronic gastrointestinal problems, most notably constipation or diarrhea. The chronic discomfort and pain can make sufferers more irritable and decrease their attention and learning power, negatively impacting behavior.

The fecal transplant study fits well with previous research, which found that only vancomycin (an antibiotic) had produced major temporary improvements in GI and autism symptoms — although the benefits were lost a few weeks after treatment stopped.

The question now is what’s going on in kids’ intestines, and how could it be improved in the long term?

A lack of healthy bacteria seems like the most likely problem.

 “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.

“Understanding which microbes and chemicals produced by the microbes are driving these behavioral changes is at the heart of our work,” Krajmalnik-Brown said.

Another hint as to what was going on was how the symptoms evolved through time. It’s very unusual to see gradual improvement after the treatment stopped, which also seems to suggest that after the first transplant, it was a gradual transformation to a healthy microbiome. Also telling is the fact that many of the participants in the trial shared common traits such as birth by C-section, reduced breastfeeding, increased antibiotic, and low fiber intake — all of which are linked to gut bacteria deficiencies. It’s still a small trial and a “smoking gun” is missing, but all the evidence seems to point in the direction of microbiome health being the main problem.

The team is now working on optimizing and improving the treatment to improve benefits even more. They are also considering trying out a booster dose to see if it can help in some cases.

The study was published in Nature.