Could autism be treated with probiotics? In a new study from California Institute of Technology (Caltech), researchers show that probiotic therapy reduces cognitive symptoms in lab mice afflicted with the disorder. The findings could transform palliative care for the complex and often debilitating condition that currently occurs in about one percent of children.

While autism spectrum disorders (ASD) typically manifest as a set of cognitive limitations and social disabilities, many cases are also associated with stomach aches, constipation, and other gastrointestinal (GI) issues. Given the fact that previous research efforts have linked gut bacteria to behavior, this co-occurrence has fueled speculations that the two sets of symptoms are somehow related to each other. "Traditional research has studied autism as a genetic disorder and a disorder of the brain, but our work shows that gut bacteria may contribute to ASD-like symptoms in ways that were previously unappreciated," Sarkis K. Mazmanian, a professor of biology at Caltech, explained in a press release. "Gut physiology appears to have effects on what are currently presumed to be brain functions."

The new study, which is published in the journal Cell, sought to determine whether changes to this bacterial flora can influence autism-like behavior. To do this, the researchers used a mouse model designed to emulate the social and emotional restrictions typically associated with the disorder. The team treated the subjects with a probiotic therapy involving Bacteroides fragilis — a bacterium that has previously been used in other animal models of GI.

Intriguingly, the probiotic therapy appeared to alleviate the subjects’ gut problems as well as their behavioral symptoms. The treatment group became more social, less anxious, and less likely to engage in repetitive behavior such as obsessive digging. "The B. fragilis treatment alleviates GI problems in the mouse model and also improves some of the main behavioral symptoms," said lead author Elaine Hsao. "This suggests that GI problems could contribute to particular symptoms in neurodevelopmental disorders."

That said, more research is needed to transcend some of the study’s current limitations. For example, while autism in humans is thought to be the result of environmental factors in combination with biological factors, the researchers’ mouse model was derived exclusively from environmental factors — namely, a maternal immune response brought on by viral infection during pregnancy. Still, the team is confident that their discovery will ultimately be adapted for human use.

"This probiotic treatment is postnatal, which means that the mother has already experienced the immune challenge, and, as a result, the growing fetuses have already started down a different developmental path," senior author Paul H. Patterson explained. "In this study, we can provide a treatment after the offspring have been born that can help improve certain behaviors. I think that's a powerful part of the story."