Below is an excerpt from article about some recent and preliminary explorations of the relationship between autism and human microbiome:
"His parents reluctantly began to accept that his gut problems might simply be yet another manifestation of his autism. “We kind of gave up,” says Sharon, Sam’s mother. (Their names have been changed to protect their privacy.)
Unfortunately, Sam’s experience is common among children with autism. About 40 to 60 percent of these children cope with gastrointestinal (GI) problems
Despite their pain, these children’s abdominal tracts generally appear normal, says Emeran Mayer
It’s also possible that the real culprit of these digestive symptoms is not human at all. Evidence from the past decade suggests that GI problems in some people with autism stem from disruptions in the gut microbiome—the complex stew of bacteria and other microbes that help to digest food, make vitamins, and protect against pathogens. Scientists have found tantalizing clues that the types of microbes that live in the guts of people with autism differ from those in people without the condition.
So far, this research poses more questions than it answers, but the need for clarity is urgent: Against the advice of experts, and in a desperate attempt to help their pain-wracked children, some parents are performing do-it-yourself fecal transplants, overhauling the gut microbiome by transferring stool (and the intestinal bacteria it contains) from a healthy donor into a child with autism."
For the rest of this article, with links to other research and sources see:
http://www.theatlantic.com/health/archive/2015/11/how-microbes-shape-autism/416220/