With that in mind, scientists at the University of Arizona recently conducted a study in which a group of 18 autistic children received fecal transplants from donors with healthy gastrointestinal systems. Not only did the procedure help to "rebalance" their gut flora, but it also improved their behaviour.

First of all, a fecal transplant is just what it sounds like. Feces from one person are screened for disease-causing organisms, and then introduced into the recipient's digestive tract. In this case, the recipients first took antibiotics for two weeks, to wipe out their existing gut flora. They then received the fecal transplant initially in a high-dose liquid form, after which it was delivered in a lower-dose powder mixed into smoothies.

Such transplants have worked in the past for other people with gastrointestinal problems, and they did so in this case, too. In the eight weeks following the end of the treatment, parents reported a substantial decrease in their children's bouts of gut problems such as diarrhea and stomach pain.

Interestingly, though, they also observed substantial improvements in their behaviour. Using questionnaires designed to assess social skills, irritability, hyperactivity, communication and other factors, it was found that the average developmental age of the children (aged 7 to 16 years) increased by an average of 1.4 years.