There is some new evidence that implies that autism is caused by a lack of gut bacteria. two recent studies, the first conducted using humans and one on laboratory rodents. The study using humans was prompted by an earlier study that found some children with autism were missing hundreds of the thousand-plus bacterial species that can be found in a non-autistic person. For the second study, researchers collected bacteria from the faeces of both autistic and non-autistic people and transplanted these into mice. They then interbred the mice and studied the offspring. Most of the young mice with the gut bacteria from autistic human participants showed features of autism. Click here to read more.