I have just read a chapter on gut health in Prof Tim Spector's new book Spoon Fed (which is full of eye opening information). Current consensus is that there is a big link between gut health and mental health with the gut being responsible for the production or serotonin and other mood related chemicals that the body produces. The book does briefly mention autism because many with ASD also have IBS and other related issues. As ever this is not true for everyone but if we all sorted out gut out a bit more then there would be less depression and anxiety and we would need a lot fewer drugs.