Boys with regressive autism have larger brains than their healthy counterparts at age three, new research has shown. Although previous research has indicated brain size differences in those with the condition, this study, published in Proceedings of the National Academy of Sciences, shows differences to those children with early onset autism. Early onset autism preschoolers studied by the University of California scientists did not share the same brain characteristics as those with regressive autism. Lead researcher David Amaral explained: "The purpose of defining different types of autism is to more effectively study the cause of each type and eventually determine effective preventative measures and better, individualised treatments." Brain volume in three-year-old males with regressive autism was six per cent greater than age-matched peers. Twenty-two per cent of those with regressive autism were found to have enlarged brains, compared to just five per cent of boys without the condition. In November, US researchers found wide variation in autism diagnosis across different clinics, suggesting clinical diagnostic techniques are not being applied consistently. Find out about Barchester's support for adults and children with a wide range of Autistic spectrum conditions.