In this study patients with Autism and MCDD will be divided in two groups: before and after puberty. Each group will behold 15-40 subjects. They each will be compared with two groups of 20-25 age, sex and IQ matched controls. They will participate in carrying out a MRI scan, filling in some questionnaires and if necessary an IQ test and a general physical examination.The MRI scans will be measured, and compared with each other in order to find ‘disorder-specific’ abnormalities.