Families were recruited through university and central hospitals. Detailed clinical and medical examinations were performed by experienced child neurologists as described elsewhere40. Diagnoses were based on ICD-10 39 and DSM-IV 41 diagnostic nomenclatures. Families with known associated medical conditions or chromosomal abnormalities were excluded from the study. A total of 106 families included 400 individuals for whom genotype data was available. Of these, 111 had a diagnosis of infantile autism and 13 a diagnosis of Asperger syndrome. All families were Finnish, except for one family where the father was Turkish.
