Autism and Twin Studies (1)

Recent research into the causes of autism suggests that the disorder is predominantly genetically determined.

Recent research into the causes of autism suggests that the disorder is predominantly genetically determined.

A 1995 study of autism in a British sample compared the rates of autism in monozygotic (identical) and dizygotic (fraternal) twins. The study found that for monozygotic (identical) twins, if one twin met the criteria for autism, then 60% of the time the other twin also met this criteria. For monozygotic twins, therefore, the concordance rate for autism was found to be 60%. By comparison, the concordance rate for dizygotic twins was 0%. Because monozygotic twins share all genes and dizygotic twins share on average 50% of their genetic information, this provides compelling evidence that autism is indeed predominantly genetically determined.