The UCLA Registry for Genetic Studies in Autism was established in 1980
to test the hypothesis that genetic factors may be etiologically
significant in subsets of patients. To date 61 pairs of twins have enrolled
and 40 meet research diagnostic criteria for autism. The authors found a
concordance for autism in these 40 pairs of 95.7% in the monozygotic twins
(22 of 23) and 23.5% in the dizygotic twins (four of 17).