“Infantile Autism: A Genetic Study Of 21 Twin Pairs”, 1977-09-01 (; similar):
A systematic study was made of a representative group of 21 same-sexed twin pairs (11 MZ and 10 DZ) in which at least one twin showed the syndrome of infantile autism.
There was a 36% pair-wise concordance rate for autism in MZ pairs compared with 0% concordance in DZ pairs. The concordance for cognitive abnormalities was 82% in MZ pairs and 10% in DZ pairs. It was concluded that there were important hereditary influences concerning a cognitive deficit which included but was not restricted to autism. In 12⁄17 pairs discordant for autism, the presence of autism was associated with a biological hazard liable to cause brain damage.
It was concluded that brain injury in the infancy period may lead to autism on its own or in combination with a genetic predisposition. Uncertainty remains on both the mode of inheritance and exactly what is inherited.