“Genetic Factors The possible contribution of genetic factors to autism as “inborn autistic disturbances of affective contact” (Kanner, 1943) is now confirmed. Family studies show that the disorder is more frequent in families with autistic probands (Ritvo et al., 1989), and the autistic phenotype is also less variable in relatives (Spiker et al., 1994). The detected risk of recurrence is approximately 75 times higher between sibs than in the general population (Bolton et al., 1994). Evidence for genetic predisposition to autism also comes from twin studies. Folstein and Rutter (1997) showed different concordance rates between monozygotic (MZ) and dizygotic (DZ) twins, and found that in most sib pairs discordant for autism, the disorder was caused by brain injuries. Bailey et al. (1995) confirmed these data and showed 92 percent concordance for social and cognitive abnormalities in MZ twins and 10 percent concordance in DZ twins. Studies of twins performed by Pickles et al. (1995) and Greenberg et al. (2001) also provide evidence for a genetic basis of autism. The heritability of autism is estimated as 90 percent (Szatmari et al., 1998)."
Bauman, Margaret L.(Editor). Neurobiology of Autism. Baltimore, MD, USA: The Johns Hopkins University Press, 2004. p 218.
"Say what you will about the sweet miracle of unquestioning faith, I consider a capacity for it terrifying and absolutely vile!" Kurt Vonnegut