As late as the mid-1970s there was little evidence of a genetic role in<unk> ; evidence from genetic epidemiology studies now suggests that it is one of the most heritable of all psychiatric conditions. The first studies of twins estimated heritability to be more than 90%; in other words, that genetics explains more than 90% of<unk>  cases. When only one identical twin is<unk> ic, the other often has learning or social disabilities. For adult siblings, the risk of having one or more features of the broader<unk>  phenotype might be as high as 30%, much higher than the risk in controls. About 10–15% of<unk>  cases have an identifiable Mendelian (single-gene) condition, chromosome abnormality, or other genetic syndrome, and ASD is associated with several genetic disorders. Since heritability is less than 100% and symptoms vary markedly among identical twins with<unk> , environmental factors are most likely a significant cause as well. If some of the risk is due to gene-environment interaction the 90% heritability may be too high; However, in 2017, the largest study, including over three million participants, estimated the heritability at 83%. Genetic linkage analysis has been inconclusive; many association analyses have had inadequate power. Studies have examined more than 100 candidate genes; many genes must be examined because more than a third of genes are expressed in the brain and there are few clues on which are relevant to<unk> .
Epidemiology of autism
Genetics of post-traumatic stress disorder
Epidemiology of attention deficit hyperactive disorder
Epidemiology of schizophrenia
Prognosis of schizophrenia
Mechanism of autism
Epidemiology of child psychiatric disorders
Psychiatric genetics