GeneticEstimates of heritability va

Genetic

Estimates of heritability vary because of the difficulty in separating the effects of genetics and the environment;[28] averages of 0.80 have been given.[29] The greatest risk for developing schizophrenia is having a first-degree relative with the disease (risk is 6.5%); more than 40% of monozygotic twins of those with schizophrenia are also affected.[1] If one parent is affected the risk is about 13% and if both are affected the risk is nearly 50%.[29]

It is likely that many genes are involved, each of small effect and unknown transmission and expression.[1] Many possible candidates have been proposed, including specific copy number variations, NOTCH4, and histone protein loci.[30] A number of genome-wide associations such as zinc finger protein 804Ahave also been linked.[31] There appears to be overlap in the genetics of schizophrenia andbipolar disorder.[32] Evidence is emerging that the genetic architecture of schizophrenia involved both common and rare risk variation.[33]

Assuming a hereditary basis, one question from evolutionary psychology is why genes that increase the likelihood of psychosis evolved, assuming the condition would have been maladaptive from an evolutionary point of view. One idea is that genes are involved in the evolution of language and human nature, but to date such ideas remain little more than hypothetical in nature