In recent years schizophrenia has been assumed to be largely a genetic disease with heritability estimates, derived primarily from family and twin studies, of 80%-85%. However, the results of genetic research on schizophrenia have not yielded results consistent with that estimate of heritability. In particular, extensive genetic studies have not led to new methods for diagnosis and treatment. An examination of the twin studies on which heritability is based shows why such studies exaggerate the genetic component of schizophrenia. In addition, the effects of infectious agents such as Toxoplasma gondii and the composition of the microbiome can produce a clinical picture that would also appear to be largely genetic due to familial aggregation and a role for a partial genetic contribution to the immune system. It is concluded that the genetic component of schizophrenia may have been overestimated and an increased focus on gene-environmental interactions is likely to accelerate research progress on this disease.
Keywords: Heritability; Microbiome; Toxoplasmosis; Twin studies.
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Heritability of Schizophrenia and Schizophrenia Spectrum Based on the Nationwide Danish Twin RegisterR Hilker et al. Biol Psychiatry 83 (6), 492-498. PMID 28987712.The key strength of this study is the application of a novel statistical method accounting for censoring in the follow-up period to a nationwide twin sample. The estimate …
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Heritability of Neuropsychological Measures in Schizophrenia and Nonpsychiatric Populations: A Systematic Review and Meta-analysisGAM Blokland et al. Schizophr Bull 43 (4), 788-800. PMID 27872257. - ReviewSchizophrenia is characterized by neuropsychological deficits across many cognitive domains. Cognitive phenotypes with high heritability and genetic overlap with schizoph …
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Familial Aggregation and Heritability of Schizophrenia and Co-aggregation of Psychiatric Illnesses in Affected FamiliesIJ Chou et al. Schizophr Bull 43 (5), 1070-1078. PMID 27872260.Strong familial aggregation of schizophrenia has been reported but there is uncertainty concerning the degree of genetic contribution to the phenotypic variance of the di …
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