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Psychiatry Res. 2019 Aug;278:146-150. doi: 10.1016/j.psychres.2019.06.006. Epub 2019 Jun 4.

Schizophrenia as a pseudogenetic disease: A call for more gene-environmental studies.

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Stanley Medical Research Institute, 301-571-2078, 10605 Concord St, Suite 206, Kensington, MD20895, USA. Electronic address:
Stanley Laboratory of Developmental Neurovirology, Johns Hopkins Medical Center, Baltimore, MD, USA.


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.


Heritability; Microbiome; Toxoplasmosis; Twin studies

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