Schizophrenia Emerged After Humans Diverged From Neanderthals

Summary: A new study reveals schizophrenia is a modern development that emerged after humans diverged from Neanderthals.

Source: Elsevier.

Schizophrenia poses an evolutionary enigma. The disorder has existed throughout recorded human history and persists despite its severe effects on thought and behavior, and its reduced rates of producing offspring. A new study in Biological Psychiatry may help explain why-comparing genetic information of Neanderthals to modern humans, the researchers found evidence for an association between genetic risk for schizophrenia and markers of human evolution.

“This study suggests that schizophrenia is a modern development, one that emerged after humans diverged from Neanderthals,” said John Krystal, Editor of Biological Psychiatry. “It suggests that early hominids did not have this disorder.”

The cause of schizophrenia remains unknown, but researchers know that genetics play a significant role in the development. According to senior author Ole Andreassen from the University of Oslo in Norway and University of California, San Diego, some think that schizophrenia could be a “side effect” of advantageous gene variants related to the acquisition of human traits, like language and complex cognitive skills, that might have increased our propensity to developing psychoses.

Along with Andreassen, first authors Saurabh Srinivasan and Francesco Bettella, both from the University of Oslo, and colleagues looked to the genome of Neanderthals, the closest relative of early humans, to pinpoint specific regions of the genome that could provide insight on the origin of schizophrenia in evolutionary history.

They analyzed genetic data from recent genome-wide association studies of people with schizophrenia for overlap with Neanderthal genomic information. The analysis tells researchers the likelihood that specific regions of the genome underwent positive selection sometime after the divergence of humans and Neanderthals.

Image shows a woman.
Regions of the human genome associated with schizophrenia, known as risk loci, were more likely to be found in regions that diverge from the Neanderthal genome. NeuroscienceNews.com image is for illustrative purposes only.

Regions of the human genome associated with schizophrenia, known as risk loci, were more likely to be found in regions that diverge from the Neanderthal genome. An additional analysis to pinpoint loci associated with evolutionary markers suggests that several gene variants that have undergone positive selection are related to cognitive processes. Other such gene loci are known to be associated with schizophrenia and have previously been considered for a causal role in the disorder.

“Our findings suggest that schizophrenia vulnerability rose after the divergence of modern humans from Neanderthals,” said Andreassen, “and thus support the hypothesis that schizophrenia is a by-product of the complex evolution of the human brain.”

About this psychology research article

Source: Elsevier
Image Source: This NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Genetic Markers of Human Evolution Are Enriched in Schizophrenia” by Saurabh Srinivasan, Francesco Bettella, Morten Mattingsdal, Yunpeng Wang, Aree Witoelar, Andrew J. Schork, Wesley K. Thompson, Verena Zuber, The Schizophrenia Working Group of the Psychiatric Genomics Consortium, The International Headache Genetics Consortium, Bendik S. Winsvold, John-Anker Zwart, David A. Collier, Rahul S. Desikan, Ingrid Melle, Thomas Werge, Anders M. Dale, Srdjan Djurovic, and Ole A. Andreassen in Biological Psychiatry. Published online August 2016 doi:10.1016/j.biopsych.2015.10.009

Cite This NeuroscienceNews.com Article

[cbtabs][cbtab title=”MLA”]Elsevier. “Schizophrenia Emerged After Humans Diverged From Neanderthals.” NeuroscienceNews. NeuroscienceNews, 15 August 2016.
<https://neurosciencenews.com/schizophrenia-evolution-4845/>.[/cbtab][cbtab title=”APA”]Elsevier. (2016, August 15). Schizophrenia Emerged After Humans Diverged From Neanderthals. NeuroscienceNews. Retrieved August 15, 2016 from https://neurosciencenews.com/schizophrenia-evolution-4845/[/cbtab][cbtab title=”Chicago”]Elsevier. “Schizophrenia Emerged After Humans Diverged From Neanderthals.” https://neurosciencenews.com/schizophrenia-evolution-4845/ (accessed August 15, 2016).[/cbtab][/cbtabs]


Abstract

Genetic Markers of Human Evolution Are Enriched in Schizophrenia

Background
Why schizophrenia has accompanied humans throughout our history despite its negative effect on fitness remains an evolutionary enigma. It is proposed that schizophrenia is a by-product of the complex evolution of the human brain and a compromise for humans’ language, creative thinking, and cognitive abilities.

Methods
We analyzed recent large genome-wide association studies of schizophrenia and a range of other human phenotypes (anthropometric measures, cardiovascular disease risk factors, immune-mediated diseases) using a statistical framework that draws on polygenic architecture and ancillary information on genetic variants. We used information from the evolutionary proxy measure called the Neanderthal selective sweep (NSS) score.

Results

Gene loci associated with schizophrenia are significantly (p = 7.30 × 10−9) more prevalent in genomic regions that are likely to have undergone recent positive selection in humans (i.e., with a low NSS score). Variants in brain-related genes with a low NSS score confer significantly higher susceptibility than variants in other brain-related genes. The enrichment is strongest for schizophrenia, but we cannot rule out enrichment for other phenotypes. The false discovery rate conditional on the evolutionary proxy points to 27 candidate schizophrenia susceptibility loci, 12 of which are associated with schizophrenia and other psychiatric disorders or linked to brain development.

Conclusions
Our results suggest that there is a polygenic overlap between schizophrenia and NSS score, a marker of human evolution, which is in line with the hypothesis that the persistence of schizophrenia is related to the evolutionary process of becoming human.

“Genetic Markers of Human Evolution Are Enriched in Schizophrenia” by Saurabh Srinivasan, Francesco Bettella, Morten Mattingsdal, Yunpeng Wang, Aree Witoelar, Andrew J. Schork, Wesley K. Thompson, Verena Zuber, The Schizophrenia Working Group of the Psychiatric Genomics Consortium, The International Headache Genetics Consortium, Bendik S. Winsvold, John-Anker Zwart, David A. Collier, Rahul S. Desikan, Ingrid Melle, Thomas Werge, Anders M. Dale, Srdjan Djurovic, and Ole A. Andreassen in Biological Psychiatry. Published online August 2016 doi:10.1016/j.biopsych.2015.10.009

Feel free to share this Neuroscience News.
Join our Newsletter
I agree to have my personal information transferred to AWeber for Neuroscience Newsletter ( more information )
Sign up to receive our recent neuroscience headlines and summaries sent to your email once a day, totally free.
We hate spam and only use your email to contact you about newsletters. You can cancel your subscription any time.