Schizophrenia Emerged After Humans Diverged From Neanderthals

Reports new study in Biological Psychiatry

Philadelphia, PA, August 15, 2016

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.

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.”

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Notes for editors
The article is "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 (doi: 10.1016/j.biopsych.2015.10.009). It appears in Biological Psychiatry, volume 80, issue 4 (2016), published by Elsevier.

Copies of this paper are available to credentialed journalists upon request; please contact Rhiannon Bugno at +1 214 648 0880 or biol.psych@utsouthwestern.edu. Journalists wishing to interview the authors may contact Ole A. Andreassen at o.a.andreassen@medisin.uio.no.

The authors’ affiliations, and disclosures of financial and conflicts of interests are available in the article.

John H. Krystal, M.D., is Chairman of the Department of Psychiatry at the Yale University School of Medicine, Chief of Psychiatry at Yale-New Haven Hospital, and a research psychiatrist at the VA Connecticut Healthcare System. His disclosures of financial and conflicts of interests are available here.

About Biological Psychiatry
Biological Psychiatry is the official journal of the Society of Biological Psychiatry, whose purpose is to promote excellence in scientific research and education in fields that investigate the nature, causes, mechanisms and treatments of disorders of thought, emotion, or behavior. In accord with this mission, this peer-reviewed, rapid-publication, international journal publishes both basic and clinical contributions from all disciplines and research areas relevant to the pathophysiology and treatment of major psychiatric disorders.

The journal publishes novel results of original research which represent an important new lead or significant impact on the field, particularly those addressing genetic and environmental risk factors, neural circuitry and neurochemistry, and important new therapeutic approaches. Reviews and commentaries that focus on topics of current research and interest are also encouraged.

Biological Psychiatry is one of the most selective and highly cited journals in the field of psychiatric neuroscience. It is ranked 5th out of 140 Psychiatry titles and 11th out of 256 Neurosciences titles in the Journal Citations Reports® published by Thomson Reuters. The 2015 Impact Factor score for Biological Psychiatry is 11.212.

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Media contact
Rhiannon Bugno
Editorial Office, Biological Psychiatry
+1 214 648 0880
biol.psych@utsouthwestern.edu