September 05, 2007

Schizophrenia Genes due to Human Evolution, Research Suggests

As we've reported in the past, research suggests that genetic schizophrenia risk may be the result of selection during evolution for some traits -- possibly in the area of creativity or other cognitive abilities -- which provide benefits for many people, but which can be negative (i.e. increase risk of schizophrenia) in certain genetic combinations, or when a person with these genes are exposed to certain environmental factors.

A new study done at the University of Bath in England provides evidence that supports this theory that schizophrenia risk is, in part, a maladaptive by-product, or side effect, of adaptive changes during human evolution.

The study authors suggest that several genes with strong associations to schizophrenia have evolved rapidly due to selection during human evolution, according to new research in the British publication called the Proceedings of the Royal Society B.

Researchers found a higher prevalence of the influence of so-called positive selection on genes or gene regions known to be associated with the disorder than a comparable control set of non-associated genes, functioning in similar neuronal processes.

This is consistent with the theory that positive selection may play a role in the persistence of schizophrenia at a frequency of approximately one per cent in human populations around the world, despite its strong effects on ability to have children and its frequent inheritance from generation-to-generation.

It also provides genetic evidence consistent with the long-standing theory that schizophrenia represents, in part, a maladaptive by-product of adaptive changes during human evolution - possibly to do with aspects of creativity and human cognition.

“The world-wide presence of this disorder at an appreciable frequency, despite its impact on human health and reproductive fitness, is somewhat of a paradox,” said Dr Steve Dorus from the University of Bath, who worked with Dr Bernard Crespi from Simon Fraser University (Canada) and Dr Kyle Summers from East Carolina University (USA) on the research.

“This may be explained by the existing theory that the condition represents, in part, a by-product of adaptive changes during human evolution.

“Our finding that positive evolutionary processes have impacted genes underlying the disorder is consistent with this idea.

“However, the selective forces influencing the evolution of these genes remain unknown.

“Given the complex genetic nature of the condition, selection may be mediated by a diverse array of neurodevelopmental, neurophysiological and psychological mechanisms.

“Schizophrenia has also been associated with creativity throughout recorded history, but whether this link has a genetic basis is certainly not yet clear.”

The researchers analysed the molecular evolution of the 76 genes that have the strongest genetic association with the disorder.

They surveyed human polymorphisms - discrete changes in the human genome that vary between individuals - for very recent selective events within specific human populations.

They also compared genes between mammalian species to identify selection on primate lineages that are relevant to the evolution of humans and the disorder.

The research identified evidence for positive selection on a variety of genes, including three genes that have the best functional or reproducible associations with the disorder: disrupted in schizophrenia (DISC1), dystrobrevin-binding protein 1 (DTNBP1) and neuregulin 1 (NRG1).

“For the first time it is possible to complement our genetic understanding of the disorder with substantial evolutionary and comparative genomic analyses,” said Dr Dorus.

“Decades of intensive research, using association and inheritance studies between affected and non-affected siblings, has resulted in a much clearer understanding of the genetic basis of the disorder.

“Hopefully, a better understanding of the evolution of the substrates underlying the disease will assist in characterizing how they are dysregulated in the disorder.

“Understanding the impact of positive selection may also help refine hypotheses concerning genetic links between schizophrenia and aspects of human creativity and cognition.

The research was funded in part by the Natural Sciences and Engineering Research Council of Canada, East Carolina University and the National Institutes of Health.

More Reading: It's No Delusion: Evolution May Favor Schizophrenia Genes (Scientific American)

Source: Press release from the University of Bath

Source Journal Paper: Adaptive evolution of genes underlying schizophrenia


I suggested that we are the new Neanderthals, an off shoot in evolution in modern times due an unsuccessful adaptive response to our environment etc..It was a tongue in cheek post..And I don't think the concept went down to well lol.

Posted by: Grissom at September 5, 2007 09:05 AM

Nah we just have sensitivties to pollutants and general toxins. We are the social and climatic detectors. And the more of us there are
usually suggests whats happening in our local weather system.... Neanderthals no, Druids and earthly beings yes!!! I am Gandalf amongst the hobbits LOL Or Abraham, Or even Jesus! I am JFK, and Richard Nixon!!! LOL
Oh I suggests reading some Focault he seems to see sense in madness!

Posted by: Max at September 5, 2007 10:56 AM

I know that scientists have found an intelligence gene and that most of us have a mixture of the old and new genes a small percentage have the old gene but but some have the new gene associated with intelligence . I’m just wondering how different our genes have to be to qualify as a sub type or a species within a species , there must be a bench mark to quantify it, it would be handy, the next time someone asked me what’s wrong with me I could say “Oh I’m a sub type B3”

Posted by: Grissom at September 5, 2007 12:06 PM

I really wonder if there is such a thing as adaptive benefit for carriers of genes linked to schizophrenia. If you go for the statistics, they will demonstrate that the mayority of families linked with schizophrenia are just plain normal intelligence people and only a small amount, consistant with IQ rates in the normal population are maybe highly intelligent or extremely creative.

Posted by: Joyride at September 5, 2007 02:07 PM

I recall reading something recently from a rather dazed and confused researcher who was bewildered that we still have people walking the face of the earth with sz. Apparently, evolution dictates that the disease should have been wiped out because of the adverse impact on potential for mating for those afflicted.

Well, sometimes we are just victims of our belief systems that we buy wholesale into without question. Of course, if you base your conclusions on the evidence you see instead of letting your wholesale belief system (be that science or religion)drive your speculations then maybe you won't be dazed and confused. Is there any evidence that the strangest (no offense: strange does not = sz)to the most undesirable people manage to reproduce. Also, given that most healthy people in families stricken with this disease do not seem to consider electing not to reproduce, this theory is just more evolutionary postulating. Also, late onset for sick people in some families would deprive some of making that choice.

Contradictory to this silly theory, the only thing that might diminish the incident of this disease at least for a time (until the same degenerative influences rather than natural selection for some desirable traits re-emerge in future generations) is for people, like me, to elect not to fulfill their hard-wired instincts to reproduce knockoffs of themselves and play the genetic lottery at someone else's expense.

Posted by: jen at September 5, 2007 05:55 PM

Um I think everyone has the right to reproduce, diverse genetics lead to a healthy system. And when this is impeded on the system usually fails. I think you should fufilll your instincts they are there for a reason, why castrate yourself, genetics is only a small factor. People will get it at the same rate even if we where all castrated! And yes that researcher was a bit bewildered and probably tired. Cause he probably has been taught to be monological and not polylogical. Besides if it doesn't prevent it, then why do it? If i am good looking enough and a good provider then their is no reason why i shouldn't reproduce. Besides Nietzsche is dead and shall remain dead!

Posted by: Max at September 6, 2007 05:31 AM

the so called scientific american article you cite also starts off by saying multiple personalities is a mark of sz, which everyone here knows is not true

Posted by: richard at September 13, 2007 07:07 PM

Richard - you're absolutely right - I've sent a letter to the editor of the publication to correct them. Thanks for letting us know.

Posted by: szadmin at September 13, 2007 09:19 PM

Schizophrenia is something that occures primarily is America. Think! wouldn't you go crazy without a collective unconciousness? The truth is that you cant answer that question if your an American because you have bought into it as a genetic etiology. If you really want to believe that it exists without being induced through neuroleptic medication backed by theories out of Palo Alto then go on, I'll pray for you.

Posted by: sirercwil2005 at September 17, 2007 09:25 PM

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