When I sit down to ponder about Schizophrenia one of the first questions that comes to mind is:
What are the evolutionary benefits to such a disorder?
Seeing as there is a universal prevalence rate of approxiamately 1.1% of the population, schizophrenia could not be due to chance mutations. Evolutionary psychologists claim that this standard prevalence rate implies that schizophrenia existed when Homo sapiens emigrated out of Africa. So with this long history of the disorder, nature had plenty of time to extinguish this maladaptive disorder. Yet, the mental illness continues to plague the globe at an unwavering rate; even instances in remote populations, such as Australian Aboriginals and Nepali villagers, remain constant. Hence, schizophrenia must have evolved over time for some mysterious purpose or as a negative byproduct of an evolutionary benefit.
One of my first conclusions points to the fuzzy line between mental illness and ingenuity. Perhaps schizophrenics are on the opposite spectrum of geniuses. Depending on the genetic factors and environmental influences, modified brain chemistry may lead individuals to either gain creative insight into particular fields or result in hallucinations, delusions, affective blunting, or various other schizophrenic symptoms.
I looked further into potential theories of the evolutionary basis of schizophrenia and discovered the following theories:
Schizophrenia as an evolutionary advantage to the group:
- Religious based delusions that enhanced religious rituals ( perhaps justifying the hallucinations of religious prophets)
- group-splitting hypothesis of schizophrenia: schizophrenic individuals were usually prominent enough (tended to show signs of leadership) in tribes that their symptoms would result in breaking up the group into smaller units.
- Protective function: the symptoms of schizophrenia forces the individual to be in a state of constant alertness, which enhanced territorial instincts.
Schizophrenia as an evolutionary by-product:
- Crow’s theory: psychosis is a result of cerebral asymmetry, which evolved in conjunction with human’s language ability; the core deficit in psychosis is a failure of segregation of right from left hemisphere functions.
- An extreme variant of normal social skills or a trade-off for complex social cognition
- Horribin’s theory: negative alterations in the neuronal membrane phospholipid metabolism, or fatty acids, that lead to enhanced creativity may result in schizophrenia. He implies that schizophrenia is a whole body disorder, not just a brain problem. (To read more about this interesting theory refer to The madness of Adam and Eve: How schizophrenia shaped humanity by Horribin (2001)).
Schizophrenia as an evolutionary advantage on the individual level:
- Reproductive advantage: schizophrenics have a higher resistance to many things: to shock, visceral perforation, high doses of histamine, insulin, thyroxin, and other physiologically active substances, as well as infection and many allergies.
- Physiological advantage: As Horribin’s claims, schizophrenia is a whole body disorder demonstrated through the unusual posture, gait, and body shape of diagnosed individuals. The high fever of schizophrenic individuals provides further evidence to Horribin’s theory.
- Psychological advantage: there is no evidence that links psychosis, particularly schizophrenia, with creativity (which disproves my hypothesis!)
Schizophrenia as an evolutionary advantage at the kin level:
- Schizotypal personality: schizophrenia falls on a genetic continuum where relatives show schizotypal traits and features, even when they are not diagnosed as schizophrenic.
- Milder forms of schizophrenia tend to exhibit more divergent thinking
So, perhaps the increased severity in developed countries is a biological reaction to the norms and cultural standard society reinforces. Perhaps Western culture encourages the schizotypal personalities, which lead to the genetic mutations and thus cognitive and emotional impairments that are characteristic of schizophrenia.
Source: Nichols, Catherine (2009). “Is there an Evolutionary Advantage of Schizophrenia?” Personality, Psychopathology, and Original Minds. 46,8 : Pages 832-838.
On Psychology and Neuroscience 
Really interesting post, Lia! What a fascinating question. I loved reading further on this topic. After reading this and watching the 20/20 video that Sharonda posted, it may not seem that schizophrenia is related to creativity, or maybe the creativity that we define in our societal terms. I think the girls in the video have a different type of creativity in that I was shocked that at ten years old, they were telling fabricated stories about things that animals or people were telling them and also sharing stories about killing people and how they would do it. We would probably call this destructiveness.
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I really enjoyed reading through these different theories on why schizophrenia keeps popping up in the gene pool. It would seem that there is at least some evolutionary advantage if it has seemingly prevaled for so long. On a very primitive level it is interesting to think of schizophrenia as constant awareness. In the developed world it does make sense that we value original thinking and thus some characteristics of schizophrenia. Also I think that although there is no evidence linking creativity to schizophrenia, a relationship could be found with a careful definition of creativity.
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It’s a good point to bring up why such a small percentage of people are still suffering from this disorder, why hasn’t it disappeared yet? It’s hard to think that a disorder as debilitating as Schizophrenia can be advantageous. These are very different views of Schizophrenia but I still say it does more harm than good.
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Lia, this is such an interesting post. It’s funny and somewhat alarming how we always look at schizophrenia in terms of the symptoms and possible causes from observing brain structures or behaviors, never in terms of an evolutionary perspective. Viewing this topic from an evolutionary sense can stimulate further research as to the cause of schizophrenia, and maybe can even help determine possible treatment, by allowing researchers to focus less on gross anatomy and behavioral observations and more on the biological and societal implications. The question you have posed is very compelling and the evidence you have demonstrated is equally as insightful. It will be interesting to see more research that comes from this.
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This reminds me of a game I used to play with my sister; I would take something that is clearly negative, and try and make her believe it was, in fact positive–for example, being hit in the stomach will make you tougher, stronger, (and thus indirectly sexier). I can sort of see how some of these things could be advantageous, but on the whole I would still obviously rather not have schizophrenia. It’s still interesting to try and get to the root of why it’s showing up–honestly, it’s difficult to imagine how some of these abnormalities have continued for so very long. There’s really no good reason why, if it’s a significantly genetic disorder it should still be around: Unless we’ve reached a base point where evolution can no longer reduce its incidence and environmental factors keep reviving it in family lines–perhaps not for the current generation, but for a later one.
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I had never thought of schizophrenia having an evolutionary benefit before! It’s such a neat perspective to take on the subject. I really enjoyed reading through the hypotheses. Schizophrenia has such a bad connotation, so it is interesting to think that at some point they could have led tribal splits and been responsible for the formation of new groups. It will be interesting to see if any of these thoughts are expanded upon or confirmed.
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To view schizophrenia through a positive lens is an extremely hard thing to do because the idea of it is so negative. People only view it in terms of the harm it has done to people’s lives. I never would have believed that schizophrenia can positively influence populations and the individual who has the disease. One great point that you made was stating that because the disease has been around for so long, it must have had an evolutionary purpose at some time. This is true for certain diseases like sickle cell, but there are still many other developmental diseases that I find hard to believe had a purpose in promoting evolution. I was extremely surprised by the group-splitting hypothesis because one of the negative symptoms of schizophrenia is social withdrawal. Maybe the symptoms of the disease have been altered over the years.
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This is really thought provoking. There are some problems with some of the theories put forward, though, while others could have some really compelling support. First of all, the idea that schizophrenia MUST have some sort of evolutionary benefit is somewhat simplistic. That’s not necessarily the case – it could just be something that isn’t lethal in cases where the disease is fully present, and as was thoughtfully laid out in your research, can be beneficial in milder cases, with more divergent (and presumably creative?) thinking. Maybe it’s not the disease itself that’s beneficial, but rather that it’s not cripplingly harmful until after child-rearing age, and can benefit people who have it mildly. Kayleigh brought up the idea of Sickle Cell Anemia, which has a similar function – harmful with full presence, beneficial with partial. Back to the point of necessity of evolutionary functioning, it could be just barely good enough to slow the weeding out of the disorder over time. I also think it’s important to stress Horribin’s conversive theory – if schizophrenia is a common side effect linked to creativity, maybe it’s hard enough to eliminate schizophrenia as a mutation and beneficial enough to have the extra creativity that it had more reason to propagate than fade. Maybe the 10% of really creative individuals in the population do more good than the 1% of schizophrenics do harm.
I think that your point about the increased prevalence of schizophrenia in Western cultures is right on. In Adolescent and Adult Development, we discussed the characteristic of white affluent culture to repress and suppress individuality in preference of conformity, especially in high schools (quite relevant to developmental period for schizophrenia).
My cynical side finds the idea of religion being benefited by schizophrenia-inspired visions to be quite interesting, and the thought of paranoia increasing reaction ability to survival pertinent effects does seem quite logical. Delusions and hallucinations might not be that bad if they keep you scared enough to stay alive for a few more years of mating time (after which it doesn’t matter much). Maybe that’s part of it, too – the idea that schizophrenia hits at a time frame that even with the onset of the disorder, you’d still have some time to mate before the increased stress level had major mental repercussions. In that time, perhaps, it might be beneficial by increasing paranoia and resistance to homeostatic disruption.
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The perspective of schizophrenia as evolutionary advantageous definitely calls into question the advantages of any other heritable mental disorders. This may be a tangent, but this reminds of an article I read a while ago in the nytimes about the possible advantages of depression. Take a look: http://www.nytimes.com/2010/02/28/magazine/28depression-t.html?pagewanted=1
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An evolutionary perspective on schizophrenia is one that I have never considered before. You bring up a good question about why this disorder, and others like it, continue to exist. It could be due to a combination of the theories you mentioned. Reading this made me consider another couple of explanations: Perhaps because schizophrenia typically becomes noticeable in early adulthood and people used to get married a lot earlier than they do now, the disorder did not interfere with marriage and reproduction, and so did not allow the process of natural selection to come into play as much. Also, in today’s high-stress world, it is possible that schizophrenia is more easily triggered. These theories have obvious holes in them, but I think it’s possible that they were contributing factors along with many Lia mentioned.
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Lia this is great. I wonder, given all you have presented, if this same argument could be made for other psychological pathologies. What other pathologies share similar characteristics? What would this tell us about human kind?
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I am trying to find some use for schizophrenia.
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I recently posted the following comments on the “evolutionary psychology site for linked-in. l thought you might find it fo interest: Thank you for your interesting comments on belief, neuroscience, art, etc. You all seem like very intelligent, articulate, and accomplished individuals. I am a little disappointed however. I joined the evolutionary psychology group for a very specific reason. I am seeking thoughts concerning a burning question I have had for many years. It concerns schizophrenia. Specifically the question is: If persons with schizophrenia do not reproduce at the rate of those in the rest of the population, why has schizophrenia (and similar psychotic conditions) not died out many generations ago? Authors publishing in the journal, Schizophrenia Research, are currently suggesting that schizophrenia is 80% heretable. If this is the case, is it possible that there might be some DNA material in the non-affected family members of persons with schizophrenia, etc, that enable those family members to perform in such a manner that compensates for the many cognitive, perceptual, and emotional “deficits’ evident in the phenotypes of the family members having these psychotic conditions? As we know, the likes of James Joyce, Albert Einstein, James Watson, Bertrand Russell, Clark Clifford, and many other highly accomplished individuals all parented children that were diagnosed with schizophrenia. Might there be some connection here? Is there anyone in this esteemed group of persons with a stated interest in evolutionary psychology who might have any thoughts or guidance on this question? Thank you for any consideration that any of you may give to this request?
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There is no evidence of schizophrenia existing before the 1770’s. James Tilly Matthews is the first documented case in 1809.
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There is no evidence of what we now call schizophrenia existing before the 1770’s. The first documented case is James Tilly Matthews in 1809.
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I think it’s society as a fragmented whole that is reflected, or induces a fragmented personality. We all react in a different manner to different conditions imposed on us, by society. But the overall characteristic that defines us, or the color, is still present, that on its turn reflects society as a whole, or at least culture. Divergent thinking charasteristics of a schizophrenic are then necessary, as the extremes of this fragmented personality are not totally clear to ordinary (or less schizophrenic) members of a society, for innovation; a daring motive. But nevertheless, the core of extreme behaviour, or these fragments, will not be accepted, as they are not clear, despite their identity reflecting the necessity of the whole. People usually fear extremes, that, maybe, are a part of their own evolved selves, some time in the future of humanity. All of this may imply the link between creativity and schizophrenia, or between the god delusion and sacrifice, the saviour complex and the creator, or the innovator and highly intelligent scientist.
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