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Psychopathology and the social brain

Bernard Crespi

Why do some people suffer from autism, or schizophrenia, or bipolar disorder? At root, these psychopathologies and others might all result from malfunctions in the “social brain,” says Bernard Crespi, an evolutionary biologist at Simon Fraser University, who spoke as part of the UTSC New Frontiers Seminar Series last week.

Crespi thinks autism, depression, schizophrenia and other seemingly unrelated diseases actually have something in common – they result when social cognition is either too greatly enhanced or too greatly diminished.

 “What I describe is a new conceptual model for an evolutionary basis for major human mental illness,” Crespi says. “We have normality in the middle. If you dial down these (social) traits you have something that looks like autism. If you dial up these traits you have something that looks like some combination of traits from schizophrenia, bipolar disease and major depression.”

Evolution has fitted people with specialized social intelligence, he says. Language is one obvious example. Less obvious are things like: automatically meeting the eyes and following the gazes of other people, understanding what other people are thinking and feeling empathy with them, and having a distinct sense of self.

Crespi thinks that you can rank psychopathologies on a continuum according to whether social cognition is turned too far up or too far down. On one end are the autism spectrum disorders, in which speech is often delayed, social cues aren't easily understood, empathy with other people is lacking, and thinking tends to be mechanistic.

On the other end are disorders such as schizophrenia, depression, and bipolar disorder. In these, social cognition can be thought of as too active. For instance, paranoid people are not only aware that other people have their own thoughts, but they have an exaggerated view of how much and what other people are thinking about them. Schizophrenics may have a heightened sense of self in the form of delusions of grandeur. Depressed people often feel heightened social emotions such as shame or guilt.

"In the world of psychology this is something which is absolutely radical, the idea that disorders like this could be opposite to one another,” Crespi says.

He thinks that the cause has to do with something called gene imprinting. This is when only one set of genes for a trait, from either the mother or father, is expressed. Gene imprinting occurs normally and usually causes no problems. But when some paternal traits are over-expressed it could lead to disorders tending toward the autistic side of the spectrum, while over-expression of maternal traits could lead to disorders on the psychotic/schizophrenic/depressive side, Crespi says.

This work has strong medical implications,” says Crespi, “and it also feeds back on understanding the evolution of humans and the various disorders, and can actually give you insight into how humans evolved.”



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