Schizophrenia and the increased attractiveness of the non-conformist

Why is schizophrenia so common? It's a terrible disease, yet it's quite prevalent. Why hasn't evolution selected against it? How can schizophrenia have any adaptive advantages?

A single small and probably unreliable study claims a correlation between schizophrenic traits, being "non-conformist", (they say "creative", but they aren't talking about inventors and scientists) and have more sexual partners. The implication is that a mild dose of schizophrenia is good for one's mating opportunities, and that's enough of an advantage to keep the genes around in the population -- even when a full dose is horrible.

Science & Technology at Scientific American.com: Creativity Linked to Sexual Success and Schizophrenia

Psychologist Daniel Nettle of the University of Newcastle upon Tyne in England and his colleagues recruited 425 British men and women through advertisements in a small town newsletter and specialty lists for creative types. The researchers surveyed this group with questions designed to measure various schizophrenic behaviors, artistic output and sexual success, among other aspects of their personal history.

Results of that survey showed that people who displayed strong evidence of "unusual experiences" and "impulsive non-conformity"--two broad types of schizophrenic behavior--had more sexual partners than their peers did and were more likely to be involved in artistic pursuits, either professionally or as a hobby. Those who professionally pursued the arts had the highest average number of partners--5.5--compared to just over four for the less creative study participants.

... the finding, published yesterday in the Proceedings of the Royal Society (B), offers some insights into why schizophrenia, which seems to be passed from generation to generation and affects roughly 1 percent of people, does not disappear from the general population. In the study, even non-creative types who revealed an urge to resist conformity had more sexual success. In short, some of the traits associated with the debilitating mental illness can actually increase a person’s desirability...

There's something about this story that reminds me of how parasites spread themselves by altering their host's behavior. Could one think of a schizophrenia gene as a parasite that spread itself for altering host behaviors? Probably not, but it's a funny similarity.

The study is pretty slender stuff, but one can imagine several ways in which "non-conformity" might be adaptive -- even beyond more sex partners. It would be interesting if schizophrenia were the price we pay for keeping some non-conformists around...