From an article on how nutty “creative types” get laid more often than their normal peers:
The study also included some known schizophrenics. And Nettle’s personality surveys revealed that the artists and poets shared certain traits with schizophrenics. Again, perhaps no big surprise. But these traits are linked with increased sexual activity, Nettle and his colleagues say (though full-blown schizophrenic patients tend to withdraw from society and have less active sex lives).
Insofar as evolution is concerned, maybe teetering on the brink is a good thing, the researchers speculate.
“These personality traits can manifest themselves in negative ways, in that a person with them is likely to be prone to the shadows of full-blown mental illness such as depression and suicidal thoughts,” Nettle said. “This research shows there are positive reasons, such as their role in mate attraction and species survival, for why these characteristics are still around.”
Also:
For example, the first of our ancestors to empathize and read facial expressions had a striking advantage. They could confirm their own social status and convince others to share food and shelter. But too much emotional acuity — when individuals overanalyze every grimace — can cause a motivational nervousness about one’s social value to morph into a relentless handicapping anxiety.
Pondering the future
Another cognitive innovation made it possible to compare potential futures. While other animals focus on the present, only humans, said Geary, “sit and worry about what will happen three years from now if I do that or this.” Our ability to think things over, and over, can be counterproductive and lead to obsessive tendencies.
Certain types of depression, however, Geary continued, may be advantageous. The lethargy and disrupted mental state can help us disengage from unattainable goals — whether it is an unrequited love or an exalted social position. Evolution likely favored individuals who pause and reassess ambitions, instead of wasting energy being blindly optimistic.
Natural selection also likely held the door open for disorders such as attention deficit. Quickly abandoning a low stimulus situation was more helpful for male hunters than female gatherers, writes Nesse, which may explain why boys are five times more likely than girls to be hyperactive.
Similarly, in its mildest form, bipolar disorder can increase productivity and creativity. Bipolar individuals (and their relatives) also often have more sex than average people, Geary noted.
Sex, and survival of one’s kids, is the whole point — as far as nature is concerned. Sometimes unpleasant mental states lead to greater reproductive success, said Geary, “so these genes stay in the gene pool.”