Previously, I’ve talked about the relationship between certain flavors of nuttiness and high achievement in math and physics. There are other such associations. Poets, and some other kinds of creative artists, are more likely than average to be manic-depressive. Actually having schizophrenia does not seem to be especially common among people in creative professions, but some studies claim that they are more likely than average to have close relatives with schizophrenia.
Creativity has sometimes been associated with infectious diseases. Some thought that tuberculosis induced a kind of creative euphoria (spes phthisica), although I don’t put much stock in it. More plausibly, syphilis, which definitely does affect the brain, has been suspected of triggering a kind of genius. In Rats, Lice, and History, Hans Zinsser talked about the possible impact of effective chemotherapy on syphilis: “This might be a loss to civilisation: it has often been claimed that since so many brilliant men have had syphilis, much of the world’s greatest achievement was evidently formulated in brains stimulated by the cerebral irritation of an early general paresis. We omit reference to specific instances of this among our contemporaries only to avoid, for our publishers, the vulgar embarrassment of libel suits.”
There are other examples, but you get the gist. One of my pet peeves is people claiming that such things are adaptive, which is almost certainly untrue. They can occasionally be useful to society – sometimes, the idea that only a nut would have is valuable. In rare cases, useful to the individual (when you win the Nobel prize and suddenly acquire many new friends) – but any allele that turned you into a manic-depressive poet would decrease in frequency every generation, not least when carried by someone forced to spend his life as a hard-scrabble farmer, like most people over the past few thousand years. Mutational pressure, sand in the gears, is a far more likely explanation. As for the idea that personal creativity confers vast reproductive payoffs, on average, it is to laugh.
I compare this kind of intellectual product to ambergris, a highly-valued product of the “inglorious bowels of a sick whale.”