I’m updating early because I’m moving apartments this weekend, but my general plan is to post every evening by nine-o-clock meds time (EST).
On the mental illness side: schizophrenia is not associated with genius or creativity. None of our evidence says it’s anything but severely impairing. Bipolar is associated with creativity despite fucking everyone over, but schizophrenia mostly just fucks people over, although there are people who do well at times. John Nash is a genius, but that’s not necesarily due to schizophrenia. People who are geniuses can also be crazy without a causal link. People who have bipolar are more likely to be creative, and not necessarily actually more creative. Inability to think clearly or concentrate, or being depressed or manic, can really do a number on your creativity.
On the evolutionary side: the detrimental effects of adaptations sometimes get undermentioned. An “successful” adaptation can severely impair most of the people who have it if, on average, there’s enough benefit for at least some people to “balance that out”. It doesn’t have to benefit an individual person. It doesn’t even have to benefit any of the people who actually have it! It might benefit copies of their genes that reside in their kin, instead. This is where schizophrenia may come into play – family members of people with schizophrenia display increased creativity (can provide cite later, seriously supposed to be packing my remaining crap right now).
Take-home point: If serious mental illnesses are adaptations (I’m not convinced they are, but I’m open to the possibility), they’re not beneficial for most affected people. If they were, we wouldn’t call them mental illnesses – a major requirement in the DSM is that a mental disorder cause marked impairment in functioning. It’s nice to think we’re all geniuses, but that stereotype covers up the crappy reality of just trying to make it day to day, let alone hold down a job or have good relationships.