Guardian Unlimited | Arts news | Mental illness link to art and sex
A survey comparing mental health and the number of sexual partners among the general population, artists and schizophrenics found that artists are more likely to share key behavioural traits with schizophrenics, and that they have on average twice as many sexual partners as the rest of the population.

And

According to Dr Nettle, the results suggest that the creativity of some artists is fuelled by the unique world view mental illness can provide, but without the completely debilitating aspects of the condition. Instead, the artists are able to direct their creativity into artistic projects.

And

Dr Nettle believes that this provides the answer to the question posed. Some of the genes that predispose to schizophrenia might be carried by artists and in many cases play a factor in their creativity, but because the artists do not develop full-blown schizophrenia and are able to direct their creativity, they are able to pass the genes on to their children.

Or – a little bit of anything can be good, but too much is not… There is a reverse side to everything – no light without darkness. For every Picasso there might be a handful of people who are full-blown schizophrenics. I think this should show us the importance of any cultured society taking good care of people with mental illnesses – since there is only a shade between genius and autism, and between visionary artist and schizophrenia.