Part of my major hypothesis is that the industrial/digital age and processed, low-nutrient food has brought out more severe and different phenotypes of underlying vulnerabilities, and has also brought out seemingly new illnesses ("atypical depression"). Thus a less destructive phenotype (a mildly paranoid schizotypal person, for example, who will be more creative than the average person, as compared to full-blown schizophrenia, which impairs functioning to a terrible extent) will persist in the population due to selective advantage for certain traits.
My only previous article on "real" evolutionary psychiatry can be found here: The Creative Advantage.
Well. It is fitting the first of the two papers today comes from Medical Hypothesis. Melissa McEwen sent it to me - I think she likes that journal because it is crazy and it makes her laugh. (Here is advice for those aspiring to be published there:
I have no publications, myself, though I have assisted in some research efforts. My mentor would like me to cobble something together from all the research I've done for the blog on affective disorders, or something. I never did fancy myself much of an academic… thus never felt the motivation to write anything boring enough to be published in a journal ;-)… however, it would certainly add to my street cred. I don't know that I can write the exotic papers for Medical Hypothesis, however (Melissa sent me a paper previously about some sort of reptile origin theory of illness? I can't remember, but it was hysterical, and it must have slipped through part of the editorial process as it was also mostly incoherent). Back to evolutionary psychiatry!
Evolutionary origin of bipolar disorder - revised (EOBD-R) is the paper in question, by one Julia A. Sherman of Madison, Wisconsin. A quick google search brings up her original EOBD (sans R) from 2002. And as much as I make light of Medical Hypothesis, I do have to admire the originality of the paper, noting that it is wildly speculative and the basic premise is most likely incorrect.
Ms. Sherman connects the dots between the circadian rhythm issues and vulnerability to bipolar disorder (manic episodes are known to peak in the spring time, when the light increases exponentially day by day in extremely northern or southern latitudes.) In a nutshell, the EOBD suggests that bipolar disorder developed as an adaptive trait in the northern temperate zones which had more extreme winters during the ice age. If you were hypomanic all spring and summer, you got a lot of stuff done, and then you could slow down and "hibernate" (be depressed) during the winter and not use much energy. The "R" or revision in question actually brings in the interesting bit of Neanderthal DNA that all of us non-San Bushmen (or otherwise directly derived from Africa without side-stepping through Europe or Asia and coming up close and very personal with other hominids) seem to have. Ms. Sherman thinks that bipolar disorder is a Neanderthal trait.
Hmmm. She brings in the observations of a German psychiatrist from the early 20th century, E. Kretchmer, who noted that folks with bipolar disorder tended to be of a certain "pyknic" constitutional type. They have a "thick trunk, relatively short limbs, and a big head on a short, thick neck." Apparently, several other researchers in the early 20th century, when they were really into measuring heads and body sizes and making silly claims based on the measurements found that manic-depressive patients were more likely to be pyknic (endomorphs), and schizophrenics were more likely to be "leptosomic" (ectomorphs). A much newer study in 2003 also confirmed this finding. Sherman believes it is striking that Neanderthals are also described as having big bellies and short limbs. Interesting. In addition, people of African descent apparently have lower incidence of bipolar disorder in some studies Sherman cites. However, there is no reliable data among truly purely African populations such as the San.
There is more to the paper, but I hit the highlights. I'm not entirely sure what to think. There is no question that bipolar disorder has a seasonal component and that light and dark therapies can be useful. Hypomania, with the extended bursts of drive, energy, and creativity can also be very adaptive. And one can imagine being moderately depressed during a cold, dark winter might keep a small tribe of Neanderthal out of each other's hair, when there might have been nothing much to do anyway. I think the pyknik bit is a little ridiculous - as we know, actually, both schizophrenia and bipolar disorder are related to metabolic syndrome, even in people who have never been on medicines. I also would bet a poodle that there are San bushmen with some bipolar disorder out there, but symptoms might be attenuated by their latitude and hunter-gatherer lifestyle with plenty of socialization and exercise (though they do like those omega 6-filled mongongo nuts), according to my own wildly speculative theorizing…
The second paper is far less... imaginative and was published in the much more staid Journal of Affective Disorders. Creativity and affective temperaments in non-clinical professional artists: An empirical psychometric investigation. These researchers looked at 152 undergraduates in art school (or other creative majors) vs. 152 undergraduates who were in majors predicted to lead to professions "mostly requiring the application of learned rules" (like accounting, I suspect). The students were tested with several standard measures to detect subclinical and clinical manifestation of cyclothymia (a mild variation of bipolar disorder), and also other scales of general health and demographic data. I don't think it will surprise anyone to know that the creative students were significantly more likely to score into the cyclothymic range on these scales.
An interesting quote from the paper:
Positive mood, and happiness in particular, was postulated to fuel creativity. Enhanced positive affect is a feature of both hypomania and mania, which are core symptoms of bipolar disorder and may predispose people within the manic-depression/bipolar disorder spectrum to creativity. By contrast, postulated that depression might provide fresh insights which can be executed into the artistic oeuvre during the energized phases of cyclothymia.
So it appears that bipolar disorder is linked to creativity, which may have an adaptive advantage. I don't think that is particularly controversial, but it is nice to see more studies on the subject. Now were Neanderthals more creative than homo sapiens? At least in the springtime? That might help Julia Sherman's hypothesis!
Edited to add - a Neanderthal winter love song? By Primitive Radio Gods (right click to open in new tab).