25 August 2009

Book Review: Wilson and Cory, The Evolutionary Epidemiology of Mania and Depression: A Theoretical and Empirical Interpretation of Mood Disorders

We should never judge books by their covers or indeed their typeset. Were we to do so, then this unglamorous-looking book by Daniel Wilson and Gerald Cory would be found wanting on both counts and in the process, we would end up ignoring an interesting set of questions, arguments, and hypotheses that claim to announce the new field of evolutionary epidemiology. Yet, just as the cover and typeset imply little concern for the aesthetic sensibilities of audiences, so too is it unclear who the authors intend for this manifesto. Although spotted with occasional references to arguments by Aristotle, Bacon, Nietzsche, Darwin, Tuke, and other figures of historical and scientific import, this cannot be a book intended for historians of science or medicine. It seems equally unlikely that most psychiatrists, ethologists, neuroscientists, or geneticists will have the time to dedicate to it – it is long but possesses a rather shorter message that the authors could have condensed into a review article. Nevertheless, this book may appeal to any scientist or clinician with a passion for big pictures, synoptic arguments, and theoretically ambitious syntheses. Its primary audience is probably one that does not yet exist – a new generation of scientists and clinicians who may become enamoured with its ideas and start applying Darwinian insights to medicine (if they ever get around to reading the book).

In this work, Daniel Wilson and Gerald Cory ask a very large question. They wish to know how and why it is that certain psychiatric disorders (presumed now to be at least partially genetic in origin) should appear with a population frequency far greater than evolutionary theories would permit for conditions so seemingly mal-adaptive (see pp. 130-1). In a subsequent argument that ranges across contemporary theories on the evolution of human sociality and its normal limits, through to discussions of psychopathology, population genetics, game theory, anthropology, sociology, and ultimately psychiatry, Wilson and Cory arrive at the startling conclusion that “neuropathologies of talent” probably possess evolutionary advantages that promote their survival in the population. While these neuropathologies appear, the authors claim, to be (and often are) mismatched to their industrial and post-industrial societies, the advantages conditions like mania or bipolar disorders bring in terms of innovation, creativity, intensity, imagination, ambition, and even sexual desire, offset the destructive tendencies that accompany these conditions, such as: self-medication with alcohol and drugs; paranoia; megalomania; and domestic instability. They thus pithily summarize the implications for psychiatry in their penultimate chapter: “It is important that any genetic therapies not assume disease is simply disease. Certain polymorphisms of at least utility are at risk of misguided therapy. Surely other gene systems now notable only as causes of individual disease will come to be seen, in the light of evolutionary epidemiological analysis, as fundamentally salubrious characteristics (p. 295).”

Wilson and Cory’s argument is elegant in its simplicity. If their theory is correct, moreover, then it is also easy to see that clinical and cultural perceptions of certain psychiatric diseases would necessarily have to change. The strength of their work is that it does do not sink into an unending search for neural structures that might circumscribe normal behaviour and thus explain pathological disorder. Instead, the authors search for genetic aetiologies: hence long and short discussions of Hamilton’s Rule, Hardy-Weinberg equilibriums, quasi-Mendelian genetics, and Hawk/Dove strategies appear with greater frequency than do discussions of the brain and nervous system. This strength, however, also reveals the central weaknesses of the text. Often the links between the many different areas of scientific knowledge are asserted rather than revealed, necessary constructs become black boxes (e.g. reptilian neo-cortex), hypothetical species (i.e. Hawks and Doves) supplement for hard examples, affective states (e.g. ego and empathy) become reified, and the relationship between reductive biological structures (e.g. neurotransmitters) and correlative behaviours (e.g. affection) assumed obvious and demonstrated. In consequence, like many clinical and scientific works that attempt a general statement, Wilson and Cory’s theoretical and empirical treatment, while rich and thoughtful, cannot fully deliver. Thus this work, which nevertheless represents a fine attempt at synthesis, may not get the attention it deserves.

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