Prophets, Cults and Madness by Anthony Stevens, John Price. Duckworth, £18, pp 256. ISBN 0 7156 2940 9. Rating:

Schizophrenia is puzzling. The strong influence of genetics in its aetiology is not a sufficient and full explanation of why some people become hallucinated, deluded, disordered in thinking, and socially excluded. Its lifetime prevalence, just under 1% worldwide, is also unusual. The question of whether there might be some evolutionary advantage from the condition has therefore led to an increasingly influential evolutionary psychiatry. Stevens and Price are admirably qualified in this respect, and they have chosen cult leaders as the focus of their inquiry.

While some of the stories are repetitive, the tales of such people as John Forbes Nash (mathematical genius), Bhagwan Shree Rajnesh, Madam Blavatsky (founder of the Theosophical Society), and the more recent and dangerous David Koresh (of Waco fame) are colourful and informative. The authors suggest this motley crew have two things in common. Firstly, most of them suffered from a form of schizotypal personality disorder, maintaining bizarre beliefs but not sliding downhill into the negative symptoms of schizophrenia. Secondly, such cult leaders had a crucial evolutionary role. Their job was to help with the process of group splitting, so as to break up ancestral communities “when they had grown too big for their resources.”

The problem is that, despite a wide range of references and an easily readable style, the authors have a limited historical understanding. For example, they say that schizophrenia was first described in 1806, but numerous medieval doctorates, and of course Shakespeare's King Lear (the Tom o' Bedlam scenes), easily give the lie to this. Furthermore, they reiterate the notion that people with schizophrenia have low fertility (in contrast to the sexual hyperactivity of your average prophet), but the evidence for low fertility is scant indeed. Given that most people with chronic schizophrenia between the mid-19th and mid-20th centuries were locked up in asylums—socially sterilised, so to speak—it is not surprising that they didn't produce many children. In the era of community care women with schizophrenia seem to be having babies galore.

Another problem is the language. The authors talk of “heteropistic dispersal” and “mazeway resynthesis,” defining these terms nicely but tending to be dismissive about ordinary psychiatric theorising. For example, they consider the search by psychiatrists for known origins, definable courses, and definite cures in terms of mental illness as “largely an illusion” and insist that the meaning of existence is “an issue on which science remains speechless.” They say that therapists “should make use of the energy available for the function's realisation” (by which they mean the biological function of the schizotypal propensity) rather than “attacking it head on,” presumably with drugs, social and psychological therapies, and detailed research into brain function. It is that old medical battle between vitalism and mechanism, and prophets' predictions do badly in an evidence based world.