Darwin's dual disease

There are two strongly contrasting public views of the role of psychological factors in relation to physical symptoms and illness: a strong belief that stress has physical consequences and, opposing it, a reluctance to accept that complaints such as fatigue and many others may have a partially or substantially psychological basis. These views reflect the traditional separation of mind and body which underlies our assumptions and frequently prevents any informed discussion.

This book argues powerfully against dualism but is very largely concerned with the ways in which psychological influences may have effects on the body, particularly via immune processes. This might not sound a compelling topic for the general reader but Paul Martin is an exceptional writer, a biologist who not only writes clearly and interestingly about his own subjects, but also is widely read in literature and history and uses illustrations from many sources. He chooses good scientific and literary examples to fit the argument. This is a very well-written book.

The main theme is the way threatening events and experiences and the whole range of emotional reactions can have profound effects on physical processes. The variety and weight of the examples are convincing. Martin has no time for traditional psychosomatic medicine which alleged specific relationships between certain psychological or personality conflicts and the onset of a range of major physical disorders.

Instead he marshals a large body of evidence about the psychological and behavioural impact of stressful events and of the often substantial physiological, neurological and immunological consequences. The chapters consider these main themes and they are skilfully combined in considering the examples of heart disease and cancer. The remarkable historical and literary allusions help the reader to understand the nature of the stresses being discussed, as well as their behavioural and clinical consequences.

There can be little doubt about the intimate inter-relationship of mind and body, but the author tells us not only about changes in physiology but also the implications for the onset and progression of disease. Here the evidence becomes thinner and somehow a key step appears to have been left out. As a result, the chapter on treatment is the weakest in the book.

It is unclear to what extent biological consequences of stress are clinically important. Martin is least good at persuading us that physiological changes do have pathological consequences that are of significance. There is, in fact, little evidence that psychosocial factors do have large direct consequences for physical morbidity and for mortality (with a few exceptions such as heart disease or perhaps the progression of cancer). Even in these instances, the contribution of psychological factors appears to be relatively small. We are faced with a contradiction between physiological and behavioural consequences of psychological and social stresses and remarkably little evidence that they are of direct aetiological significance. It is undoubtedly true that factors in lifestyle, such as diet, exercise, alcohol, drugs and a number of other elements are important risk factors, but Martin is arguing more than this. He is talking about a direct effect of mind on body which predisposes to or precipitates the onset or course of pathological processes. It is perhaps a fault of omission that the author's enthusiasm for his particular interests may leave readers with an impression that he is asserting and demonstrating a larger role for the mind as a cause of disease than is in fact the case.

Martin pays relatively little attention to the other important issue: the extent to which psychological variables may cause physical symptoms and syndromes such as chronic fatigue, pain and other unexplained disorders.

However, he takes the point both in sections on chronic fatigue and in a final chapter in which he examines the long-standing medical argument about Charles Darwin's many years of debilitating ill-health. Never understood in his own lifetime, the disease has been a diagnostic challenge to doctors ever since. Chagas's disease, widespread in South America, has been much favoured but, despite its ingenuity, this diagnosis seems less persuasive than psychological explanations for multiple recurrent but medically unexplained symptoms. The psychiatric and physical explanations have been debated as mutually exclusive alternatives. Martin rightly points out that this is just another futile continuation of mind/body dualism and argues that it would be better to look at an approach which admits the significance of both mind and body. This would help explain many of the nonspecific and medically unexplained symptoms patients complain about to general practitioners and patient-defined syndromes such as the variance of chronic fatigue, repetitive strain injury and Gulf war syndrome. It is indeed sad that a mind/body dualism prevents any reasoned discussion of the way in which psychological variables may contribute to these syndromes even though, in other areas of medicine, there is an eagerness to identify stress as a causal factor and psychological processes as being important in self-help and alternative treatment.

This book is a remarkable achievement. I have added it to my reference programme for use in academic work and recommended it to nonscientific friends as a book that, in the very best way, popularises science.

Richard Mayou is professor of psychiatry, University of Oxford.