MENTAL DISORDERS

The purpose of the Oxford Monographs is to 'provide handbooks relevant to particular specialisms'. This volume is intended primarily for the clinical psychiatrist, who is likely to find its scope wider than he needs. He will, however, be rewarded with a panoramic view of the models and methods of clinical genetics, and come across many examples of how the genetical approach affects the way of looking at clinical problems. Six chapters are devoted to the rare neurometabolic and autosomal anomalies causing severe mental and physical defect in children, and these will be invaluable for reference. So far, however, 'inborn errors' have not been demonstrated in the common forms of mental illness. Among the relatives of the rare genes causing subnormality in the homozygous state psychiatric disturbances are not more frequent than might occur by chance, and the psychotic states which may be seen in the early stages of Wilson's disease and Huntington's chorea, and in epilepsy, are symptomatic and not genetically related to schizophrenia as it occurs in other families. Sex chromosome anomalies, however, now enter into reckoning in the psychopathic disorders, and to a less extent the psychoses, and this may lead to a better understanding of these conditions. In contrast to the situation in severe subnormality, distinguishing physical characters are absent in the adult psychoses, and persisting metabolic anomalies have not yet been identified. The evidence from pedigree and twin studies is open to non-genetical interpretations, specially in schizophrenia. Here the authors take a hard line with purely psychogenic theories, on the grounds that they are vague and incapable of verification. They can cite the evidence from monozygotic pairs separated early in life, and from the adoption studies, in support of biologically rather than psychosocially transmitted factors. Concordance for schizophrenia in monozygotic twins is, however, not higher than 40%. Phenocopies of organic and perhaps even of psychogenic origin do occur, though only as a small proportion of the whole. Genetical models are discussed at length. Genetical heterogeneity is regarded as only quite probable. The hypothesis of a major gene, with a frequency of 0-03, full manifestation in all homozygotes and about one quarter of heterozygotes would fit most of the data well. As the authors say, it would be very desirable to be able to recognize the genotype apart from the psychosis, but in practice clinical acumen is baffled by the difficulty of defining the traits considered to be part of the 'schizophrenic spectrum'. The remaining chapters deal with affective disorders, deviations of personality and neurotic reactions, senescence, senile and presenile dementia, epilepsy, and mental subnormality associated with normal variation in intelligence. Genetical studies do not give support to unitary hypotheses. Among the affective disorders, for instance, bipolar disorders, with swings into both mania and depression at different times, appear to be genetically distinct from unipolar disorders, where the swings are depressive only. 'Involutional melancholia' probably corresponds mainly with the latter. Even in the neuroses, in which the type and severity of environmental stress is important, some degrees of genetical specificity exists, at least in the predisposition to anxiety and obsessional states. There are some interesting reflections about sex differences in alcoholism and delinquency, and about parental age and the sex-ratio of children and sibs in homosexuality. As for epilepsy, its genetical connections with psychiatric disorders seem to be surprisingly small. Eventually, the genetics of mental illness may prove to be extremely complex, but in the meantime the authors' attitude, that the most economical hypotheses are heuristically the most valuable, seems sound. With modem techniques, numerous lines of research are open, and the would-be psychiatric geneticist should find many ideas in this highly informative book. The style is as lucid and the discussion as critical as is to be expected of the authors, and the production is excellent. DAVID W. K. KAY