If one can agree to these authors' broad definition of affective disorder, one cannot fail to be impressed with their finding that affective disorders occur three times as frequently as schizophrenia in the general population. The authors comprehensively review the diverse findings of epidemiological surveys and studies subclassifying the affective disorders. They question the biological validity of depressive symptom-clusters obtained by factor analytic techniques and conclude that, as yet, the clinical picture and predisposing psychological factors have not resulted in any clear-cut separation of depressive subtypes from the larger group of patients with affective symptoms.
An important point of the book— that use of genetic factors is the most promising approach in differentiating out affective subgroups—is supported by the authors' own family history and family study data. In their patient sample, the occurrence of mania and genetic history showing two generations of affective disorder differentiate out one group of patients,