A Study in Manic-depressive Psychosis

AMONG psychotic patients the manic-depressive has probably gained most from recent advances in treatment. In spite of this improving outlook, there has been a disappointingly small increase in our understanding of the nature of the disease itself. A real contribution to this understanding is made in this report of the epidemiology of manic-depressive psychosis in a Swedish county between 1919 and 1948. All patients admitted to hospital wvith the diagnosis during the thirty-year period became the propositi, and their extended families yielded miiaterial for genetic and social study. Tlhere wvere 216 patients in the original sample (90 males and 126 females), and soime 2,000 of their relatives were investigated. Among the relatives, 72 secondary cases were found, giving "morbidity risks" of 14 per cent. among siblings, 7.5 per cent. among parents, and 17 per cent. among the children of the propositi. The total morbidity risk for manic-depressive psychosis in Sweden is about 1 per cent. No important difference was demonstrated between the occurrence of other mental disorders in this group of relatives and the general population. It is suggested tentatively that adverse environmental conditions in childhood might influence the emergence of psychosis among relatives of manic-depressives, and this is supported to some extent by the figures which are quoted. The author agrees with other writers that the mode of inheritance of manic-depressive psychosis may be through a single autosomal dominant gene and cites thirty instances of successive generation attack from his study to support this He suggests that an "incomplete manifestation" of the disease may account for the discrepancy between the expected frequency among near relatives (50 per cent.) and that found in this and other studies (about 15 per cent.). Most British geneticists would probably be more conservative in their interpretation of this data and be inclined to think in terms of multiple gene inheritance. However, there is no doubt that the interaction of environment and the weight of inherited predisposition determines to some extent the "penetrance" or degree of expression of a clinical syndrome. In 83 per cent. of the cases which were investigated the first attack wvas a depression, and it is encouraging to find that only half of all the manic-depressives in the study had more than one attack of the illness. The report does not belittle the immense technical and methodological difficulties of a retrospective enquiry of this sort, and there is a full and …