A Contribution to The Aetiology of Manic-Depressive Insanity (1940)

The Relationship between Manic‑Depressive Insanity and Schizophrenia

From published data at present available, obtained by family investigations, one may say that manic‑depressive insanity shows no relationship discernible by statistical methods with any other psychosis or psychiatric abnormality, with the single exception of schizophrenia. The nature of its relationship with schizophrenia, if indeed such a relationship exists, is quite obscure. It has been asserted that schizophrenic ascendants, particularly schizophrenic parents, are especially rare for manic‑depressives, but that, on the other hand, schizophrenic children of manic‑depressives not infrequently occur. The first assertion would not appear to be justified by the material available. Röll and Entres found one schizophrenic parent (frequency 0.8%) and I found four schizophrenic parents (frequency 0.8%). These figures correspond with the fre­quency of schizophrenia in the general population (approximately 0.8%) and are only slightly greater than the frequency of schizo­phrenia in the parents of the general population (0.5%). On the other hand, the frequency of schizophrenia in the children of manic‑depressives is in the material of Röll and Entres 1.8%, in my material 3.1%. These figures are rather high, but their sta­tistical significance is not great. Veinberg and Lobstein have emphasized the frequency of schizophrenia among the nephews and nieces of their manic‑depressives and have discussed the whole problem of the relationship of the two psychoses. In their opinion, the hereditary factor for manic‑depressive psychoses exerts an activating influence on the schizophrenic factor. I made a similar suggestion in an earlier work.¹ This speculation, however, seems to be premature; for firstly, the numbers are too small to allow of any statistical certainty, and secondly, the possibility of incorrect diagnosis is not at all easily excluded. In other words, one cannot exclude the possibility that genotype and phenotype do not accurately correspond. In my material I found that the frequency of schizophrenia was much smaller when one excluded the families of propositi who showed even the slightest atypical symptoms. This could obviously be so interpreted that the presence of a schizophrenic factor expresses itself in the atypical colouring of a supervening manic‑depressive psychosis.

(1) Proc. Roy. Soc. Med. (l936). 26.