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

Incidence and Season of the Year

Kollibay-Uter,¹ E.Krapf,² and others have drawn attention to the fact that mental disorders in general show a yearly rhythm. That is to say they do not occur with the same frequency at every time of the year. For an examination of this point I had suffi­cient data about 116 of my propositi³ with a total of 551 separate attacks of illness. These attacks of illness arranged by month show the same phenomenon as has already been observed for mental disorders generally. The figures are conveniently arranged in the form of a curve (Table 3, Figure 3).

Broken line = Empirical values

Thick line = Corrected values

Some of the minor variations of this curve are likely to be caused accidentally; and in order to smooth out such accidental varia­tions I have calculated the corrected value for each month on the following principle, in common use: the figure for the month is doubled and to it are added the values for the two neighbouring months, and the total so obtained is divided by four. In this way the figures given in brackets have been obtained, and from them the curve represented by the thicker line. This curve shows, in good agreement with the findings of Kollibay‑Uter etc., the time of highest frequency of incidence to be in the early summer and that of lowest frequency to be in the autumn and winter.

(1) Kollibay‑Uter. Z. ges. Neurol. Psychiat. (1921), 65 : 351
(2) Krapf, E. Rev. Neur. de Buenos Aires. (1957), 2 : 107
(3) For the manner in which these propositi were selected see p.