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Seasonal variation in suicides: hidden not vanished

GGz Eindhoven, PO Box 909, 5600 AX Eindhoven, The Netherlands

D. G. M. Beersma

Department of Psychiatry and Zoological Laboratory, University of Groningen, PO Box 14, 9700 AA Haren, The Netherlands

EDITED BY MATTHEW HOTOPF

Yip et al (2000) demonstrated that, in England, the seasonal variation in suicide rates in the 1980s and 1990s decreased considerably when compared with that in the 1960s and 1970s. From monthly suicide frequencies, they concluded that current data hardly show any seasonal effects on suicide rates, and they predicted that seasonal variation in suicide rates would disappear completely in the years to come.

Although we fully agree with Yip et al (and several other authors) that there is a global decline in the amplitude of seasonal variation in suicide rate, we do not agree with the conclusion that seasonal influences are beginning to fade away. We came to this conclusion by a recent study of train suicides (i.e. suicide by jumping before a moving train) in The Netherlands (van Houwelingen & Beersma, 2001). In this study (n=30) we confirmed the absence of a seasonal pattern in suicide rates as observed in 28-day intervals. We did, however, observe a strong seasonal influence on 24-hour patterns. Whereas the winter season showed two daily peaks in suicide rates, at around 9-11 am and 7-10 pm, the summer season revealed one major peak around 12-4 pm and a smaller peak shortly before midnight. The timing of the major summer peak is in the trough between the two winter peaks.

This more subtle influence of time of year on suicide rates adds a different dimension to what has been considered seasonality in suicidal behaviour and may generate new ideas concerning relevant factors involved. In train suicide data, seasonal influences are clearly present. This may also be true of other methods of suicide. In order to see this, time of day and time of year have to be taken into account simultaneously.

REFERENCES

van Houwelingen, C. A. J. & Beersma, D. G. M. (2001) Seasonal changes in 24-h patterns of suicide rates: a study on train suicides in The Netherlands. Journal of Affective Disorders, in press.

Yip, P. S. F., Chao, A. & Chiu, C. W. F. (2000) Seasonal variation in suicides: diminished or vanished. Experience from England and Wales, 1982-1996. British Journal of Psychiatry, 177, 366-369.[Abstract/Free Full Text]

This Article Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Houwelingen, C. A. J. v. Articles by Beersma, D. G. M. Search for Related Content PubMed Articles by Houwelingen, C. A. J. v. Articles by Beersma, D. G. M.