Suicide Season:

Subject: Suicide rates increase by 2,000% from February until May then sharply decrease during the summer back to the February low.

I recently came across a chart of seasonal variations in suicide rate.[1] Suicide rates vary dramatically from season to season. Fewer people kill themselves in January and February than any other month. But from February to May the numbers rise steadily. Suicide rates peak in May about 20 times higher than February's low. From May they drop steadily and by July they are about about the same as February. A second rise in rates occurs from September to October but only about 1/3 as high as May's peak.

What is behind this?

This appears to be a global phenomena. Researchers have been wondering about this. I have found studies examing seasonal and other variables which affect suicide rates from all over the world. Australia [2] , Canada [3] , Alaska [ 4], Chile[5], Mongolia [6], China [7] , Italy [8] , France [9] and Britain [10] all show strong seasonal variability. Data from the Southern Hemisphere differs only in that the peak is during their Springtime, not ours.

Several different environmental factors also appear to change suicide rates. Extremes in either temperature or barometric pressure increased suicides according to a study from Inner Mongolia.[11] A Canadian study found that the elderly are more sensitive to variations from normal temperature while younger people respond to the season without regard to the weather.[12] Men tend to have only the single yearly Spring peak in suicides while women have two peaks in suicides a year, Spring and Fall.[13]

The clearest suicide trigger though is the increasing daylight in the Spring. As we approach the Spring Equinox and Summer Solstice and daylight lasts longer, suicide rates skyrocket. Time of day is also a factor. A Dutch study which plotted time of suicide against time and hours of daylight found a significant correlation between suicide times and the light dark cycle.

'.... suicide rates at night drop to about 10% of their daytime values. Second, there are two daily peaks in the patterns which shift their timing over the year, with one peak occurring shortly after sunset, and the other one consistently occurring 9-10 h[hours] earlier. Both peaks shift with the 5.5-h shift in sunset time....'[14]

This information goes against everything I would have guessed. If quizzed, I would have guessed that rates would be peak in the gloomy, winter days when Seasonal Affective Disorder is at it's darkest, not the bright Spring days .

What should we do with this information? Theoretically the severely depressed should all migrate to the Southern Hemisphere each Spring to avoid suicide. Perhaps, simply understanding this Spring surge exists might help those contemplating the act to not take themselves so seriously. People want to think that their feelings, their depressions and the choice of suicide have to do with their life circumstances. In truth it may only be the weather, the time of day, or more likely the time of year that prompts one to contemplate ending their life.

References:
1. Manic Depressive Illness by Frederick Goodwin and Kay Jamison, copyright 1990, Oxford University Press, Inc
2. Cantor CH, Hickey PA, De Leo D. Seasonal variation in suicide in a predominantly Caucasian tropical/subtropical region of Australia.Psychopathology 2000 Nov-Dec;33(6):303-6
3. Marion SA, Agbayewa MO, Wiggins S.The effect of season and weather on suicide rates in the elderly in British Columbia. Can J Pub Health1999 Nov-Dec;90(6):418-22
4. Kettl PA, Collins T, Sredy M, Bixler EOSeasonal differences in suicide birth rate in Alaska Natives compared to other populations. Am Indian Alsk Native Ment Health Res 1997;8(1):1-10
5. Retamal P, Humphreys D. Occurrence of suicide and seasonal variation. Rev Saude Publica 1998 Oct;32(5):408-12
6. Wang YT, Wang D, Wang XY. Suicide and meteorological factors in Huhhot, Inner Mongolia.1997;18(3):115-7
7. Zhang J Suicides in Beijing, China, 1992-1993. Suicide Life Threat Behav 1996 Summer;26(2):175-80
8. Micciolo R, Williams P, Zimmermann-Tansella C, Tansella M. Geographical and urban-rural variation in the seasonality of suicide: some further evidence J Affect Disorc 1991 Jan;21(1):39-43
9. Souetre E, Salvati E, Belugou JL, Douillet P, Braccini T, Darcourt G. Seasonality of suicides: environmental, sociological and biological covariations.J Affect Disord 1987 Nov-Dec;13(3):215-25
10. Meares R, Mendelsohn FA, Milgrom-Friedman J. A sex difference in the seasonal variation of suicide rate: a single cycle for men, two cycles for women. Br J Psychiatry 1981 Apr;138:321-5
11. Wang YT, Wang D, Wang XY
12. Marion SA, Agbayewa MO, Wiggins S.
13. Meares R, Mendelsohn FA, Milgrom-Friedman J. A sex difference in the seasonal variation of suicide rate: a single cycle for men, two cycles for women. Br J Psychiatry 1981 Apr;138:321-5
14. van Houwelingen CA, Beersma DG. Seasonal changes in 24-h patterns of suicide rates: a study on train suicides in The Netherlands. J Affect Disord 2001 Oct;66(2-3):215-23