Laura Hiltunen1, Kirsi Suominen, Jouko Lönnqvist, Timo Partonen. 1. National Institute for Health and Welfare, Department of Mental Health and Substance Abuse Services, P,O, Box 30 (Mannerheimintie 166), FI-00271 Helsinki, Finland. laura.hiltunen@thl.fi.
Abstract
BACKGROUND: Many previous studies have documented seasonal variation in suicides globally. We re-assessed the seasonal variation of suicides in Finland and tried to relate it to the seasonal variation in daylength and ambient temperature and in the discrepancy between local time and solar time. METHODS: The daily data of all suicides from 1969 to 2003 in Finland (N = 43,393) were available. The calendar year was divided into twelve periods according to the length of daylight and the routinely changing time difference between sun time and official time. The daily mean of suicide mortality was calculated for each of these periods and the 95% confidence intervals of the daily means were used to evaluate the statistical significance of the means. In addition, daily changes in sunshine hours and mean temperature were compared to the daily means of suicide mortality in two locations during these afore mentioned periods. RESULTS: A significant peak of the daily mean value of suicide mortality occurred in Finland between May 15th and July 25th, a period that lies symmetrically around the solstice. Concerning the suicide mortality among men in the northern location (Oulu), the peak was postponed as compared with the southern location (Helsinki). The daily variation in temperature or in sunshine did not have significant association with suicide mortality in these two locations. CONCLUSIONS: The period with the longest length of the day associated with the increased suicide mortality. Furthermore, since the peak of suicide mortality seems to manifest later during the year in the north, some other physical or biological signals, besides the variation in daylight, may be involved. In order to have novel means for suicide prevention, the assessment of susceptibility to the circadian misalignment might help.
BACKGROUND: Many previous studies have documented seasonal variation in suicides globally. We re-assessed the seasonal variation of suicides in Finland and tried to relate it to the seasonal variation in daylength and ambient temperature and in the discrepancy between local time and solar time. METHODS: The daily data of all suicides from 1969 to 2003 in Finland (N = 43,393) were available. The calendar year was divided into twelve periods according to the length of daylight and the routinely changing time difference between sun time and official time. The daily mean of suicide mortality was calculated for each of these periods and the 95% confidence intervals of the daily means were used to evaluate the statistical significance of the means. In addition, daily changes in sunshine hours and mean temperature were compared to the daily means of suicide mortality in two locations during these afore mentioned periods. RESULTS: A significant peak of the daily mean value of suicide mortality occurred in Finland between May 15th and July 25th, a period that lies symmetrically around the solstice. Concerning the suicide mortality among men in the northern location (Oulu), the peak was postponed as compared with the southern location (Helsinki). The daily variation in temperature or in sunshine did not have significant association with suicide mortality in these two locations. CONCLUSIONS: The period with the longest length of the day associated with the increased suicide mortality. Furthermore, since the peak of suicide mortality seems to manifest later during the year in the north, some other physical or biological signals, besides the variation in daylight, may be involved. In order to have novel means for suicide prevention, the assessment of susceptibility to the circadian misalignment might help.
Authors: Johan Reutfors; Urban Osby; Anders Ekbom; Peter Nordström; Jussi Jokinen; Fotios C Papadopoulos Journal: J Affect Disord Date: 2009-03-26 Impact factor: 4.839
Authors: Laura Hiltunen; Jari Haukka; Reija Ruuhela; Kirsi Suominen; Timo Partonen Journal: Environ Health Prev Med Date: 2014-05-03 Impact factor: 3.674
Authors: Elizabeth D Ballard; Jennifer L Vande Voort; Rebecca A Bernert; David A Luckenbaugh; Erica M Richards; Mark J Niciu; Maura L Furey; Wallace C Duncan; Carlos A Zarate Journal: J Clin Psychiatry Date: 2016-06 Impact factor: 4.384
Authors: Richard A White; Deborah Azrael; Fotios C Papadopoulos; Gavin W Lambert; Matthew Miller Journal: BMJ Open Date: 2015-06-03 Impact factor: 2.692