Relationship between daylength and suicide in Finland

Abstract

BackgroundMany 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.MethodsThe 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.ResultsA 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.ConclusionsThe 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.

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

“…However, on the basis of these data it cannot be judged whether the finding concerned only depressed suicide cases or is a key feature of depressive disorder in general. Nevertheless, it gives support to the view that the activation of brown adipose tissue improves cold tolerance at the cost of heat tolerance, triggering anxiety and psychomotor agitation and eventually affecting mood in a negative way during the late-spring and early summer [8].…”

“…Suicide rates vary in both the short and long term [6][7][8]. Mortality from suicide may additionally vary considerably within a country [9] or in accordance with a section of the population [10].…”

Nocturnal Wakefulness Is Associated With Next-Day Suicidal Ideation in Major Depressive Disorder and Bipolar Disorder

“…PSG-assessed decreased sleep efficiency has also been associated with number of lifetime suicide attempts 10 . Other investigations have suggested that altered chronobiological activity is related to both suicidal thoughts 11 and deaths 12 . The EEG sleep literature and systematic investigations evaluating time of day effects on suicide risk are relatively sparse, however, and analyses often do not adjust for depressive symptoms or use current suicidal thoughts as an outcome measure.…”

The alcohol effect on natural chronobiological rhythms of suicidal activity in patients supervised by addiction treatment specialists and psychiatrists

“…В отличие от наших данных, например, в Фин-ляндии [11] единственный максимум суицидов при-ходится на период с 15 мая по 25 июля, т.е. он сим-метричен относительно летнего солнцестояния.…”