Seasonal Variation in Suicidal Deaths in Chile: Its Relationship to Latitude

Abstract

Background: Studies in the northern and southern hemispheres consistently identified seasonal influences on monthly and semester suicide distribution. The variations of sunlight exposure in zones of increasing latitude has been suggested as one of the most plausible explanations for this phenomenon. Some recent studies in the northern hemisphere could not find seasonal asymmetries of suicides. The current study examines the monthly, seasonal and semester distribution of suicidal deaths in Chile and the influence of seasons in zones of low latitude as compared with regions of high or very high latitude, trying to determine if a seasonal pattern still exists in a country of the southern hemisphere. Methods: Monthly, seasonal and semester suicidal data over the period 1995–1999 were examined for the whole sample and for gender-specific subgroups in Chile. Four different latitudinal zones were analyzed separately, in order to investigate the effect of the photoperiod on suicide distribution. Results were analyzed by χ² tests for multinomials, as an overall measure of deviation. Results: We found a significant unimodal springtime peak for both genders in the global territory. Among the 4,710 male and 829 female suicides reported in this period there were no gender differences in the seasonal pattern of suicidal deaths. When divided into four different latitudinal zones, the regions with low latitude (north of the country) showed no significant differences, while central and southern zones (higher latitude) show a significant springtime pattern. In the extreme south of the country, no significant differences were found, probably due to the very small number of cases. Conclusion: The study confirms the existence of a unimodal springtime peak of suicides in Chile, but not in the zone of low latitude. Results support the notion that the seasonal impact on suicidal distribution is a function of photoperiod.

Association of geomagnetic disturbances and suicides in Japan, 1999–2010

“…1c, d). These results correspond with previous reports showing the number of suicides to increase in spring [5][6][7]. We identified a relationship between geomagnetic disturbance and male suicides.…”

“…Risk factors associated with completed suicides have been identified, such as psychiatric illness, hopelessness, previous suicide attempts, being widowed or divorced, living alone, having a recent adverse event, having severe anxiety, having a chronic medical illness, and having a family history of suicide attempts or completions [2]. There have been some reports that environmental factors, such as electromagnetic fields [3,4], latitude [5,6], and season [5][6][7] were associated with suicides.…”

Einfluss von natürlichen Lithiumsalzvorkommen auf die Suizidmortalität in Chile 2000–2009: Eine geographische Analyse

“…Frühere Studien aus Chile, die gezeigt haben, dass die saisonale Variabilität an Suizidinzidenz in Regionen mit zunehmender geographischer Breite -und daher auch weiter entfernt von Atacama -größer ist [16], stimmen mit der Literatur über Zusammenhän-ge zwischen Sonnenlicht und Suizidmortalität überein [31]. So ändert sich der Einfallswinkel und die Dauer der Insolation pro Tag je nach Breitengrad und nimmt mit der Entfernung vom Äquator ab.…”

“…Es scheint plausibel, dass die niedrigere saisonale Variabilität der Suizidmortalität im Norden Chiles auch dem bekannten stimmungsstabilisierenden und antisuizidalen Effekt von Lithium geschuldet sein könnte [16]. Allerdings muss in Betracht gezogen werden, dass die Amplituden suizidaler Saisonalität in Regionen mit niedrigen Suizidraten aus statistischen Gründen eher gering sind -wie schon in der Literatur beschrieben [34].…”

“…Chile ist mit seinem zusammenhängenden Kutur-und Sprachraum mit gemeinsamer Juridikatur trotz ausgeprägter NordSüd-Ausdehnung und seinen nach einheitlichen Erhebungsmethoden durch ein nationales Statistikamt zentral gesammelten Suizidmortalitätsdaten eine interessante Region für Untersuchungen. Dies gilt insbesondere für die Epidemiologie der Suizidmortalität, aber auch im Hinblick auf die Untersuchung von Expositionseffekten durch natürliche Lithiumsalzvorkommen [12][13][14][15][16].…”