Exploring lag and duration effect of sunshine in triggering suicide.
BACKGROUND
Sunshine is considered to have a beneficial impact on mood. Interestingly, it has been consistently found that the incidence of suicide reaches a peak during early summer.


METHODS
In order to explore the pattern of sunshine and suicide risk in a time frame of up to nine days and investigate possible lag and duration parameters of sunshine in the triggering of suicide, Greek daily suicide and solar radiance data were analyzed for a 10-year period using logistic regression models.


RESULTS
The solar radiance during the day before the suicide event was significantly associated with an increased suicide risk (OR=1.020 per MW/m2). The average solar radiance during the four previous days was also significantly associated with an increased suicide risk (OR=1.031 per MW/m2). Differences among genders include the longer sunshine exposure needed in males to trigger suicide, compared to females and a lag period of three to four days that was found to lapse in females till the suicide. The increase in suicide risk in June compared to December, attributable to the daily sunshine effect, varies from 52% to 88%, thus explaining the already known suicide monthly seasonality.


CONCLUSIONS
No individual data on solar radiance exposure, mental disorders, alcohol consumption or suicide method were available.


CONCLUSIONS
The effect of sunshine in the triggering of suicide may be mediated through a mechanism with a specific lag and duration effect, during the nine days preceding suicide. We hypothesize that sunshine acts as a natural antidepressant which first improves motivation, then only later improves mood, thereby creating a potential short-term increased risk of suicide initially upon its application.
Papadopoulos
Fotios C
FC
Department of Hygiene and Epidemiology, Athens University Medical School, 75 M. Asias Str., Goudi, P.O. Box 11527, Athens, Greece. fotis.papadopoulos@gmail.com
Frangakis
Constantine E
CE
Skalkidou
Alkistis
A
Petridou
Eleni
E
Stevens
Richard G
RG
Trichopoulos
Dimitrios
D
D000339:Affect; D006115:Greece / Q000453:epidemiology; D006801:Humans; D017440:Photoperiod; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D013405:Suicide / Q000523:psychology / Q000706:statistics & numerical data*; D013472:Sunlight; D013997:Time Factors