To the Editor Vyssoki et al1 investigated the effects of sunshine on suicide incidence and found a small yet significant positive correlation between the number of suicides and hours of daily sunshine for the day of suicide and up to 10 days prior to suicide after differencing for the effects of season, as well as a significant negative correlation between the number of suicides and daily hours of sunshine for the 14 to 60 days prior to the suicide event. These effects were found in the entire sample and in violent suicides. They analogized this finding to the recovery discrepancy between psychomotor activity and depressed mood. Nonetheless, they also recognized that the discrepancy rarely occurred. Therefore, the discrepancy seems unlikely to contribute to the very opposite significance because the rare discrepancy would be averaged out. In my opinion, the change in hours of sunshine may be a better and more reasonable variable related to suicide. If the duration of daily sunshine does contribute to suicide incidence in Austria, the suicide peak should be in summer, with substantially longer bright light exposure. However, according to Schöny et al,2 the peak suicide rate in Austria is in spring, while in August, there are fewer suicide cases than at other times.
Tsai J. Suicide Risk: Sunshine or Temperature Increase?. JAMA Psychiatry. 2015;72(6):624-625. doi:10.1001/jamapsychiatry.2014.3223