Impact of Meteorological Parameters on Suicide Rates: A Case-Crossover Study in Southern Germany

Abstract

Background. Researchers worldwide reported a seasonal pattern of suicides with peaks in spring and early summer; however, only a limited number of studies has investigated the association of meteorological variables and suicides.Methods. Daily suicides (N=10,595) and meteorological data from 1990 to 2006 were available for four Bavarian cities and ten counties. Immediate, delayed and cumulative effects of air temperature, sunshine duration, cloud cover, relative humidity as well as precipitation on suicide rates were analyzed using a confounder-adjusted time-stratified case-crossover approach. Potential effect modifiers were specific weather conditions, personal or regional characteristics, and season.Results. A 5°C increase in air temperature was associated with a 4.1% (95%-confidence interval: 0.97; 7.4%) and 5.1% (2.0; 8.4%) higher suicide risk on the same day and with a delay of one day, respectively. Further, the suicide risk was 6.2% (0.6; 12.2%) higher on days with low/medium cloud cover (0-6 oktas) compared to days with high cloud cover (7-8 oktas). Temperature effects with a lag of one day were more pronounced in individuals older than 65 years (9.9% (4.3; 15.8%)). While temperature was not associated with suicides in spring we found positive associations in summer, autumn, and winter. The effects of cloud cover were strongest in summer and autumn and on days with air temperature above the median (>8.8°C). The other meteorological variables were not significantly associated with suicide.Discussion. We found a higher risk for suicides in association with short-term increases in air temperature and on days with low to medium cloud cover. This may highlight time periods when people are more likely to commit suicide.