Stronger geomagnetic fields may be a risk factor of male suicides

Some previous studies have shown a positive relation between geomagnetic disturbances and an increased incidence of suicide. If such a relation exists, stronger geomagnetic fields may affect the number of suicides, because stronger geomagnetic fields generally cause larger geomagnetic field disturbances. Therefore, we here investigated the relation between local geomagnetic field magnetic flux density and the standardized morbidity ratios (SMR) for suicide by each prefecture in Japan.

Monthly suicide data for each prefecture in the period January 1999 to December 2008 was obtained, and it was found that a total of 216 171 male individuals and 85 154 female individuals committed suicide during this period. A multiple linear regression analysis was carried out with a backward elimination procedure. The SMR for suicide by each prefecture was taken as the response variable and the explanatory variables were each prefecture's local geomagnetic field magnetic flux density (nT), north latitude (°), monthly mean unemployment rate (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly total day length (hours). Analyses were carried out separately for each sex.

In the multiple linear regression analysis for male subjects, the local geomagnetic field magnetic flux density (nT), monthly mean unemployment rate (%), and monthly mean humidity (%) were associated with the incidence of suicide, but in the multiple linear regression analysis of female subjects, only north latitude was associated with that.

In this study, we generated a hypothesis that stronger geomagnetic fields affect the number of cases of male suicide.