The relationship between suicide and five climate issues in a large-scale and long-term study in Japan

Suicide rates in Japan were high in 1998 and have remained high since then. Many researchers have discussed the current state of suicide in Japan and the world; however, there are various opinions about the relationship between suicide and climate.

In the present study, we report on long-term data of suicide and examine five climatic issues in Japan as a whole and in 10 selected prefectures: the five with the highest suicide rates in 2006 (Akita, Iwate, Shimane, Yamagata and Miyazaki Prefectures) and the five with the lowest (Nara, Tokushima, Okayama, Kanagawa and Kyoto Prefectures).

Annual age-adjusted suicide rates were found to have a significant inverse correlation with annual mean air temperature in the five prefectures with the highest suicide rates and in the three prefectures with the lowest suicide rates among women. Annual age-adjusted suicide rates were significantly correlated with annual mean relative humidity in the three prefectures with the highest suicide rates among women and with the annual total sunshine duration in the three prefectures with the highest suicide rates among women.

It is important that these associations between suicide and climatic factors be discussed further from various viewpoints, including those of many researchers and relevant organizations.