Time trends in method-specific suicide rates in Japan, 1990–2011

Little is known about whether particular suicide methods have contributed differently to the recent unfavourable suicide mortality trends in Japan. Analysing such trends may shed light on the effect of potentially preventable factors, such as the impact of restricting access to certain popular suicide methods, on overall rates. Therefore, we assessed recent trends in method-specific suicide by gender and age in Japan. Suicide mortality and population data between 1990 and 2011 were obtained from the Vital Statistics of Japan and used to calculate method-specific mortality rates. Suicide methods were divided into seven groups: overdose, gases, hanging, drowning, cutting, jumping and other means. Age was divided into four groups: 15-24, 25-44, 45-64 and 65+ years. We applied joinpoint regression to the data and quantified the observed changes. The results of the joinpoint regression analyses showed a sharp increase in overall suicide rates for males and females of all ages until the late 1990s. Suicide from hanging and jumping, in particular, contributed to this increase. After 2000, an increasing trend in overall suicide rates in both males and females aged 15-24 and 25-44 years was observed, with overdose, gases and hanging contributing to this increasing trend. Our findings revealed that different suicide methods varied in their contribution to the recent overall suicide transition in Japan. Regarding factors associated with the recent increase in suicides by overdose, gases, hanging and jumping, further research is needed in order to promote and implement effective means restriction strategies.