Mental disorders and suicide in Japan: a nation-wide psychological autopsy case-control study

The purpose of the present nationwide psychological autopsy case-control study is to identify the association between mental disorders and suicide in Japan, adjusting for physical conditions.

A semi-structured interview was conducted of the closest family members of 49 suicide completers and 145 gender-, age-, and municipality-matched living controls. The interview included sections of socio-demographic characteristics, physical conditions, and a psychiatric interview producing DSM-IV diagnoses of mental disorders prior to suicide (or at survey). We compared prevalences of mental disorders between the two groups, using conditional logistic regression.

A significantly higher proportion with any mental disorder was found in the suicide group (65.3%) compared to the control group (4.8%) (p=0.003, odds ratio [OR]=7.5). The population attributable risk proportion associated with mental disorder was 0.24. Mood disorder, particularly major depressive disorder, was the most strongly associated with suicide (p<0.001). Anxiety disorder, alcohol-related disorder, and brief psychotic disorder were also significantly associated with suicide (p<0.05). These patterns were unchanged after adjusting for serious chronic physical conditions.

The present study had some limitations, such as small sample size, sampling bias and information bias.

Most mental disorders, particularly mood disorder, were significantly associated with a greater risk of suicide in Japan, independent of physical conditions. Mental disorders are a major target of suicide prevention programs in Japan.