Suicide is a serious problem all over the world. Approximately 1 million people are estimated to commit suicide per year [1
]. Recent figures also show that more than 30,000 people commit suicide each year in Japan. Several epidemiologic studies [2
] have indicated risk factors for suicide, such as depression, severe anxiety, substance abuse, poor interpersonal relationships including social isolation, inability to maintain a job, anhedonia, somatic diseases, financial problems, and personal or familial history of suicide.
These suicidal risk factors can be divided broadly into two categories, personal and social factors. The former are, for example, mental disorders, including genetic vulnerability (familial history of suicide), physical disorders, and psychological isolation. The latter include socio-economic or familial factors, such as divorce, unemployment, and stressful life events. It can be assumed that the interactive effects of these two factors may attenuate personal tolerance against stressors and lead him/her to suicide. Kaplan and Sadock [9
] show 13 major suicidal risk factors ranked according to their association with suicide. Alcohol dependence, prior suicidal behavior, depression, unemployed or retired, single, widowed, and divorced are included. These factors can be clearly defined independent of the study designs. The other factors except age and race, such as irritation, loss of physical health, or unwilling to accept help, are conceptually obscure; that is, they are likely to be defined differently by each epidemiologic study design and to be affected by the value system in each country with different cultural backgrounds.
To establish an effective suicide prevention model, the strength of association between those risk factors and completed suicide should be estimated by an appropriate statistical method. Meta-analysis is a useful statistical method in this regard. However, the commonly evaluated risk factors should be included in this analysis, because the combined effect of differently defined factors on suicide is difficult to determine.
As an effective method for identifying the risk factors associated with completed suicide, psychological autopsy is one of the most valuable research tools. Usually, face-to-face structured interviews or semi-structured interviews with family members of suicide victims or their next of kin are conducted in detail, with informed consent obtained beforehand. Sometimes, their close friends, sweethearts, supervisors, and doctors can be subjects for interview. In some cases, several months are needed for the interview period, during which the time for curing the bereaved families is included.
This retrospective approach of psychological autopsy can be given an epidemiologic case-control design by using appropriate controls. The selection of control subjects usually depends on the purpose of the study. Usually, accident victims (e.g., traffic accidents) or cases of natural death are compared with the suicide victims. This study design has come into wide use in Western and Oceanian countries, China or Taiwan in Asia. However, to our knowledge, no psychological autopsy studies have been conducted in Japan thus far. In order to gain reliable evidence, such a study should be widely conducted in Japan as well as overseas. Although social factors affected by the different cultural characteristics are difficult to compare to one another, it is necessary to provide basic information of relevant suicidal risk factors for promoting future Japanese psychological autopsy studies. For this purpose, the accumulated evidence regarding the commonly defined factors in the foreign psychological autopsy studies should be clearly summarized by the appropriate statistical method.
From this point of view, the aim of the present article is to review and evaluate associations between suicidal risk factors that are cross-culturally defined and completed suicide, based on the reports that use the method of psychological autopsy with case-control study design.