It is well known that childhood adversities (CAs) are a significant risk factor for mental disorders in later life. However, it is uncertain whether a similar association between CAs and mental disorders can be found in Japan. Few studies have employed an appropriate statistical model that takes into account the high comorbidity of CAs. The purpose of this study is to elucidate the association between CAs and the onset of mental disorders in Japan. We used the data from the World Mental Health Japan, 2002-2004 (n= 1722). Respondents completed diagnostic interviews (the World Health Organization Composite International Diagnostic Interview) that assessed lifetime prevalence of 15 Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) disorders. Associations of 12 retrospectively reported CAs with the lifetime prevalence of mental disorders were estimated using discrete-time survival analysis. Of the study sample, 32% reported as having experienced at least 1 CA during childhood. The studied CAs were highly comorbid. Parental mental illness showed significant sub-additive effects. The presence of 3 CAs showed a significant interactive effect on any mental health disorder. The number of CAs had a strong interactive effect on the onset of anxiety disorders. Predictive effects of CAs were found only among childhood onset mental disorders. It was confirmed that CAs are one of predictors of the onset of DSM-IV mental disorders, especially during childhood, in Japan. © 2010 Elsevier Ltd.