The epidemiology of "hikikomori" (acute social withdrawal) in a community population is not clear, although it has been noted for the past decade in Japan. The objective of this study is to clarify the prevalence of "hikikomori" and to examine the relation between "hikikomori" and psychiatric disorders. A face-to-face household survey was conducted of community residents (n = 4134). We defined "hikikomori" as a psychopathological phenomenon in which people become completely withdrawn from society for 6 months or longer. We asked all respondents whether they had any children currently experiencing "hikikomori". For respondents aged 20-49 years old (n =1660), we asked whether they had ever experienced "hikikomori". A total of 1.2% had experienced "hikikomori" in their lifetime. Among them, 54.5% had also experienced a psychiatric (mood, anxiety, impulse control, or substance-related) disorder in their lifetime. Respondents who experienced "hikikomori" had a 6.1 times higher risk of mood disorder. Among respondents, 0.5% currently had at least one child who had experienced "hikikomori". The study suggests that "hikikomori" is common in the community population in Japan. While psychiatric disorders were often comorbid with "hikikomori", half of the cases seem to be "primary hikikomori" without a comorbid psychiatric disorder. (C) 2008 Elsevier Ireland Ltd. All rights reserved.