A form of severe social withdrawal, called hikikomori, has been frequently described in Japan and is characterized by adolescents and young adults who become recluses in their parents' homes, unable to work or go to school for months or years. The aim of this study was to review the evidence for hikikomori as a new psychiatric disorder. Electronic and manual literature searches were used to gather information on social withdrawal and hikikomori, including studies examining case definitions, epidemiology, and diagnosis. A number of recent empirical studies have emerged from Japan. The majority of such cases of hikikomori are classifiable as a variety of existing Diagnostic and Statistical Manual (DSM) psychiatric disorders. However, a notable subset of cases with substantial psychopathology does not meet criteria for any existing psychiatric disorder. We suggest hikikomori may be considered a culture-bound syndrome and merits further international research into whether it meets accepted criteria as a new psychiatric disorder. Research diagnostic criteria for the condition are proposed.