A serious form of social withdrawal, initially described within Japan as hikikomori, has received increasing attention from the international scientific community during the last decade. The 25-item Hikikomori Questionnaire (HQ-25) was initially developed and validated in Japan. To date, data on its psychometric properties in other populations where cases of hikikomori have been described are still scarce. Thus, the aims of this study were to (1) translate, adapt, and validate the Italian version of the HQ-25 analyzing its psychometric properties; and (2) verify the association between hikikomori and personality functioning, social support, and problematic Internet use. A sample of 372 Italian adults aged 18 to 50 years completed the HQ-25 and measures of psychoticism, personality dysfunction, social support, and problematic Internet use were employed to test the convergent validity of the HQ-25. The data showed a satisfactory fit for a three-factor model, significantly better than a one-factor model. The three factors (socialization, isolation, and emotional support, as in the original study on the HQ-25) correlated positively with psychoticism, personality dysfunction, and problematic Internet use, and correlated negatively with social support. A lifetime history of hikikomori was present in 1.1% of the sample (n = 4). This is the first study to use the Italian validated version of the HQ-25 with an adult population. The findings from this study provide evidence of the satisfactory psychometric properties of the Italian version of the HQ-25 and support further investigation of the HQ-25 as an instrument to help screen for and investigate the presence of hikikomori.
Keywords: mental health; psychiatry; social avoidance; social detachment; social isolation.