Validation of the German version of the 25-item hikikomori questionnaire 25

The 25-item Hikikomori Questionnaire (HQ-25) is an instrument developed to measure a condition characterized by extreme social withdrawal that was first described in Japan. This study aimed to translate the HQ-25 into German and validate the German version (HQ-25-G).

Translation was conducted according to established guidelines. Validation was based on data from a quota sample of individuals living in Germany, ranging from 18 to 74 years old (representing the distribution of age, sex and federal state, n = 5000). Data collection occurred during August and September 2023. We tested reliability, construct validity and concurrent validity. Moreover, HQ-25 scores for key sociodemographic group were reported.

Internal reliability for the HQ-25-G was excellent (Cronbach's alpha = 0.93). We confirmed the original three-factor model. Moreover, higher hikikomori levels were significantly associated with more depressive symptoms (r = 0.50), more anxiety symptoms (r = 0.45), higher loneliness levels (r = 0.56), higher levels of objective social isolation (r = -0.47), higher levels of perceived social isolation (r = 0.59) and a higher preference for solitude (r = 0.45).

In a large population-based sample (including younger adults, middle-aged adults and older adults), the HQ-25-G version proves to be a psychometrically robust instrument, which is useful for further exploring the phenomenon of hikikomori within the German-speaking population.