Development and validation of the 25-item Hikikomori Questionnaire (HQ-25).

Aim: Hikikomori, a form of severe social withdrawal, is an emerging issue in mental health, for which validated measurement tools are lacking. The object was to develop a self-report scale of hikikomori, and assess its psychometric properties and diagnostic accuracy.

Methods: A sample of 399 participants from clinical and community settings completed measures. Psychometric properties were assessed with factor analysis; diagnostic accuracy was compared against a semi-structured diagnostic interview.

Results: The Hikikomori Questionnaire contained 25 items across three subscales representing socialization, isolation, and emotional support. Internal consistency, test-retest reliability, and convergent validity were all satisfactory. The area under the curve was 0.86 (95% confidence interval, 0.80-0.92). A cut-off score of 42 (out of 100) was associated with a sensitivity of 94%, specificity of 61%, and positive predictive value of 17%.

Conclusion: The 25-item Hikikomori Questionnaire (HQ-25) possesses robust psychometric properties and diagnostic accuracy in an initial sample of Japanese adults. Additional research on its psychometric properties and ability to support clinical assessment of hikikomori is warranted.