Abstract
Objective: Hikikomori, a form of severe and long-term social withdrawal, known to cause the waste of work force in society and the decrease in performance, has recently been accepted as a psychiatric disorder. After realizing the lack of assessment instruments related to this syndrome, the 25-item Hikikomori Questionnaire (HQ-25) was developed by the researchers. The aim of the study is to examine the HQ-25's adaptation to the Turkish language, its validity and reliability.
Method: The sample consists of 343 healthy participants who are not suffering from any mental or physical illnesses. HQ-25, Multidimensional Scale of Perceived Social Support (MSPSS), UCLA Loneliness Scale, and Preference for Solitude Scale (PSS) have been used.
Results: The average age of the participants was 33.15±13.56 years and 46.0% (n=159) of the participants were female. The value of Cronbach's alpha is 0.91, in the internal consistency reliability assessment of the questionnaire. According to the Exploratory Factor Analysis (EFA), the questionnaire had three sub-scales: “Socialization”, “Isolation” and “Emotional Support” (Variance description:55.67%, Kaiser-Meier-Olkin Value:0.923). The Confirmatory Factor Analysis (DFA) Assessment found that the original 3-Factor Structure of the scale was supported. It is seen that the total scale and subscale correlations are between 0.47 to 0.93. HQ-25's correlation coefficient with MSPSS, UCLA Loneliness Scale, and PSS has been calculated as r>0.30.
Conclusion: HQ-25 is a new potential self-report instrument that might help assess social isolation. As a result of our study, it has been seen that HQ-25 might be safely used in academic studies and clinical practice to assess social isolation.

Key words: Hikikomori, social isolation, questionnaire, validation, reliability