Dose Response Relationships of Loneliness and Insomnia With Subclinical Hikikomori Among College Students: A Multicentre Survey

BACKGROUND: Hikikomori, particularly among young adults, has gained growing attention. This study explored the nonlinear associations of loneliness and insomnia with subclinical hikikomori among college students. METHODS: A total of 6514 college students were assessed in this study. The University of California Los Angeles Loneliness Scale (UCLA-LS), the seven-item Insomnia Severity Index questionnaire (ISI-7), and the 1-month version of the HQ-25 (HQ-25M) were used to measure loneliness, insomnia, and subclinical hikikomori, respectively. Restricted cubic spline (RCS) models were utilized to characterize the nonlinear relationships between different measures. RESULTS: After adjusting for confounders, the RCS models revealed that loneliness and insomnia had significant nonlinear relationships with hikikomori, with both showing a dose-response pattern. A J-shaped relationship was observed between loneliness and subclinical hikikomori, with an inflection point at UCLA-LS = 50.15. Additionally, a significant nonlinear relationship between insomnia and subclinical hikikomori was also found, with an inflection point at ISI-7 = 4.08. Scores above these thresholds for UCLA-LS and ISI-7 were associated with increased risk of hikikomori. Subgroup analyzes did not reveal any significant moderating effects. Regarding the associations of loneliness and insomnia with the risk of subclinical hikikomori, the inflection points for participants with a history of psychiatric problems and perceived poor health status were lower than those in the other groups. CONCLUSIONS: Given the adverse impacts of hikikomori on college students, it is important to develop appropriate preventive and treatment strategies to address loneliness and insomnia in this vulnerable population.