Epidemiology of Hikikomori: A systematic review and meta-analysis of 19 studies

Aim: Hikikomori, a severe form of social withdrawal, has been recognized as an important global public health problem. However, estimates of the worldwide Hikikomori prevalence have been inconsistent. This study aimed to provide a comprehensive assessment of the cross-cultural prevalence of Hikikomori through a meta-analysis and systematic review. Methods: We systematically searched multiple databases (including PubMed, EMBASE, PsycINFO, and Web of Science) for relevant studies. Pooled prevalence estimates were calculated using a random-effects model. Subgroup analyses for categorical variables and meta-regression analyses for continuous variables were performed to identify potential moderators of Hikikomori prevalence estimates. Results: A total of 19 studies based on 58,229 participants were included for analysis. The overall prevalence of Hikikomori was 8.0% (95% CI, 4.9%–12.9%). The prevalence of Hikikomori did not differ significantly between regions (East Asia and Western), time periods (pre– and post–COVID-19 pandemic), sex, sample size, or presence versus absence of psychiatric disorders. In contrast, higher prevalence rates were reported in studies using the 25-item Hikikomori Questionnaire (HQ-25) (21.7%; 95% CI, 11.8%–36.4%) versus other questionnaires (5.0%; 95% CI, 3.1%–7.9%, [P < 0.01]) and nonprobability sampling (12.5%; 95% CI, 7.9%–19.2%) versus probability sampling methods (3.1%; 95% CI, 1.4%–6.9% [P < 0.01]). Lower study quality (coefficient = −0.45, P = 0.03) and older age were also linked to higher prevalence (coefficient = 0.10, P = 0.01). Conclusion: This meta-analysis suggests that Hikikomori is a common problem globally. The results highlight the importance of using standardized diagnostic tools as well as further research on moderating factors and intervention methods to alleviate disabling experiences associated with Hikikomori.