Abstract
BACKGROUND: Currently, paradoxical findings exist regarding the level of functioning in individuals with Hikikomori (prolonged social withdrawal). AIMS: This systematic review aimed to clarify the functioning, disability, and health of individuals with Hikikomori and their families in comparison to those without Hikikomori. METHOD: Relevant studies were searched from April 22 to 25, 2022, using MEDLINE, PsycINFO, Scopus, and two Japanese databases. Functions were categorized into 'body functions"; "structure"; and "activity and participation', which were further classified into subcategories. RESULTS: Of the 8,181 studies screened, 24 studies with 1,769 individuals with Hikikomori were included. Twelve, three, and four indicators from six studies on depression and anxiety, three on addiction, and two on thought problem symptoms, respectively, were higher in the Hikikomori group than in the comparison group, with at least moderate effect sizes. Three indicators from three studies on interpersonal relationships were worse in the Hikikomori group, with at least moderate effect sizes. The meta-analyses showed that internalizing symptoms, externalizing symptoms, and thought disorders were significantly higher in the Hikikomori group than those in the comparison group with moderate-to-high effect sizes. Contrastingly, communication/interpersonal interactions were significantly lower in the Hikikomori group than those in the comparison group. No significant differences were observed in daily life/social life and the families' communication/interpersonal interactions and relationship. CONCLUSIONS: The study limitations include a high risk of bias and heterogeneity. Overall, individuals with Hikikomori often have impaired mental and interpersonal interaction functions; thus, comorbidities of this condition should be carefully assessed. PROSPERO: CRD42022320592.