Résumé
Background: Hikikomori, a severe and often prolonged social withdrawal observed primarily in young people, was first described in Japan, but cases have now been reported in many other countries. Methods: A review paper on hikikomori has been prepared following the literature searches in 3 databases. Search terms related to hikikomori included epidemiology, globalization, diagnosis, treatment, comorbidity, and COVID-19. Conclusions: Hikikomori was first reported in Japan and has been described in detail by researchers there, but there are now reports in many countries of hikikomori-like cases. It occurs primarily in young people, often men in their late teens and early twenties who isolate themselves, sometimes confining themselves to their homes for months or even years. It has been proposed that hikikomori has increased in recent years in part because of advances in information technology that result in decreased socialization. Hikikomori was originally considered a non-psychotic phenomenon, but comorbidity with psychiatric disorders is often present and should be considered during diagnosis. Considerable efforts have been made in recent years to establish reliable, widely applicable guidelines for the diagnosis and treatment of hikikomori. There is very little information with regard to neurobiology, although involvement of the immune system, oxidative stress, and the social brain network has been proposed. It is widely agreed that hikikomori must be treated in a multi-dimensional fashion, with family support very important. Lessons learned from these treatment approaches are relevant to the potential increased risk of social withdrawal arising from COVID-19 pandemic lockdowns.