Hikikomori: psychopathology and differential diagnosis of a condition with epidemic diffusion

Objective: Hikikomori, from the Japanese words ‘hiku’ (to pull) and ‘komoru’ (to withdraw), is a clinical condition in which a subject locks himself/herself into his/her own house for more than 6 months. This condition is becoming relevant in Japan and other Asian countries, with new cases emerging in Europe and a steep increase in its incidence. Methods: In this article, the various psychopathological and diagnostic hypothesis and the different criteria proposed by the various authors have been analysed and compared, paying attention also to the new studies conducted in Europe and to therapeutic perspectives that are opening up for its treatment. Results: Numerous hypothesis have been put forward for the genesis of hikikomori, in particular, the hypothesis of a behaviour seen as a dysfuncion of the family system or as a result of our current modern society. Furthermore, this behaviour has been compared to other conditions such as internet addiction and a specific form of depression called Modern Type Depression (MTD). Conclusions: Hikikomori could represent the clinical answer to a social evolution, similarly to other phenomena such as binge behaviours and use of psychoactive substances. Further studies are needed to clarify diffusion, diagnosticassessment and differential diagnosis.Key points Hikikomori is now considered a contemporary society-bound syndrome linked to modern society changes. Hikikomori might be a coping strategy to avoid relationships, social judgement and possible failures. Hikikomori might represent an extreme suffering that needs to be identified early: it is linked to severe form of modern type depression and it is a risk factor for suicidal behaviours. It is important to inform and sensitise communities about hikikomori to assure early interventions. More clinical studies are needed to define a unitary and specific model of hikikomori and to structure focussed interventions.