Computers, video games, and technological devices are part of young people’s everyday lives. Hikikomori is a Japanese word describing a condition that mainly affects adolescents or young adults who live isolated from the world, cloistered within their parents’ homes, locked in their bedrooms for days, months, or even years on end, and refusing to communicate even with their family. These patients use the Internet profusely, and only venture out to deal with their most imperative bodily needs. Although first described in Japan, cases have been described from around the world. This is the first published report from Canada. The disorder shares characteristics with prodromal psychosis, negative symptoms of schizophrenia, or Internet addiction, which are common differential or comorbid diagnoses. However, certain cases are not accompanied by a mental disorder. Psychotherapy is the treatment of choice although many cases are reluctant to present. The exact place of hikikomori in psychiatric nosology has yet to be determined. We searched Medline up to 12th May, 2015 supplemented by a hand search of the bibliographies of all retrieved articles. We used the following search terms: Hikikomori OR (prolonged AND social AND withdrawal). We found 97 potential papers. Of these 42 were in Japanese, and 1 in Korean. However, many of these were cited by subsequent English language papers that were included in the review. Following scrutiny of the titles and abstracts, 29 were judged to be relevant. Further research is needed to distinguish between primary and secondary hikikomori and establish whether this is a new diagnostic entity, or particular cultural or societal manifestations of established diagnoses.

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Asymmetry between the left and right brain is a key feature of brain organization. Hemispheric functional specialization underlies some of the most advanced human-defining cognitive operations, such as articulated language, perspective taking, or rapid detection of facial cues. Yet, genetic investigations into brain asymmetry have mostly relied on common variant studies, which typically exert small effects on brain phenotypes. Here, we leverage rare genomic deletions and duplications to study how genetic alterations reverberate in human brain and behavior. We quantitatively dissected the impact of eight high-effect-size copy number variations (CNVs) on brain asymmetry in a multi-site cohort of 552 CNV carriers and 290 non-carriers. Isolated multivariate brain asymmetry patterns spotlighted regions typically thought to subserve lateralized functions, including language, hearing, as well as visual, face and word recognition. Planum temporale asymmetry emerged as especially susceptible to deletions and duplications of specific gene sets. Targeted analysis of common variants through genome-wide association study (GWAS) consolidated partly diverging genetic influences on the right versus left planum temporale structure. In conclusion, our gene-brain-behavior mapping highlights the consequences of genetically controlled brain lateralization on human-defining cognitive traits.