Hikikomori (literally "pulling away, being confined," i.e., "acute social withdrawal") is a Japanese term to refer to the phenomenon of reclusive adolescents and young adults who have chosen to withdraw from social life, often seeking extreme degrees of isolation and confinement due to various personal and social factors in their lives. The term "Hikikomori" refers to both the sociological phenomenon in general as well as to individuals belonging to this societal group. The term was originated in Japan but is in no way exclusive to the culture. For example, some youths in the USA have dubbed themselves "American Hikikomori".

Hikikomori was first recognized in the early 1990s. One million Japanese, or almost 1 percent of the population, are estimated to suffer from Hikikomori, defined as a withdrawal from friends and family for months or even years. Some 40 percent of Hikikomori are below the age of 21.

Western psychologists compare Hikikomori with social anxiety and agoraphobia. The affliction has also been likened to Asperger's syndrome, a mild variant of autism.

Yuichi Hattori, M.A., a psychologist currently treating 18 patients with the disorder, believes that Hikikomori is caused by emotionally neglectful parenting. Hattori argues that none of his patients had been sexually or physically abused, yet they all show signs of posttraumatic stress disorder.

"Hikikomori looks more to me like an extreme case of social anxiety," says David Kupfer, Ph.D., a psychologist with a private practice in Virginia. Emotionally unresponsive parents are only one of the factors involved in the development of this disorder, says Kupfer.

The Japanese Ministry of Health defines Hikikomori as individuals who refuse to leave their parents' house, and isolate themselves away from society and family in a single room for a period exceeding six months. While the distinctiveness of the phenomenon varies depending on the individual, some youths remain in isolation for years, or in rare cases, decades. Often Hikikomori start out as school refusals.