In the Kawasaki case, local mental health officials told reporters that the attacker, Ryuichi Iwasaki, 51, was a hikikomori who had not worked for “a long period of time.” He was living with an aunt and an uncle who officials said did not “want to irritate him much.”



Although there have been other high-profile violent crimes involving hikikomori — in which they killed family members, or parents killed adult children who had lived as recluses for years — the correlation is still rare.

“In the past 20 years, the number of hikikomori who have committed a violent crime is only a few — no more than 10 cases, for sure,” said Tamaki Saito, a psychiatrist at the University of Tsukuba, about an hour northeast of Tokyo, who is a leading expert on hikikomori. “If we compare that with the general population, I think it’s fair to conclude that hikikomori noticeably have no relation to crimes. They are a group with a low crime rate.”

Although some studies suggest that hikikomori commit acts of domestic violence at higher rates than the general population, experts say the most pressing problem is that those with the condition, like others in Japan, rarely seek help for their mental health problems. Hikikomori may be affected by schizophrenia, depression or anxiety, or they may be on the autism spectrum.

“The scope of the problem is not things like a stabbing by a person who happens to be hikikomori,” said Alan Teo, an associate professor of psychiatry at Oregon Health and Science University in Portland who has researched social withdrawal in Japan. “But more the scope of the problem is in terms of hundreds of thousands of individuals who have been in this protracted state of withdrawal without active engagement in mental health care.”

Families are often ashamed to tell anyone that their child is struggling.

“Parents don’t disclose the state of their children to outside society,” said Tomiko Kushihashi, who runs a local chapter in Hyogo Prefecture, west of Kyoto, of Kazoku Hikikomori Japan, a support group for families of shut-ins. “The entire family is isolated from the society without calling for help.”

A looming crisis, experts say, is that a large cohort of hikikomori are getting older, with little indication that they will ever be able to reintegrate into society. Their parents, as they grow older, worry about who will look after these disconnected adults.