People belonging to some gangs in their life suffer from severe mental illness, a new study from Britain has found.

An estimated 5 percent of all people in the U.S. have been part of a gang at some point in their lives. Young people with gang affiliations are more likely to commit homicides and also use illegal drugs, according to Centers for Disease Control and Prevention. In the present study, researchers found that young men in gangs suffer from extreme levels of psychosis and mental disorders, driving up the cost of mental healthcare.

Researchers said that urban areas in Britain have higher number of gang members than other areas. This is also true for gangs in the U.S. CDC estimates say that gang membership in the last decade reached 14 to 30 percent in the urban areas.

The study was based on data obtained from 4,664 men aged 18 to 34 in Britain. Researchers found that 108 people in the study group were gang members and that 85 percent of them had a personality disorder. Also, about 25 percent of these gang members had psychosis.

More than half of the gang members surveyed had alcohol related problem; around a third of them had attempted suicide. Many people in the study group suffered from anxiety and fear of being victimized.

"No research has previously investigated whether gang violence is related to psychiatric illness, other than substance misuse, or if it places a burden on mental health services,"  Professor Jeremy Coid, Director of the Forensic Psychiatry Research Unit at Queen Mary, and lead author of the paper said in a news release.

 "Here we have shown unprecedented levels among this group, identifying a complex public health problem at the intersection of violence, substance misuse, and mental health problems among young men," the professor added.

The research is published in the American Journal of Psychiatry.