Members appear to be predisposed to mental illness:
The researchers aren’t certain why a third of these British gang members have tried to kill themselves, but believe suicidal behavior could be linked to other psychiatric illnesses or impulsive acts of violence directed inwards. Gang members are also quite young, [Professor Jeremy] Coid said. “The average age for gang membership is 15,” a demographic which wasn’t included in the study of 18 to 34 year olds. So do gang members become mentally ill as a result membership? Often extorted and pressured to express unfaltering loyalty, the study can’t say much about the psychiatric foundations of matriculating gang members.
The Dish 