some people have it and never become floridly psychotic. A lot of times stress triggers it. Schiz/s have very low thresholds for stress. It used to be noticed earlier in men b/c they were the ones to go to college and go to work , where women often became housewives and stayed at home. given a relatively calm life, a lot of sciz do not end up walking the streets naked. But now, women go to work as often as men, and its about equal.College is prime time for it to show up.. Away from home and on their on, stresses increase , along with increased social interaction. That is often when it is first noticed , at college age. There is certainly a heridity factor. There is not enough research into this and other mental illnesses. So many people are afflicted, it is hard to understand why they do not research it more. It is a difficult to treat illness, and at the best, the person usually ends up very low functioning, perhaps in a cleaning job, or on disability, or working nights.There are always exceptions, ie the movie the beautiful mind.
Some people get to the point they know they are hearing voices, but find comfort in them, so are reluctant to give them up .Drugs and alcohol certainly do increase the voices. In some people they may trigger their first eposide.
Contray to the movies, these people are usually not dangerous to others, but more inclined to hurt themselves
It is a terribly sad illnesss that takes away a life.. I'm glad i no longer work in this area, as it is hard to see the hopelessness of those afflicted.