Has anyone investigated how much being a victim of gangstalking has to do with depression, suicide, etc?

Have any doctors investigated whether being a victim of mobbing and gangstalking is having an effect on people and causing depression, suicide, etc and that maybe those people who do all the killing at schools and shopping malls, even at the McDonald's in San Ysidro were bullied and also the postal workers were bullied and picked on and were victims of mobbing and gangstalking and why do the cops and firemen insist on doing this mobbing and gangstalking when they should know what it could lead to, so why do they single certain people out and pick on them?