The study regarding car crashes also looked into the correlation between whether or not car crashes only killed the driver or other people too, and found a clear correlation in additional deaths:

Murder-suicides leads to more "accidents" with head-on crashes etc., while "clean" suicides with nobody else involved tends to lead to an increase in "accidents" that don't risk other peoples life.

"Influence" is a fantastic book. Though it's downright chilling in how it tears apart the illusion of how much control we have of how we act.