The variables that in´uence mental disorders and problem behaviors likely contribute synergistically to outcomes (Cerda, Sagdeo, Johnson, & Galea, 2010; Nader, in press). Some of the youth-related factors associated with the expression of aggression and other problem behaviors also have been identižed in individuals who do not commit aggression such as targeted school shootings or hostage takings. As this implies, it is unlikely that emotional and behavioral disturbances can be explained by individual risk factors such as a single temperamental, behavioral, or environmental characteristic (Nader, 2008; Rutter, 2003).