Aggression may be defined as any form of behaviour directed toward the goal of harming or injuring another living being [2]. Aggression is a heterogeneous concept, which researchers have been trying to subdivide in various ways. The most evolutionary valid and biologically relevant distinction separates instrumental (predatory) and impulsive (reactive) forms of aggression. Each of these subtypes may be mediated by unique underlying neurocognitive systems [3] [4] [5]. Impulsive aggression is generally associated with high arousal, impulsivity, high affect and uncontrolled behaviour. In contrast, instrumental aggression refers to goal-directed, planned behaviour associated with low arousal and affect. While impulsive aggression is frequent in ADHD, instrumental aggression is more strongly associated with Conduct Disorder (CD).