Biochemical Factors in Predicting Violence

Dopamine

The dopamine system has been implicated in displays of aggressive or violent behavior. When the dopamine system is activated, novelty seeking and self-stimulation behaviors increase. When this system goes awry, however, behavior may be activated in the absence of a reward, a threat, or some other appropriate stimulus. This “approach system” can produce dangerous asocial and disruptive behavior when it is activated in the absence of an appropriate social setting or provocation. The overproduction of dopamine has been associated with psychotic behavior, and has been linked to antisocial behavior and violence. Antipsychotic drugs that decrease dopamine levels tend to decrease fighting behaviors.

Serotonin

An abnormally low level of serotonergic activity is another significant player in influencing impulsive-aggressive behavior. Lesions that switch off areas of the brain that are dense with serotonin connections produce rage and attack behaviors. Scores of studies have found several indicators of lowered serotonin activity in studies of juveniles and adults characterized as violent or impulsive, in contrast to those who are not. Further refinements to these investigations, however, show that serotonin is more specifically responsible for regulating impulse control than aggressive behavior. The implications are that when serotonin activity levels are relatively low, the tendency or predisposition to behave in certain ways (e.g., violently) that may be related to certain personality traits (e.g., a negative or hostile mood) is less likely to be inhibited.

Norepinephrine (Noradrenaline)

Norepinephrine (NE) is of particular interest due to its involvement in stress responses, emotions, attention, and arousal. It plays a primary role in the so-called fight-or-flight response by causing the release of stress hormones from the adrenal glands, and exciting the central and peripheral nervous systems. NE activates the fight-or-flight response by stimulating various brain structures, from the frontal cortex, to the limbic system (controlling emotions and survival functions), to the brainstem.

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