Theories to explain addictive behaviors in general may directly relate to the specific proclivity to exhibit excessive aggression in this subset of users. Certain personality traits and cognitive deficits coexist in individuals prone to both drug abuse and violence, suggesting a common origin. Because these excessive and compulsive behaviors have been linked with aberrations in the metabolism and activity of the neurotransmitters, dopamine and serotonin, their origins may be partly genetic or biological. Alterations in neurotransmitter function influence activities within the brain's reward center to perturb nervous system arousal levels, thereby increasing stimulation-seeking behaviors. Manifestations of neurobiological aberrations can be measured in physiological and biochemical processes that serve to mediate behavioral and psychological outcomes. The author concludes drug abuse and violence may originate from overlapping processes, notably dopamine and serotonin metabolic mechanisms that modulate reward systems responsible for states of arousal. 169 references, 4 notes, and 3 figures