Aggression, violence, and cruelty are symptoms of psychiatric illness. They reflect abnormalities in the regulation of the stress and emotion circuitries. The functioning of these circuitries depends upon the interaction between genetics and environment. Abuse and neglect during infancy, as well as maternal stress and poor quality of maternal care, are some of the causes that produce these types of abnormal behavior. Research on the neurobiological bases of emotion regulation will allow the detection of the population at risk.