Meanwhile, the anticonvulsive drug Dilantin® has been used successfully to cut the number and intensity of aggressive acts committed by impulsive convicts, reports Ernest S. Barratt, Ph.D., a professor of psychiatry and behavioral sciences at the University of Texas Medical Branch in Galveston. The drug, however, has had little effect on those who committed premeditated aggression, he says.
While serotonin system deficiency seems to be one of the main triggers for aggressive behavior, there are other culprits. Coccaro has found a link between a life history of aggression and elevated levels of another neurotransmitter, vasopressin, in the cerebrospinal fluid. Higher levels of hormones like testosterone may also play a part in increasing aggressive tendencies, some researchers believe, but Coccaro says he has not found a definite connection.
With the new understanding of the role of neurotransmitters, scientists may one day be able to repair genetic flaws that interfere with their function, but not in the near future. "We know very little about the identity and function of specific genes that contribute to the risk for violent behavior, so it's pretty foggy," says Evan S. Deneris, Ph.D., associate professor of neuroscience at Case Western Reserve University School of Medicine.
Many researchers have concluded that environment can lead to violent behavior. In general, children who are severely punished or witness aggression are more likely to be aggressive later in life, Coccaro says. On the other hand, mistreated children with high levels of enzymes that help keep aggression in check "were less likely to develop antisocial problems," according to Avshalom Caspi, Ph.D., a University of Wisconsin psychology professor who has studied the connection between genes, the environment and aggression.