Public Release: 

Latest research on possible causes of violent behavior explored in C&EN article

American Chemical Society

Flawed brain chemistry, brain damage, genetic defects, an unhealthy psychological environment — take them individually or mix them together and you may have the right ingredients for violent behavior, reports a variety of researchers.

With 1.4 million violent crimes committed in the United States in 2000 — according to the Bureau of Justice Statistics — chemists, medical professionals, sociologists and other professionals are intensively studying the causes of aberrant behavior to find some therapies, says Chemical & Engineering News. C&EN, the weekly newsmagazine published by the American Chemical Society, the world's largest scientific society, takes an in-depth look at major research in this area in its June 2 issue.

For decades researchers have known that violent behavior is linked to the brain's serotonin neurotransmitter system, says Emil F. Coccaro, M.D., director of the Clinical Neuroscience and Psychopharmacology Research Unit at the University of Chicago. A neurotransmitter is a chemical that helps transmit nerve impulses through the nervous system. Serotinin is neurotransmitter in the brain that acts as a kind of brake on impulsiveness.

People with normal or above average levels of serotonin show more restraint and think things out, explains J. Dee Higley, Ph.D., a research scientist at the National Institute on Alcohol Abuse and Alcoholism. Those with low levels, on the other hand, "act first and think later and that gets them into trouble," Higley adds. "The problem is if you're impulsive and you have a short fuse and you get into a setting that's likely to elicit violence, you are going to be more prone to exhibit aggressive behavior."

In one study, Coccaro tried to increase serotonin levels by decreasing its re-absorption by neurons (the basic units of the nervous system) using the drug Prozac®. This therapy helped those who were moderately aggressive. The researcher plans to compare Prozac® to Depakote®, which also increases serotonin levels, in treating this group.

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.

Other factors researchers blame for inciting aggressive behavior include poor nutrition (interferes with neurotransmitters), elevated levels of such metals as lead in the body (lowers serotonin levels), brain damage due to injury or alcohol abuse, and viewing violence on TV, according to C&EN.

Despite all of the negative side effects of impulsiveness or aggressiveness, however, sometimes this kind of behavior is useful. It may be that impulsive, daring soldier who helps to take a hill during battle. Many explorers and settlers have had to be impulsive to take the chances needed to succeed, says Higley.

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To access the C&EN story on violence go to: http://pubs.acs.org/cen/science/8122/8122sci1page1.htm

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