Why are some men more aggressive than others?

NEW YORK, June 29 (Reuters) Why are some men confrontational or break objects in fits of anger, while others appear to be more in control under similar circumstances? New study findings suggest the answer may involve genetic differences in combination with the men's early environment.

A variation in a gene involved in the activity of the brain chemical serotonin, which is known to play an important role in regulating emotions and impulses, may cause some men to have problems controlling their anger. Yet, this appears to be true only for men raised in certain environments, in particular under adverse circumstances.

''The take-home message is not to change the genes or the brain, but the environment in which the brain matures or develops,'' study author Dr. Stephen B. Manuck, of the University of Pittsburgh, told Reuters Health.

Studies have shown that some people with psychiatric disorders and those imprisoned for an impulse-related crime are either deficient in serotonin or exhibit poor regulation of the brain chemical.

In previous studies, researchers also found that men carrying one form of the monoamine oxidase-A (MAOA) gene responsible for inactivating serotonin were more likely to be violent and antisocial than men with a different form of the gene. However, the negative behavior was seen only among men who were abused in childhood.

Manuck investigated if this was also the case among men who exhibited less dramatic aggression. He studied 531 healthy, white men from the general population and found that the same form of the MAOA gene found in violent criminals was also more common in study subjects who reported a history of confrontational and antagonistic behavior, such as fighting, having temper tantrums or breaking objects in fits of anger.

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