Testosterone, it seems, has gotten a bad rap. The hormone has been blamed for so many barroom fights and blackened eyes that, some researchers say, it's time to clear its name. The true culprit associated with all these violent acts, they say, could be another hormone called cortisol.
In a study, published in Thursday's Archives of General Psychiatry, University of Chicago assistant professor Keith McBurnett, Ph. D., and his colleagues have found that young boys who were persistently aggressive had lower levels of cortisol in their saliva. (Cortisol is a hormone released by the adrenal gland in response to stress. Normally, when an emergency is confronted, cortisol levels go up; when the situation goes away, the levels go down.)
"Bullying other kids, physically fighting and threatening others is
strongly linked to low cortisol," says McBurnett, the lead author of the study. "Cortisol is giving us a clue that there might be some biological differences with these kids who are really at chronic risk for aggression."
For four years, McBurnett and his colleagues followed 38 boys ages 7 to 12 who were referred to a clinic for behavioral problems. The boys with lower levels of cortisol were more likely to be more aggressive -- starting fights, hurting animals, brandishing weapons -- than those with more of the hormone. They were also the ones pointed out by other students as the "meanest" in class.
"If we get a kid who shows aggression and they continue to show aggression, that's a fairly good predictor that they will engage in antisocial behavior," McBurnett says. Indeed, there is some evidence of this. The impetus for McBurnett's study was to follow up on earlier research with prisoners showing the most violent offenders had lower levels of cortisol in their saliva. (Cortisol is also found in blood, but for research purposes, it's easier to take saliva samples.)
While no one knows how cortisol relates to aggression, researchers
hypothesize that lower levels of it might reflect indifference to the consequences of one's actions. But McBurnett is quick to point out that he believes the gun-toting teens responsible for the wave of violence in schools across the country is a different type of aggression. He says their violence is more of a one-shot deal than that displayed by the kids he has been studying -- boys who are
consistently getting in trouble for their behavior.
But Debra Niehoff, author of "The Biology of Violence," is not so sure. She thinks that there may be a connection between these seemingly random violent acts and how their bodies were responding to stress. When man was living on the plain, she says, it was very clear how the body reacted when in an emergency. But times have changed.
"The challenges we face today aren't life-threatening emergencies like they were before. They're the stress of living in a violent home, the stress of living in a dysfunctional community, the stress of going to school and being an outcast because you're a nerd," Niehoff says. "That kind of stress the human body was not set up to handle."
So will we see researchers scouring the classrooms in elementary schools, collecting saliva samples in hopes to identify the potential future murderer? No, says McBurnett. But if we can identify the more violent kid in the class before he draws blood, he adds, society can then perhaps redirect him into other fields that might tap into his sense of excitement or danger.