Spotting Bad Seeds

A few youngsters start a career of antisocial behavior early in life--destroying property, being cruel to animals, or getting booted out of grade school for fighting. At least some troublemakers, it seems, have a flawed biological response to stress that may help set them on the wrong path: A new study has found low levels of the stress hormone cortisol in persistently aggressive boys.

Scientists have found several clues that there are biological aspects to entrenched antisocial behavior. For example, psychologist Adrian Raine of the University of Southern California in Los Angeles has found that boys with low levels of physiological arousal as teenagers--as indicated by both heart rate and brainwaves--are more likely to commit a felony later in life.

The latest evidence comes from the University of Chicago, where psychologist Keith McBurnett and colleagues followed 38 boys aged 7 to 12 diagnosed with conduct disorder, a cluster of behaviors such as stealing, fighting, and sexual aggressiveness. Earlier work had hinted at a link between antisocial behavior and low levels of cortisol, a hormone that rises with stress levels. Probing this further, McBurnett's group tested the boys' saliva twice over a 4-year period and rated social behavior from interviews with parents, teachers, and classmates. The really bad actors and those who started misbehaving earliest, it turned out, also had the lowest cortisol levels, the team reports in this month's Archives of General Psychiatry.

Raine says the findings fit with research showing that people with aggressive antisocial personalities often have sluggish nervous systems. Why the link? Researchers say it means they need to go to extremes to achieve stimulation, and also that they don't experience normal feelings of inhibition and fear of giving in to destructive impulses.

Measuring cortisol levels, McBurnett says, might help identify which troublemakers are just going through a phase and which have a persistent aggressive streak. The task now, he adds, is to sort out to what extent a dampened response to stress is ruled by genes and to what extent by early emotional trauma, which can permanently alter the hormonal system that generates cortisol.