Low levels of the stress hormone cortisol have been linked to antisocial behaviour in adolescent boys

Cortisol levels in the body usually surge in stressful situations, thought to help people regulate emotions. But a Cambridge university study found this did not happen in boys with a history of severe antisocial behavior. The Biological Psychiatry study suggests some bad behavior may be a form of mental illness linked to a chemical imbalance in the brain. An increase in cortisol levels is thought to make people behave more cautiously, and help them to regulate their emotions, particularly their temper and violent impulses. The Cambridge team recruited participants for the study from schools, pupil referral units and the Youth Offending Service. Samples of saliva were collected over several days from the subjects in a non-stressful environment to measure levels of the hormone under resting conditions. The young men then took part in a stressful experiment that was designed to induce frustration. Samples of saliva were taken immediately before, during and after the experiment to track how cortisol changed during stress. While the average adolescents showed large increases in the amount of cortisol during the frustrating situation, cortisol levels actually went down in those with histories of severe antisocial behaviour. The researchers said the results suggest that antisocial behavior may be more biologically-based than previously considered, just as some individuals are more vulnerable to depression or anxiety due to their biological make-up.