Researchers at the University of Cambridge have discovered a link between reduced levels of the 'stress hormone' cortisol and antisocial behaviour in male adolescents.
Levels of cortisol in the body usually increase when people undergo a stressful experience, such as public speaking, sitting an exam, or having surgery.
It enhances memory formation and is thought to make people behave more cautiously and to help them regulate their emotions, particularly their temper and violent impulses.
The new research, funded by the Wellcome Trust, shows that adolescents with severe antisocial behaviour do not exhibit the same increase in cortisol levels when under stress as those without antisocial behaviour.
The findings suggest that antisocial behaviour, at least in some cases, may be seen as a form of mental illness that is linked to physiological symptoms (involving a chemical imbalance of cortisol in the brain and body).
The scientists, led by Dr Graeme Fairchild and Professor Ian Goodyer, recruited participants for the study from schools, pupil referral units, and the Youth Offending Service.
amples 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.
The differences between participants with severe antisocial behaviour and those without were most marked under stressful conditions. While the average adolescents showed large increases in the amount of cortisol during the frustrating situation, cortisol levels actually went down in those with severe antisocial behaviour.
These results suggest that antisocial behaviour 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.
Dr Fairchild said, "If we can figure out precisely what underlies the inability to show a normal stress response, we may be able to design new treatments for severe behaviour problems. We may also be able create targeted interventions for those at higher risk.
"A possible treatment for this disorder offers the chance to improve the lives of both the adolescents who are afflicted and the communities in which they live."