Cortisol is the body's natural stress-fighting hormone, so when a person gets into a stressful situation, cortisol is one of the hormones produced. Ironically, the opposite of what you might think would happen regarding cortisol occurs. Low levels of cortisol, rather than high levels, lead to aggression. According to Science Daily, low cortisol levels leads to extremely aggressive behaviour in boys age 7 to 12.
Researchers from the University of Chicago report results from a four-year study of boys with behavioural problems. Boys with low cortisol levels began antisocial acts at a younger age than their peers, displayed three times the aggressiveness of other boys their age and were three times as likely to be singled out as a bully or mean.
Understanding the relationship between low cortisol levels and aggression may help psychiatrists treat delinquent adolescents, a problem that traditionally is difficult to treat, according to Science Daily. Children who have this type of conduct disorder tend to be this way for decades and account for much of the violence and crime in society.
The research by the University of Chicago also suggests that a biological or genetic disorder may be the reason for lowered cortisol levels. In this four-year study, researchers assessed boys who started fights, used weapons, were cruel to people and animals, stole and forced sexual acts. The findings showed a relationship to low cortisol levels and these behaviours. All the boys had similar socioeconomic backgrounds, IQs and ethnicities.
Society may also play a role in aggressive behaviours and subsequently, low cortisol levels. Physical abuse, for example, may put the body in extreme stress, especially if this happens to a child, according to an article by Stephanie van Goozen on the neurobiology of childhood antisocial behaviour in Do You Mind, a blog about the brain and behaviours. Van Goozen's theory is that different types of stressors can result in different types of stress response systems in later life, meaning that exposure to early abuse may cause a bodily reaction, which would affect how much cortisol would be delivered in future stressful situations.
Researchers speculate as to why lower cortisol levels lead to increased aggression. Boys who have the lower cortisol levels may be less afraid of punishment, according to Keith McBurnett, Ph.D. and assistant professor of psychiatry at the University of Chicago. Children who are not afraid of punishment may not feel stress at the threat of punishment and, therefore, do not avoid stressful or negative behaviours.