Plasma cortisol and aggression in boys with ADHD

Objective: The results of several studies suggest an inverse relationship between cortisol secretion and aggressive behavior. This study examined basal plasma cortisol levels in aggressive and nonaggressive boys with attention-deficit hyperactivity disorder (ADHD). Method: The subjects were 23 aggressive and 27 nonaggressive boys with ADHD, aged 7 to 11 years. After 3 days of a low monoamine diet and an overnight fast, an indwelling catheter was inserted into a forearm vein. Samples for plasma cortisol levels were obtained 105 and 115 minutes after insertion of the catheter. Results: A one-way analysis of covariance (ANCOVA) controlling for body mass revealed no significant difference in plasma cortisol between the aggressive and nonaggressive boys. Furthermore, when the children were alternatively divided on the basis of the presence or absence of a DSM-III-R diagnosis of conduct disorder, a one-way ANCOVA again revealed no significant difference in cortisol levels. Conclusions: The hypothesized inverse relationship between cortisol secretion and aggressive behavior in boys with ADHD was not found. These findings are consistent with a large body of literature indicating that the biological substrate of aggression is complex and that the identification of biological laboratory markers of aggressive behavior is not a clinically useful strategy at this time.