Objectives: There is growing interest in the role of the hypothalamic-pituitary-adrenal (HPA) axis in neuropsychiatric disorders and there is some evidence that the HPA axis may be underfunctional in behaviorally disturbed children. However, co-morbidity is common in childhood neuropsychiatric disorders. Stimulant medication is widely used in the treatment of Attention-deficit hyperactivity disorder (ADHD) and can increase cortisol secretion when given acutely. We therefore set out to determine the whether salivary cortisol would be reduced in a group of children with ADHD/ODD (Oppositional-defiant disorder) and to examine the effect of stimulant medication on any such relationship.
Design: Salivary cortisol was determined in thirty-two children with co-morbid ADHD and Oppositional-defiant disorder (ODD) according to DSM-IV criteria, compared to twenty-five healthy controls of similar age and ethnic background. Data were analysed according to prescription of stimulant medication in the patient group.
Results: Salivary cortisol was significantly lower in the ADHD/ODD group than in the controls. Further analysis revealed that this reduction was restricted to the subgroup of patients not prescribed stimulant medication.
Conclusions: The results support the possibility of a dysfunction of control of the HPA axis in these behaviorally disturbed children. A reduction in salivary cortisol could reflect underarousal, an elevated threshold for detection of stressors or a subsensitivity of the HPA axis itself. It remains to be determined whether the ability of stimulant medications to negate the apparent deficit in cortisol secretion in these ADHD/ODD patients is an unrelated consequence of increased dopamine release or a reflection of their therapeutic benefit. The use of stimulant medication for co-existing ADHD should be taken into account in future studies of cortisol in behaviorally disturbed children.