Hypocortisolism in attention deficit hyperactivity disorder – roles of sex, comorbidity, and symptom presentation

Abstract

Objective: Low activity of the hypothalamic-pituitary-adrenal axis (HPAA) has been found in children with ADHD. The condition may be related to the reduced attention regulation capacity and/or to comorbid oppositional defiant or conduct disorder (ODD/CD). Sex differences are probable but not sufficiently studied. We analyzed hypocortisolism and the reactivity of the sympathetic nervous system (SR) in boys and girls with ADHD and healthy controls. Methods: The sample comprised 205 children (98 with ADHD and 107 healthy controls). DSM-5 phenotypic symptom presentation and comorbid ODD/CD were assessed using clinical interviews. Hair cortisol concentration (HCC) was used to assess the long-term, cumulative activity of the HPAA. SR was assessed via skin conductance response (SCR). For control purposes, comorbid internalizing symptoms and indicators of adverse childhood experiences were assessed. Children were medication naive.Results: Boys presenting with predominantly inattentive symptoms (ADHD-I) showed lower HCC than did healthy boys. Girls presenting with combined symptoms (ADHD-C) showed higher HCC than did healthy girls (p’s<.05, sex-by-group interaction, F(2,194)=4.09, p=.018). Boys with ADHD plus ODD/CD showed a blunted SR (p<.001, sex-by-group interaction, F(2,172)=3.08, p=.048). Conclusion: HCC constitutes an easily assessable, reliable, and valid marker of phenotypic ADHD-related features. It indicates more homogenous subgroups of ADHD and might point to specifically involved pathophysiological processes.