Change in Blood Cortisol Levels During 6-Month Methylphenidate Treatment in Children with ADHD

Background: We sought to investigate the changes in hypothalamic-pituitary-adrenal (HPA) axis after methylphenidate (MPH) treatment, and their association with attention deficit hyperactivity disorder (ADHD) symptomatology. Methods: We included 86 children with ADHD and 58 healthy controls in this study. Morning cortisol was measured at baseline, 1st, 3rd, 6th month of MPH treatment. K-SADS-PL and Conners' Parent/Teacher Rating Scales (CTRS and CPRS) were collected at each visit. Results: There was an increase with borderline significance (p=0.054) in cortisol levels measured before and after the 6th month of MPH treatment. However, there was no significant change in control group (p > 0.05). In gender subgroups there was a significant change in boys (p = 0.008), whereas no similar increase was found in girls (p > 0.05).While there was a significant increase in cortisol levels of ADHD combined (ADHD-C) type, no significant change was found in ADHD inattentive (ADHD-I) type. Boys had higher rates of improvement in most of the subscales. While there was a significant decrease in all subscale scores of CTRS and CPRS in ADHD-C group, there was no significant difference in most subscales in ADHD-I group. Conclusions: Change in plasma cortisol levels may be useful in predicting the long-term treatment response, especially in the male gender and ADHD-C subgroup.