Changes in Cortisol and in Oxidative/Nitrosative Stress Indicators after ADHD Treatment

ADHD, one of the most prevalent diseases during childhood, we still do not know its precisely origin, although oxidative/nitrosative stress and the hypothalamic-pituitary-adrenal axis are suggested contributors. Methylphenidate, among others, is the main drug used in these patients, but its effects on relevant markers and structures remain unclear. This study, involving 59 patients diagnosed with ADHD according to DSM-5 criteria, aimed to assess changes in cortisol levels (using cortisol awakening response, CAR) and oxidative/nitrosative status with the treatment. Blood samples before and 3 months after treatment with methylphenidate were used to measure oxidative and inflammatory markers, and the endogenous antioxidant activity, while saliva samples tracked cortisol awakening response (CAR). The results show a treatment-related improvement in the redox profile, with the reduction of advanced oxidation protein products (AOPP), lipid peroxidation (LPO), and nitrite plus nitrate (NOx) levels, and the increase of the enzymatic activities of glutathione reductase (GRd) and catalase (CAT). Moreover, the area under the curve (AUC) of CAR increased significantly, indicating increased reactivity of the HPA axis. These result support by the first time the involvement of the endogenous antioxidant system in the pathophysiology of ADHD.