Assoziation der Cortisolkonzentration im Haar mit der Entwicklung von Symptomen der Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS) im Vorschulalter

Background: Previous research on the association between hypothalamic-pituitary-adrenal (HPA) axis activity and ADHD/externalizing symptoms yielded inconsistent results particularly in preschool years. Some studies observed lower basal cortisol levels in children with ADHD. It has been suggested that a low concentration of basal cortisol is a biomarker of ADHD. ADHD becomes increasingly prevalent in preschool age and it has been assumed that low basal cortisol level may precede the manifestation of ADHD. The hair cortisol concentration (HCC) which has been shown to validly reflect HPA axis activity, however, has not yet been used in this context. We hypothesized that the children’s HCC at the age of four years predicts an increase in ADHD symptoms across a twelve months period between the age of four and five years. Further hypotheses pertained to the prediction of the development of the inattentive symptoms as well as symptoms of hyperactivity-impulsivity by low HCC. Stability of HCC across the twelve months period was analysed. Methods: The sample consisted of n=125 four-year-old children and their families (including n=64 children with elevated ADHD symptoms). Children were seen twice, i.e. at the age of four years and twelve months later, at the age of five years. ADHD symptoms were assessed by a structured clinical interview with the mother and by parent and teacher-report questionnaires. For determination of long-term cortisol exposure, three centimetre of hair (indicating the concentration across a three months period) were used. Comorbid oppositional symptoms were assessed by questionnaires. The research for this thesis was funded by a grant from the German Research Foundation (DFG, Be2573/3-1,2) to Prof. Dr. Katja Becker and Prof. Dr. Ursula Pauli-Pott. Results: The HCC was stable between four and five years. After controlling for maternal education level, gender of the child, ADHD symptoms at the age of four, comorbid oppositional symptoms and hair washing frequency, low HCC predicted an increase in ADHD symptoms across twelve months between the age of four and five years. HCC did not predict the development of inattentive symptoms between the age of four and five years but significantly predicted an increase in the hyperactive-impulsive symptoms. Conclusions: Low HCC might indicate a neurobiological deviation before the phenotypic complex behavioral ADHD symptoms increasingly emerge. A low HCC might be regarded as a biomarker and an early predictor of ADHD-symptom development.