Low hair cortisol concentration and emerging attention-deficit/hyperactivity symptoms in preschool age.

Previous research demonstrated hypoactivity of the HPA axis in children with attention-deficit/hyperactivity disorder (ADHD) or externalizing symptoms. We analyzed the predictive association between the long-term HPA axis activity and increasing symptoms of ADHD in the preschool period. The sample consisted of n = 125 4-year-old children and their families (including n = 64 children with elevated ADHD symptoms). ADHD symptoms were assessed by a structured clinical interview with the mother and by parent- and teacher-report questionnaires. The long-term HPA axis activity was assessed by the hair cortisol concentration (HCC) (over a 3-month period). After controlling for potential confounders, low HCC predicted an increase in ADHD symptoms between the age of 4 and 5 years. Exploration of gender effects revealed that cross-sectional and predictive associations were significant in boys but not in girls. Low HCC might thus be regarded as an early marker of a possibly gender-related developmental pathway to ADHD.

Hair cortisol concentration in preschoolers with attention-deficit/hyperactivity symptoms-Roles of gender and family adversity.

OBJECTIVE: Previous studies on the association between hypothalamic-pituitary-adrenal axis (HPAA) activity and ADHD yielded inconsistent findings, particularly in younger children. This might be due to the heterogeneity of the disorder, making moderator effects of variables probable, which circumscribe more homogenous subgroups. There have been indications of moderator effects on this association by gender of child and exposure to family adversity. Moreover, difficulties in capturing long-term basal HPAA activity in younger children might have contributed to the inconsistencies. We therefore analyzed moderator effects of gender and family adversity while using the hair cortisol concentration (HCC) to assess integrated long-term HPAA. METHODS: The community-based sample consisted of 122 4-5-year-old preschoolers (71 screened positive for elevated ADHD symptoms). ADHD symptoms were measured by a clinical parent interview and parent and teacher questionnaires. HCC in the most proximal 3-cm scalp hair segment was analyzed using luminescence immunoassay. An extended family adversity index was used. RESULTS: Hierarchical linear regression analyses yielded an interaction effect (p<.05) between ADHD symptom groups and gender on HCC, indicating a low HCC in boys with elevated ADHD symptoms. Further exploratory analyses revealed that this interaction effect was most pronounced under the condition of family adversity. The results held after controlling for oppositional, anxiety, and depressive symptoms. CONCLUSION: Low HCC might indicate a specific pathogenic mechanism in boys with elevated ADHD symptoms. This mechanism might further involve an exposure to family adversity. However, the results need to be cross-validated before definitive conclusions can be drawn.