Abstract
BACKGROUND: Iron is a co-factor of tyrosine hydroxylase which is a critical enzyme in dopamine synthesis. Dopamine has been implicated in the pathophysiology of attention deficit hyperactivity disorder (ADHD). Our objective was to investigate the association of ferritin level with parent and teacher ratings and cognitive measures after controlling for age, sex, ADHD subtype, comorbid conditions, hemoglobin, mean corpuscular volume and reticulocyte distribution width in a large sample. METHODS: The study included 713 children and adolescents with ADHD (613 boys; age 7-15 years). Conners' Parent Rating Scale (CPRS) and Conners' Teacher Rating Scale (CTRS) were obtained. In a subgroup of patients we conducted Digit Span, Digit Symbol, Trail-making Tests as measures of attention and executive functioning. RESULTS: Multiple regression analysis indicated that CPRS Hyperactivity score was significantly associated with ferritin level (B =-0.12; t =-3.1; P < 0.01). Other CPRS and CTRS scores as well as cognitive measures were not associated with ferritin level. CONCLUSIONS: Although it is not possible to make an inference on causality in cross-sectional studies, the results of this largest-scale cross-sectional field study to date suggest that lower ferritin level might be associated with parent-reported hyperactivity after controlling for important confounding factors.