Early evidence in human subjects suggests that symptoms of attention deficit hyperactivity disorder (ADHD) may be caused by CNS dopamine dysfunction. Iron, which functions as a coenzyme in dopamine synthesis, has, in animal models, been determined to be necessary to maximize dopamine receptors and function. Investigators therefore hypothesized that iron deficiency might correlate with symptoms of ADHD and designed a trial to test that association.
Fifty-three children with ADHD, between 4 and 14 years old (45 boys, eight girls), and 27 controls, all from the same school district in Paris, were studied. The children with ADHD and controls were medication-free for at least two months. Using the Conners Parent Rating Scale, investigators evaluated the severity of symptoms and then measured the serum ferritin level, as well as blood hemoglobin, hematocrit, and iron levels.
In children with ADHD, the serum ferritin level was, on average, half as high as in children without ADHD. In the ADHD group, 84% of subjects had an "abnormally low" serum ferritin level, compared to 18% of controls. In addition, the ferritin level was "extremely low" in 32% of children with ADHD (indicating low iron stores), compared to 4% of controls. Most significantly, the serum ferritin level correlated inversely with the severity of ADHD: Children with the most severe iron deficiency were the most inattentive, impulsive, and hyperactive. Levels of serum iron, hemoglobin, and hematocrit did not differ between the two groups and were within normal ranges (Konofal E et al: Arch Pediatr Adolesc Med 2004;158:1113).