Low stores of iron may put children at increased risk for attention deficit hyperactivity disorder (ADHD), according to a new study.
Eric Konofal and colleagues evaluated 53 children and young adolescents with ADHD, as well as 27 non-ADHD children with mild learning disabilities who served as controls. All of the children were medication-free for at least two months prior to entering the study. The researchers measured the children's serum ferritin levels to determine their iron status, and used the Conners' Parent Rating Scale to measure how severe the symptoms of each ADHD subject were.
Konofal et al. report that serum ferritin levels were significantly lower in the ADHD group than in the controls. Overall, they say, "serum ferritin levels were abnormal in 84 percent of children with ADHD and 18 percent of controls." One-third of the ADHD children had iron levels in the extremely low range, compared to only 3 percent of the controls. Moreover, serum ferritin levels were inversely correlated with the severity of ADHD symptoms. The researchers say their data indicate that low iron stores may explain as much as 30 percent of ADHD severity.
Konofal and colleagues speculate that iron deficiency leads to inattentive and distractible behavior and to learning disabilities, "a finding consistent with the role of iron deficiency in cognitive deficits and mental retardation."
"Because hemoglobin and hematocrit levels were normal," Konofal et al. say, "the low ferritin levels should be considered a specific and primary abnormality." They conclude that "if serum ferritin levels should prove to be decreased in cerebrospinal fluid as well, this would suggest that a brain iron deficiency may underlie the symptoms of ADHD."
Iron is a coenzyme needed for the synthesis of neurotransmitter dopamine, and iron deficiency alters the density and activity of dopamine receptors in animals. Abnormal dopamine function, in turn, is strongly linked to ADHD. Thus, the researchers hypothesize, low ferritin levels may contribute to ADHD by altering brain dopaminergic activity.
The researchers conclude that pediatricians should consider iron supplementation as a first-line treatment for children with both iron deficiency and ADHD symptoms. They note that children or adults with "restless leg syndrome" may be especially likely to have pathologically low iron stores, as iron deficiency is a known cause of this syndrome.
"Iron deficiency in children with attention-deficit/hyperactivity disorder," Eric Konofal, Michel Lecendreux, Isabelle Arnulf, and Marie-Christine Mouren, Archives of Pediatric and Adolescent Medicine, Vol. 158, December 2004, 1113-15. Address: Eric Konofal, Service de Psychopathologie de l'Enfant et de l'Adolescent, Hôpital Robert Debré, 48 Boulevard Serurier, 75020 Paris, France, firstname.lastname@example.org- paris.fr.