According to The Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), attention deficit-hyperactivity disorder (ADHD) afflicts 3% to 7% of children, although percentages may be higher in certain populations. Treatment with dopamine stimulants is often helpful; scientists believe that might be because ADHD is related to problems involving dopamine pathways in the brain. And because iron is needed for dopamine synthesis, it's possible that ADHD symptoms are related to iron deficiency. To explore this possibility, French researchers conducted a study comparing levels of ferritin, the protein complex to which iron binds, in children with and without ADHD.

Of 110 children referred to a Paris hospital for "school-related problems," 53 received a diagnosis of ADHD, according to the criteria listed in the DSM-IV and results of a structured clinical interview. These 53 children were compared with 27 age- and sex-matched controls with mild reading disabilities but no neuropsychiatric or medical problems, who were referred from the same school system.

FIGURE. A stereoscopic, three-dimensional computer model of a complex ferritin, a protein used for iron storage. A recent study found that in children with ADHD the mean serum ferritin level was half that in the children in a control group.

Although the children with ADHD weren't anemic-their hematocrit and hemoglobin values were normal-they were deficient in iron stores: the mean serum ferritin level in the children with ADHD was half that in the control group (23 ng/mL, versus 44 ng/mL). The severity of ADHD symptoms increased as ferritin levels decreased. According to the Conners Parent Rating Scale (CPRS), which measures ADHD symptoms, including hyperactivity, cognitive functioning, and oppositional behavior, the levels of cognitive functioning in the children with ADHD were significantly lower than those in the control group. Also, children in the ADHD group were less attentive and more distractible than those in the control group.

Because the only subscale in the CPRS to reach statistical significance was the cognitive sub-scale, it's difficult to assess whether this study was measuring ADHD itself or those cognitive problems that may be related to it, especially since the study subjects were recruited from a pool of children referred for school problems. More studies of iron deficiency in children with ADHD and in children with specific cognitive deficits will be needed to answer this question.-Fran Mennick, BSN, RN

Konofal E, et al. Arch Pediatr Adolesc Med 2004;158(12):1113-5.