Researchers from France also say children with ADHD and iron deficiencies exhibit more severe symptoms.
"Our findings could have a major and immediate impact on the treatment of children with ADHD," the researchers write in the December issue of the Archives of Pediatric and Adolescent Medicine.
Iron Stores Predict Symptom Severity
Past research has linked iron deficiency in infancy to slower brain development and poorer school performance later in childhood. Animal studies have linked iron deficiency to abnormal muscle movement or restlessness. Iron deficiency is also common in people with the movement disorder known as restless legs syndrome.
Lead researcher Eric Konofal, MD, PhD, tells WebMD that these earlier findings led him to question whether iron deficiency plays a role in ADHD, a disorder characterized by inattentiveness, hyperactivity, and impulsivity.
In an effort to answer the question, Konofal and colleagues measured blood levels of the protein ferritin in 53 children with ADHD and 27 children without ADHD but who had a mild reading disability. Ferritin allows the body to store iron and is used as a measure of iron levels.
Eighty-four percent of children with ADHD appeared to have abnormally low ferritin levels, compared with 18% of children without ADHD.
The children with the most severe iron deficiencies were also the most inattentive, impulsive, and hyperactive. This led the researchers to conclude that "low iron stores may explain as much as 30% of ADHD severity."
The researchers say the reason for the low iron levels in children with ADHD is unclear. The children in the study did not have evidence of malnutrition, which might contribute to low iron levels.
Too Soon to Supplement?
Low iron levels in the brain are known to alter the activity of dopamine, a chemical involved in controlling movement. The researchers suggest that this could explain the observed link between iron stores and ADHD.
Konofal says he hopes to collaborate with ADHD researchers in the United States on a much larger study to confirm the findings.
While he and colleagues write that their study could have an immediate impact on the treatment of ADHD, Konofal tells WebMD that it is probably too soon to recommend iron supplementation for all children with the disorder. He added, however, that kids with ADHD should be tested for iron deficiency.
Pediatrician and ADHD expert William Coleman, MD, tells WebMD that it is clear that malnourishment can lead to an attention-deficit-like syndrome often misidentified as ADHD. While he calls the latest findings intriguing, he says he doubts that iron deficiency will turn out to be a major cause of ADHD.
"If it is involved, I believe iron deficiency is responsible for only a very small segment of the problems associated with ADHD," says Coleman, professor or pediatrics at the University of North Carolina Medical Center.