Researchers at OHSU Doernbecher Children’s Hospital have defined for the first time a causal link between blood lead exposure and attention deficit hyperactivity disorder in humans. While previous studies have associated lead blood levels with ADHD, research published in Psychological Science is the first to confirm previous hypotheses that exposure to lead in miniscule amounts typical in the U.S., or less than 10 parts per billion, increases symptoms in some individuals with ADHD. The paper “Variation in iron metabolism gene moderates the association between low-level blood lead exposure and Attention-Deficit/Hyperactivity Disorder” is a collaboration among researchers at OHSU Doernbecher Children’s Hospital, Michigan State University and the University of Iowa.
Joel Nigg, Ph.D., principal investigator; director, OHSU ADHD & Attention Research Program; director, Division of Psychology, OHSU Doernbecher Children’s Hospital; and professor of psychiatry and behavioral neuroscience, OHSU School of Medicine, said the findings bridge genetic and environmental factors, helping illustrate one possible route to ADHD. The research also demonstrates that conditions like ADHD can be prevented.
To conduct this research, Nigg and colleagues evaluated lead blood level in 386 healthy children aged 6 to 17. Half of the children had been carefully diagnosed with ADHD. All children were within the safe lead exposure range as defined by the Centers for Disease Control and Prevention, and the blood lead level in the sample was typical of the national U.S. population of children. The study also found that lead effects were more robust in males, which is consistent with previous research specific to neurodevelopmental conditions and gender. Children without HFE C282Y mutations showed amplified symptoms as lead exposure increased, but not as consistently.
The scientists do not purport that lead is the only cause of ADHD symptoms, nor does the research indicate that lead exposure will guarantee an ADHD diagnosis; rather, the study demonstrates that environmental pollutants, such as lead, do play a role in the explanation of ADHD. Despite U.S. government regulations that drastically reduced environmental exposure to lead, the neurotoxin is still found in common objects such as children’s toys and costume jewelry. It also continues to be ingested in small amounts via water from aging pipes, as well as contaminated soil and dust. At very high levels, lead poisoning may result in seizures, coma or even death. However, long term, lower-level exposures are a more common health threat, particularly in children.
Read the full news release here.