For children with a particular gene mutation, just minimal exposure to lead may contribute to symptoms of ADHD, according to a new study published in the journal Psychological Science.
“This research is valuable to the scientific community as it bridges genetic and environmental factors and helps to illustrate one possible route to ADHD. Further, it demonstrates the potential to ultimately prevent conditions like ADHD by understanding how genes and environmental exposures combine,” said lead researcher Dr. Joel Nigg, professor of psychiatry and behavioral neuroscience at the Oregon Health and Science University (OHSU) School of Medicine.
For the study, researchers measured lead blood levels in 386 healthy children aged six to 17. Half of the children had been 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 findings revealed a stronger connection between lead exposure and ADHD symptoms — particularly hyperactivity-impulsivity — in children with the HFE C282Y gene mutation, present in approximately 10 percent of US children.
“Because the C282Y gene helps to control the effects of lead in the body and the mutation was spread randomly in the children, the findings of our study are difficult to explain unless lead is, in fact, part of the cause of ADHD, not just an association,” explained Nigg.
The findings also showed that lead effects were exacerbated in males, which is consistent with previous research specific to neurodevelopmental conditions and gender. Children without HFE C282Y mutations also showed amplified symptoms as lead exposure increased, but not as consistently.
The researchers do not suggest that lead is the only cause of ADHD symptoms, nor does the study 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 symptoms of ADHD.
While government regulations have drastically reduced environmental exposure to lead, the neurotoxin is still found in common items such as children’s toys and costume jewelry, and continues to be ingested in small amounts via water from aging pipes, as well as contaminated soil and dust.
“Our findings put scientists one step closer to understanding this complex disorder so that we may provide better clinical diagnoses and treatment options and, eventually, learn to prevent it,” said Nigg.