When a child first presents with symptoms of Attention Deficit Hyperactivity Disorder (ADHD), it is important to assess if there is an underlying medical cause for the symptoms. Lead is a neurotoxin that has been well studied to affect children’s cognition and behavior, and the behavioral profile seen with lead toxicity can mimic ADHD. Children with lead toxicity can have low IQs. Neurobehavioral symptoms seen with lead toxicity include: inattention, disruptive behavior, and hyperactivity.
Exposure to lead for children occurs primarily by: (1) lead paint in older houses, schools and other buildings; (2) lead from airborne pollution that has bound to soil and dust; (3) lead in imported products like toys, poorly regulated supplements, jewelry, etc; and (4) tainted water leaching from lead in pipes. Pica is a risk factor for lead toxicity. Lead’s negative effects on children’s development has been known for a long time, and lead use was finally restricted in the U.S. in the 1970s and phased out of gasoline and paint by 1986, although airplane gasoline is still leaded.
Studies have shown that lead affects the brain by causing disruption in the signaling of the prefrontal cortex and striatum. Epigenetics appears to be involved on the process of how lead exposure leads to symptoms of ADHD, and the effect on IQ seems to play a causal effect on the behavioral symptoms that are seen.
In 2012 the Advisory Committee on Childhood Lead Poisoning Prevention of the CDC changed the reference level for clinical intervention from 10μg/dL to 5μg/dL. Universal screening is not being practiced because clinical intervention for low-level exposure is limited. Rather targeted screening of at risk populations is being practiced with the option of more sensitive follow up tests if needed. Screening questions that can be helpful to determine if a child’s lead level should be tested includes:
1) Finding out how old the house is that the child lives in/school that child attends.
2) Asking about other sources of lead exposure (living near an airport; lead in toys, supplements, etc.)
At lower lead levels that are clinically significant (above 3 μg/dL), recommendations include to remove the source of lead exposure and retest, and to assess other nutritional factors, like iron and calcium. At higher lead levels, chelation can be used. Levels higher than 5μg/dL need to be reported to the CDC.
Reduction in lead exposure and therefore lead levels may not reverse neurodevelopmental effects that are seen, but it will prevent more negative effects on a child’s development. It is therefore important for a child presenting for the first time with symptoms of ADHD, to determine if an assessment for lead toxicity, as a possible contributor to the child’s presentation, would be appropriate.