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Childhood Lead Exposure Found to Be Positively Associated With ADHD Diagnosis
Exposure to lead during childhood, but not prenatal exposure, may increase the chances of subsequent attention-deficit/hyperactivity disorder (ADHD) symptoms and diagnosis, according to results from a systematic review and meta-analysis published in Prevention Science.
“Our findings provide further support for negative impacts of prenatal and/or childhood exposure to certain chemicals and raise the possibility that primary prevention and targeted screening could prevent or mitigate ADHD symptomatology,” said Lina V. Dimitrov, MPH, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, and co-authors. “Furthermore, these findings support the need for regular review of regulations as our scientific understanding of the risks posed by these chemicals evolves.”
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The meta-analysis included results from 66 studies that examined the association between early chemical exposures and later ADHD symptoms or diagnosis. The papers included were published between 1975 and 2019, and examined the following chemical exposures: anesthetics (n=5), cadmium (n=3), hexachlorobenzene (n=4), lead (n=22), mercury (n=12), organophosphates (n=7), and polychlorinated biphenyls (n=13).
Analyses were conducted for each chemical exposure according to type of ADHD outcome reported (categorical vs. continuous), type of ADHD measurement (overall measures, symptoms only, diagnosis only, inattention only, hyperactivity/impulsivity only), and timing of exposure (prenatal vs. childhood vs. cumulative).
Childhood lead exposure was positively associated with ADHD diagnosis and symptoms across all analyses except for prenatal analysis (odds ratios [ORs] ranging from 1.60 to 2.62; correlation coefficients (CCs) ranging from 0.14 to 0.16). The authors also identified significant associations with organophosphates (CC=0.11, 95% CI: 0.03-0.19 for continuous measures of ADHD outcomes overall), polychlorinated biphenyls (CC=0.08, 95% CI: 0.02-0.14 for continuous measures of inattention), and mercury exposure during prenatal and childhood periods (CC=0.02, 95% CI: 0.00-0.04 for continuous measures of ADHD outcomes overall for either exposure window).
This study was administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and the CDC.
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