Atypical Neuropsychological Profiles, Attention Deficit Disorder, Brain Anomalies and Environmental Insecticide Exposure

Background: Underlying variability in neuropsychological profiles has been demonstrated among children with attention deficit disorders, and this may contribute to the differences in behavioral phenotype and clinical disorders in this population.

Objectives: This study investigated the contribution of prenatal exposure to chlorpyrifos, a widely used organophosphate pesticide, to neuropsychological patterns and clinically defined ADHD-type outcomes at 12 years of age. Observed patterns were associated with anatomical MRI findings.

Methods: An inner-city community-based cohort was followed prospectively from the prenatal period through 12 years of age (n=250), including repeated biomarkers of environmental exposures, full neuropsychological test battery, and structural MRI.

Results: Highly exposed children showed a unique neuropsychological profile, with significant deficits (all ps<0.01) in auditory attention and fine motor performance, but no deficits on more complex visual attention and inhibitory control tasks. Children with pesticide exposure and the signature profile were at increased risk of clinically-meaningful ADHD, as measured by the DuPaul-Barkley ADHD Rating Scale. These findings were consistent with abnormalities in morphological measures of the cortical surface, including the posterior temporal region, subserving attention and receptive language.

Conclusions: Findings suggest that prenatal organophosphate pesticide exposure, at relatively modest doses common in agricultural regions of the US, result in a signature pattern of neuropsychological deficits, accompanied by disturbances in brain morphology by MRI, persisting into the early school years. Furthermore, highly exposed children with this atypical profile were at significantly increased risk of ADHD-type symptoms.