Prenatal manganese levels linked to childhood behavioral disinhibition.

Although manganese (Mn) is an essential mineral, high concentrations of the metal can result in a neurotoxic syndrome affecting dopamine balance and behavior control. We report an exploratory study showing an association between Mn deposits in tooth enamel, dating to the 20th and 62-64th gestational weeks, and childhood behavioral outcomes. In a sample of 27 children, 20th week Mn level was significantly and positively correlated with measures of behavioral disinhibition, specifically, play with a forbidden toy (36 months), impulsive errors on a continuous performance and a children's Stroop test (54 months), parents' and teachers' ratings of externalizing and attention problems on the Child Behavior Checklist (1st and 3rd grades), and teacher ratings on the Disruptive Behavior Disorders Scale (3rd grade). By way of contrast, Mn level in tooth enamel formed at the 62-64th gestational week was correlated only with teachers' reports of externalizing behavior in 1st and 3rd grades. Although the source(s) of Mn exposure in this sample are unknown, one hypothesis, overabsorption of Mn secondary to gestational iron-deficiency anemia, is discussed.