Low blood lead tied to hostile, defiant behaviour in children
Low concentrations of lead (Pb) in the blood are associated with higher levels of oppositional defiant and hostile distrust behaviours in children, a new study shows.
Moreover, mercury (Hg) exposure is associated with vagal reactivity which may indicate an involvement in autism spectrum behaviours.
In the study involving 203 children (mean age 10.59±0.89 years) from mostly low-middle socioeconomic status (SES) families, increasing levels of Pb in the blood were associated with significantly higher child-reported total hostility (p=0.04) and hostile distrust (p=0.004) after accounting for race, gender, age and SES.
In terms of emotion regulation, child-reported total difficulty (p<0.10), poorer emotional awareness (p<0.05) and less emotional clarity (p<0.05) were significantly greater in the model that accounted for the covariates.
In contrast, when the parents were asked, blood Pb was associated only with significantly higher oppositional defiant disorder (ODD) behaviours (p=0.03) after controlling for covariates.
Blood Hg showed significant interactions with low frequency (LF; p<0.05) and low frequency to high frequency ratio (LF/HF; p<0.05) indicating that increasing blood Hg concentrations were associated with autism spectrum symptoms.
In terms of clinical cut-points, blood Pb and Hg did not show significant associations with ODD, Attention Deficit and Hyperactivity Disorder, autism and Asperger’s behaviours.
Whole blood samples were collected from participants and analysed for total Pb and Hg concentrations. Hostility, disruptive behaviours and emotional regulation were all measured using the appropriate questionnaires and scales. Electrocardiogram was used to measure interbeat intervals for the vagal responses to acute stress.