The association between environmental lead exposure with aggressive behavior, and dimensionality of direct and indirect aggression during mid-adolescence: Birth to Twenty Plus cohort.

Chronic lead exposure is associated with neurological ill-health including anti-social behavior such as aggressive behavior. The main aim of this study was to examine the association between lead exposure at 13years old and dimensions of aggressive behavior during mid-adolescence. The study sample included 508 males and 578 females in mid-adolescence (age 14 to 15years) from the Birth to Twenty Plus cohort in Johannesburg, South Africa. Blood samples collected at age 13years were used to measure blood lead levels. Seventeen items characterizing aggression from the Youth Self Report questionnaire were used to examine aggressive behavior. Principal Component Analysis was used to derive composite variables from the original data for aggressive behavior; and data were examined for an association between blood lead levels and dimensionality of direct and indirect aggression and disobedience during mid-adolescence. We also examined the dimensions of aggression during mid-adolescence in relation to gender and socio-demographic factors. Blood lead levels ranged from 1 to 28.1μg/dL. Seventy two percent of males and 47.7% of females in the study had blood lead levels ≥5μg/dL. There was a positive association between elevated blood lead levels and direct aggression (p<0.05). Being male was positively associated with direct aggression (p<0.001) but, negatively associated with indirect aggression (p<0.001). Maternal education and age at birth were negatively associated with direct aggression during mid-adolescence. The significant association between elevated blood lead levels and direct aggressive behavior observed in this study may shed light on a possible environmental toxicological contribution to aggressive behavior in South African youth; and most importantly the type of aggressive behavior associated to lead exposure.