Ji Y, et al. - The prospective associations between early childhood lead exposure and subsequent risk of attention deficit hyperactivity disorder (ADHD) in childhood and its potential effect modifiers were investigated. Researchers examined data from one thousand, four hundred seventy-nine mother–infant pairs (299 ADHD, 1,180 neurotypical) in the Boston Birth Cohort. They observed that elevated early childhood blood lead levels increased the risk of ADHD. They noted that boys were more vulnerable than girls at a given lead level and this risk of ADHD in boys was lessened by one-half if the mother had adequate high-density lipoprotein levels or low stress. These discoveries shed new light on the sex difference in ADHD and point to opportunities for early risk assessment and primary prevention of ADHD.