Curbing Mom's Smoking, Childhood Lead Exposure May Be Key to Preventing ADHD - US News and World Report Attention deficit hyperactivity disorder takes a huge toll on children, with about 9 percent of kids ages 8 to 15 displaying diagnosable symptoms of inattention, hyperactivity, and impulsive behavior that can make schoolwork an ordeal and friendships trying. Maternal smoking and lead exposure in early childhood might be behind nearly 40 percent of ADHD cases, according to new research. If that turns out to be true, it may be possible to prevent many cases of ADHD and reduce the huge social, financial, and personal toll of the disorder. While the cause (or, most likely, causes) of ADHD remains a mystery, we do know that it tends to run in families, so there's probably a genetic susceptibility. In addition, prenatal exposure to tobacco smoke and industrial chemicals and childhood exposure to lead have long been associated with attention problems and impulsivity. Both lead and tobacco alter how the brain uses the neurotransmitter dopamine, which helps control movement and emotion, and the brains of people with ADHD may be less sensitive to dopamine.