According to the National Institute of Mental Health (NIMH), between three and five percent, or about two million American children have ADHD. A quarter of them have a close relative with the disorder, meaning it can be an inherited condition. Other potential causes include impaired brain function (especially in the frontal lobe) due to unknown causes, or possibly a mother’s use of tobacco, narcotics or alcohol during pregnancy and exposure to toxins such as PCBs and lead during childhood. In the majority of cases, symptoms become apparent during preschool years, and often persist throughout adulthood.

Children with ADHD suffer from a group of disorders that include hyperactivity, inattentiveness and impulsiveness. According to the NIMH, there are three main types of ADHD: predominantly hyperactive-impulsive (they don’t have attention problems), predominantly inattentive (they’re not hyper or impulsive) and a combination of the two. In general, boys are three times more likely to have ADHD than girls and they tend to suffer from the hyperactive-impulsive form while girls struggle more with inattentiveness.