Attention-deficit/hyperactivity disorder (AD/HD or ADHD) is a neurobehavioral developmental disorder. It affects about 3 to 5% of children globally with symptoms starting before seven years of age.

There is wide variability in estimates dependenting on research methodologies utilized in studies. It is characterized by a persistent pattern of impulsiveness and inattention, with or without a component of hyperactivity.

ADHD is diagnosed twice as frequently in boys as in girls, though studies suggest this discrepancy may be due to subjective bias. ADHD is generally a chronic disorder with 30 to 50% of those individuals diagnosed in childhood continuing to have symptoms into adulthood. As they mature, adolescents and adults with ADHD are likely to develop coping mechanisms to compensate for their impairment.