A neurodevelopmental disorder characterized by persistent difficulty maintaining attention, focus, and concentration in the absence of hyperactivity. People with ADD may seem forgetful, easily distracted, or have trouble completing tasks. Unlike attention deficit hyperactivity disorder (ADHD), ADD does not include the impulsive or hyperactive behaviors that are characteristic of ADHD. The disorder is often diagnosed in childhood but can persist into adulthood, affecting academic performance, work, and social relationships.