Is ADHD a mental illness or disability?

Strictly speaking attention-deficit hyperactivity disorder (ADHD) is neither a mental illness nor disability. Attention problems include daydreaming, difficulty focusing and being easily distracted. Hyperactivity refers to fidgeting or restlessness. A person with the disorder may be disruptive or impulsive, may have trouble in relationships and may be accident-prone. Hyperactivity and impulsiveness often improve as a person matures, but attention problems tend to last into adulthood. Children with ADHD are more likely to have learning issues.