Attention deficit hyperactivity disorder (ADHD), also referred to as Attention Deficit Disorder (ADD), is one of the most common childhood conditions that involve behavioral symptoms such as inattentiveness, hyperactivity and impulsiveness. Although the condition may begin during childhood, it can continue through adolescence and adulthood. Signs of ADHD include a short attention span or being easily distracted, restlessness, constant fidgeting or overactivity and being impulsive. ADHD can be hard to diagnose and even harder to understand.