ADHD stands for Attention Deficit Hyperactive Disorder, with the main symptoms being visible hyperactivity and/or impulsivity while ADD stands for Attention Deficit Disorder with the main symptoms being inattention. Adult ADD/ADHD, as in children, is characterized by excessive inattentiveness, impulsiveness and hyperactivity. While in children, hyperactivity is often displayed as constant squirming and moving, in adults it may be more of a constant feeling of restlessness and agitation.
