A lot vs. Alot: 9 Grammatical Pitfalls
(abbreviated ADD) became a diagnosis in the third edition of the "Diagnostic and Statistical Manual of Mental Disorders" (1980); expanded to attention deficit hyperactivity disorder ("the co-existence of attentional problems and hyperactivity, with each behavior occurring infrequently alone;" ADHD) in DSM-III (1987).
attention deficit disorder at·ten·tion deficit disorder (ə-těn'shən)
A childhood syndrome characterized by impulsiveness and short attention span, and sometimes by hyperactivity that often leads to learning disabilities and various behavioral problems.
A disorder characterized by a difficulty in retaining focus, especially on tasks, for long periods of time.
Note: One of the most common reasons children are brought into therapy, ADD is often treated with the somewhat controversial drug Ritalin®, which is thought to work by stimulating the attention-focusing structures of the brain.