Is there a difference between ADD and ADHD? These terms are often used interchangeably. 

Is there a difference?
They are interchangeable.  ADD was a term used throughout most of the 80s and ADHD aftewards.  In the Diagnostic and Statistical Manual of Mental Disorders 1980 (DSM-III) published by the American Psychiatric Association (APA) it was named ADD and the name changed to ADHD in the 1987 edition, DSM-III-R (which I can find no online sources of).

ADD has been used to describe a sufferer without the observable hyperactivity but it is still essentially the same thing.  Which leads to the confusion.

Terms used to describe the condition include:


Before 1980, hyperkinetic reaction of childhood
1980-1987, Attention Deficit Disorder (ADD)
1987, Attention Deficit and Hyperactivity Disorder ADHD
1994, ADHD was disected into subtypes, predominantly inattentive (ADHD-PI or ADHD-I), predominantly hyperactive-impulsive (ADHD-PH or ADHD-HI), and combined type (ADHD-C).