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:
Attention-deficit/hyperactivity disorder (ADHD) or is it Attention Deficit Disorder (ADD)?
ADHD is a neural development disability which can be related to the brain function and behavior of an individual.
Individuals with ADHD are hyperactive, have trouble paying attention and are unable to control their impulses.
ADHD is a brain disorder which can interfere with the daily task at home or work. Both the terms ADD and ADHD refer to a syndrome found in both children and adults with visible characteristics by restlessness, hyperactivity or impulsiveness.
A few signs for individuals with ADHD can be seen as,
On the other hand, Attention Deficit Disorder (ADD) is an outdated term used for Attention Deficit Hyperactivity Disorder. This condition can vary from person to person and used to refer an individual who had trouble focusing on anything rather than being hyperactive.
ADD is a type of ADHD that doesn't involve constant movement and fidgeting. But it's a blurry distinction.
I have been treating ADHD and other vocational training for special needs at Accel Centre for the past 20 years and have realized that it is not a disability or deficit instead of a trait an individual can have with some positive and negative outcomes.
ADD is the term commonly used to describe symptoms of inattention, distractibility, and poor working memory. ADHD is the term used to describe additional symptoms of hyperactivity and impulsivity. Both are included in the medical diagnosis of ADHD.
1980-1989, Attention Deficit Disorder (ADD) 1997, Attention Deficit and Hyperactivity Disorder ADHD