They are essentially the same diagnostic family, but ADD is an older term.
Historically, clinicians used ADD (Attention Deficit Disorder), especially for people whose main difficulty was inattention rather than obvious hyperactivity. Since DSM-III-R (1987), and in current DSM-5-TR terminology, the diagnosis is ADHD — Attention-Deficit/Hyperactivity Disorder.
ADHD is now described by presentations rather than by “ADD vs ADHD”:
- ADHD, predominantly inattentive presentation — distractibility, forgetfulness, disorganization, difficulty sustaining attention. This is what many people still casually call “ADD.”
- ADHD, predominantly hyperactive/impulsive presentation — restlessness, excessive talking, interrupting, difficulty waiting.
- ADHD, combined presentation — clinically significant symptoms from both groups.
So, in ordinary language:
ADD ≈ ADHD, predominantly inattentive presentation.
One important point, especially in adults: the word “hyperactivity” does not mean an adult must be visibly bouncing around the room. It may present as inner restlessness, impatience, excessive mental activity, frequent task-switching, or impulsive decisions.
And this connects directly with the issue we discussed previously: adult-onset attention problems are not automatically ADHD. For a formal ADHD diagnosis, DSM-5-TR requires that several symptoms were present before age 12, even if nobody diagnosed ADHD at the time. Sleep deprivation, depression/anxiety, substance use, digital overstimulation, medications, and other conditions can all produce an “ADD-like” phenotype.
So I would regard “adult ADD” as a colloquial description, not a separate modern diagnosis.
