The symptoms of ADHD in adults include poor concentration, being easily distractible, forgetful, but critically, those symptoms have to have been present since you were a child.
ADHD in adults is not something that develops suddenly at 18. If one looks back in the past, one can see these symptoms going back to childhood. In addition, hyperactivity can be present in a child, which may progressively disappear as you get older.
So the core symptoms are poor concentration, forgetfulness, a tendency to lose things. They equate to, in some people, adult ADHD.
Dr Matthew Cullen, Psychiatrist, St Vincent’s Hospital, Sydney