Attention-Deficit/Hyperactivity Disorder 61
Severe:  Many symptoms in excess of those required to make the diagnosis, or several
symptoms that are particularly severe, are present, or the symptoms result in marked
impairment in social or occupational functioning.
Diagnostic Features
The essential feature of attent ion-deficit/hyperactivity disorder (ADHD) is a persistent
pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or
development. Inattention  manifests behaviorally in ADHD as wandering off task, lacking
persistence, having difficulty sustaining focus, and being disorganized and is not due to
defiance or lack of comprehension. Hyperactivity  refers to excessive motor activity (such as
a child running about) when it is not appropriat e, or excessive fidgeting, tapping, or talk-
ativeness. In adults, hyperactivity may manife st as extreme restlessness or wearing others
out with their activity. Impulsivity  refers to hasty actions that  occur in the moment without
forethought and that have high potential for harm to the individual (e.g., darting into the
street without looking). Impulsivity may reflec t a desire for immediate rewards or an in-
ability to delay gratification.  Impulsive behaviors may manifest as social intrusiveness
(e.g., interrupting others excessively) and/ or as making important decisions without con-
sideration of long-term consequences (e.g., taking a job without ad equate information).
ADHD begins in childhood. The requirement that several symptoms  be present before
age 12 years conveys the importance of a substantial clinical presentation during child-
hood. At the same time, an earlier age at onset is not specified because of difficulties in es-
tablishing precise childhood onset retrospectively. Adult recall of childhood symptoms