“ADHD is what we would call a clinical diagnosis,” says Dr. Candida Fink, a board-certified child, and adolescent psychiatrist. “It’s a neurodevelopmental disorder that presents before age 12, and it includes a collection of signs and symptoms, both reported and observed, that occurs for a long enough duration that they come together to create a syndrome. Most importantly, it affects function.” Based on symptoms (which can be seen here), there are three types of ADHD presentations: 1) inattention, 2) hyperactivity and impulsivity, and 3) combined, in which a patient presents symptoms of both inattention and hyperactivity-impulsivity. To meet the criteria for the first two presentations, patients must exhibit six or more symptoms from a specified set. For the combined presentation, they must exhibit six or more symptoms from each category. For older teens and adults who present ADHD-like symptoms, doctors will typically place an ADHD diagnosis lower down on the list of possibilities. “More often, we find that people who present in adulthood have had issues for years but learned to compensate for them, or the issues were not causing a functional deficit,” says Dr. Fink. In some cases, the patient could be suffering from a progressive neurological disorder, a depressive episode, substance abuse, trauma, or another issue that’s impacting their attention.