Except hyperactivity is not a defining feature of the cluster. This belief, in fact, has historically biased practitioners against correctly diagnosing women with ADHD because ADHD tends to present differently in women. And to call the relationship of a person with ADHD to their attention a “lack” is a massive oversimplification. Sometimes we have too much attention and hyperfocus on a single thing for what neurotypical people consider an unusual amount of time. That’s just as much a part of my ADHD as are the moments where I “lack” attention. The defining feature is a disorder in dopamine regulation.

[–] Zagorath@aussie.zone 2 points 3 days ago

It's funny cos when I was young I recall it being called (at least sometimes) ADD. So the H has been added (or made mandatory in the name) at a time when we're realising that hyperactivity is not a necessary symptom.