Russell Barkley's videos on YouTube are a good overview of the science.
ADHD is defined as a cluster of symptoms like many other disorders. Probably there are different etiologies. But the treatments are the same.
Mild ADHD was less of an impediment before industrialization. It's less of an impediment if you have a secretary at the office and a wife at home. Self medicating can help. And what does a severe case look like if you don't know what you're looking at? Maybe shiftless, maybe dim, maybe accident prone, maybe hot headed, maybe a drunk. So it's no surprise diagnosis varies.
ADHD is defined as a cluster of symptoms like many other disorders. Probably there are different etiologies. But the treatments are the same.
Mild ADHD was less of an impediment before industrialization. It's less of an impediment if you have a secretary at the office and a wife at home. Self medicating can help. And what does a severe case look like if you don't know what you're looking at? Maybe shiftless, maybe dim, maybe accident prone, maybe hot headed, maybe a drunk. So it's no surprise diagnosis varies.