How does one determine the "normal" levels of distraction/laziness from clinically diagnosable ones? Surely this is a spectrum. How does one determine the thres

How does one determine the "normal" levels of distraction/laziness from clinically diagnosable ones? Surely this is a spectrum. How does one determine the threshold? Is this just stats/distribution based? Does it vary from population to population? How much of this is nature vs nurture? Are there physical/neuro-structural/procedural differences in the brain? How do we know the so called medication isn't just treating the symptoms as opposed to solving the problem, if not causing more/other problems (kind of like anti-depressants)? How much do we actually know about all of this? I don't know any details about ADD/ADHD, but I can relate to a lot of these symptoms. I never once thought I had ADHD, but it would make sense that something like this is a spectrum rather than a binary property.