My ex explained ADHD to me this way. Paraphrased for clarity:
"Most people hear their own voice in their imaginations. 'What time is that appointment?' 'Remember to pick up fresh vegetables.' That's normal and ubiquitous. It helps people function efficiently by providing focus and by helping them to remember things. I hear my voice like that, too; except I hear multiple instances at once. There'll be six or twenty or forty trains of verbalized thought overlapping, interfering, and drowning each other out. Without Adderall I can sometimes focus on one train of thought to the exclusion of the others, following it to completion. But not usually. With Adderall the number of simultaneous iterations of my voice drops to two or three, or sometimes even just one. It's thanks to that clarity I was able to complete my university degree cum laude in just two years."
I thought to myself, So that's what that is, while simultaneously thinking Should I tell my psychiatrist about this? Should I ask her for Adderall?, and Why haven't I understood this earlier?, and Will I be able to function more effectively if she puts me on Adderall?, and I thought this was normal, I mean I thought everyone thought like this!, and Remember to pick up fresh vegetables.
Like depression, I'd worked out ways to work around what in hindsight I now understand to be a nontrivial hurdle. For current purposes the workaround to emphasize is vignette. It's much easier for me to write short scenes than extended narratives, because the narrative gets tangled in the Ligeti choir of multiple overlapping directions of thought. Even though I can focus effectively on one voice at a time, it jumps from thought to thought in a patchwork of associative leaps. On the one hand this leads to useful insights, where I'm constantly comparing and juxtaposing ideas, particularly if they're logically related. For example, identifying the Pascalian strains in Althusser's work. On the other hand it creates barriers to systematic exposition, because I'm thinking associatively rather than linearly. I struggle to translate to the more sequential mode of thought most people find intuitive.
Unfortunately, or maybe not, my psychiatrist won't put me on stimulants. It's unusual at this age, and my chart shows episodes of arhythmia which are counter-indications for Adderall. Of course, those arthymias occurred in the ER when I was defying Death while heroically battling severe sepsis. "Fuck you, Death," was one of my many simultaneous trains of thought, to which Death replied, "Oh seriously? Ha! Now you can't have Adderall, you addled fuck." Realistically we can probably call that round a draw, but it does mean that at least so far I manage ADHD without chemical assistance.
I'm not sure how much it matters. By this point I am what I am. It does mean I struggle to complete projects, including papers I've promised friends we'd co-author. I expect they're used to it by now, and I thank them for their loyalty despite me.