This is a interesting one. I once heard a psychiatrist ask someone during an evaluation: have you ever borrowed Ritalin from your friends? Follow up question: did it work?

I guess this is a really nice hack he had: Has used Ritalin illegally? Increased probability of ADHD. Does it work? Even more increased probability and he know knows the person tolerates it.

This fascinates me. Some people seriously take stimulants at night to fall asleep, others in the morning to wake up..!

Recently I heard the story about how stimulants came to be used to treat ADHD and one thing that stood out except that this was an extremely suprising effect was the very simplified explanation that stimulants seems to stimulate the inhibitory parts of the brain most which seems to account for the increased self control.

As someone who has just gone through the ADHD diagnostic process in the UK - previously abusing stimulants is a risk factor they have to consider before prescribing you anything.

I have previously used Modafinil fairly extensively and considered purchasing Ritalin or Adderall on the dark web, but was very worried about telling the doctor in case it would cause me issues getting treatment.

There’s a genetic component - don’t remember which gene, but only some are subject to its effects.

Brand can affect this according to anecdotes on /r/modafinil/