We're just problem solving here - the moral assessment of any given solution is each individual's choice to make, pal.
I really can’t wrap my mind around someone suggesting a drug addiction (that leads to cancer) to remedy a mental disorder. It’s just plain malicious.
If somebody is opening their mind to help, you have a responsibility as someone of greater knowledge to steer them in the right direction, not take advantage of them.
Check out this cool write-up: https://www.gwern.net/Nicotine
I think one thing to keep in mind is that Gwern is evaluating it for much more minimal use than you would try to treat adhd with. Iirc he was using it to try to build an exercise habit. So the addiction risks are going to be much higher than what he portrays them as.
Still better than untreated adhd though.