I like you being curious and asking the right questions. I think I can empathize with most things you said. I'm just a regular person, not diagnosed with anything. But I also can relate to caffeine, sugar, ... playing a role in my life. Maybe I'm not spot on 'normal' when it comes to impulse control or dopamine receptors myself. People are different anyways... I absolutely like(d) the kick I got from nicotine. I could afford it and judging by the studies I read, it's not that harmful. So I always continued. If I could just vape a bit in the evening on weekends, I'd certainly wouldn't see a reason to stop and happily continue as of today. But unfortunately I can't. I'd be full on addicted the next day.

I think there is a range of addictiveness. And it depends on the substance. How easy it lures you in, how severe the consequences and health effects are, and the withdrawal and how complicated it is to overcome the addiction. These are independant from another. I think nicotine scores quite high on the addictiveness (for some people). But I can only compare it first hand to everyday substances. I've never done hard drugs and weed only once or twice. But I've cut down on sugar or caffeine. I've also had headaches from caffeine withdrawal. But it was easier.

I think you can even smoke or vape and get away with it. You just need one of the few brains that are wired to allow this and impose strict rules on yourself to limit exposure. And judging by the people I know, odds are always against you.

I think I should buy a mountainbike and from now on get my dopamine rush from speeding through the undergrowth instead of abusing substances. I'm going to continue using caffeine, though... abuse sugar and a beer or two every now and then. I'm not perfect. And I don't strive for being a perfect human. Whatever that would be.