> The main players here are heroin (DEA sched 1), meth (2), cocaine (2), GHB/Xyrem (3), some benzos (4), tobacco (legal), and analogs therein. It's hard to have a casual habit with these drugs, as they manipulate the brain's behavioral calculus itself.
Caffeine, possibly. I have a pretty strong caffeine addiction myself. But the harm level of caffeine vs alcohol, tobacco, or anything else harder, is far far less.
Sugar, no, it doesn't bind to transduction receptors in the same way (it is rewarding, but not like "drugs" are).
Would caffeine and sugar also fall in this list?