I meant, first, it's about tobacco and not nicotine, and second, it's a longitudinal correlational study, not causal as your link immediately jumps to (it "creates" a vulnerability).

The sleeper effect held true even if you controlled for gender, ethnicity, socioeconomic status, parents' smoking, and conduct problems

is not nearly enough to claim you have screened off all possible variables and now you are entitled to infer causation. (And the claim is pretty dubious in the first claim: one cigarette does all that? Even stuff like heroin doesn... (read more)