Appeal to authority is a logical fallacy. The fact that they are well-credentialed does not excuse the fact that the study in question just flat-out isn't science. It's not reproducible without getting the same group back in a room together, it's based on subjective opinion or subjective interpretation of objective data, and it compares legal substances to illegal substances without offering a principled way to control for the effects of that regulation.

Do you really think the Lancet wants to get caught publishing highly controversial rubbish ("link bait")?

Um, The Lancet frequently publishes controversial articles. They published (and later retracted) a paper that claimed a link between vaccines and autism, they put out one of the highest death-toll estimates of the Iraq War, and they've called for a complete ban on tobacco products in the UK, to name a few.