[MrLeRoy]

that those who began using cannabis as teens were four times more likely to suffer from psychiatric problems as adults than adolescents who did not use the drug.

Which can equally well be explained by the theory that the later psychiatric problems are already manifesting themselves in these teens and increasing their propensity to seek out marijuana.

[UKCajun]

Which can equally well be explained by the theory that the later psychiatric problems are already manifesting themselves in these teens and increasing their propensity to seek out marijuana.

That being the case, I doubt 1) it would have passed peer review muster for publication in the British Medical Journal and 2) other studies would confirm it.