I point out, that as heartsurgeon claims, this study is a product of medical science, was published in a scientific journal, may have met some somewhat unknown peer review criteria, and now all issues regarding validity, including possible flawed public health data should be on the table.
But I also point out that this is a product of medical science and may or may not be the best state of the arts medical knowledge can produce today. And what medical science knows is always a time dependent moving target. I also point out that before the invention of the microscope, medical science was in a pitiful state of knowledge. And medical authorities far smarter than heartsurgeon were evolving long, complex, and learned theories based on philigious humors and similar mumbo jumbo. Then came the invention of the microscope and suddenly medical authorities were SEEING entire worlds of knowledge they had no idea even existed before. And even the dumbest of doctors could then make advances in medical knowledge that their smarter predecessors could never make---simply because they were blind to the existence of worlds we now see.
But the other point to make is that scientific methodology is the means that scientists in general see. And to advance, science can only rely on clear pictures. And when science starts to rely on vague pictures they in essence start hallucinating. And then can never be sure if they are seeing something real or not. And I hope that all can agree that the study being cited does not even fall into the class of a clear window---its more of an opaque and frostie lens that is almost 100% likely to be an optical illusion. There is nothing wrong with asking the question or testing the hypothesis that cannabis use can cause mental illness. The problem is in assuming that this study is going to be anything remotely resembling anything anyone can base a valid conclusion on.
In short----todays medical science can do better than that.----way way way better.
And pardon me for guessing on no evidence that this report will get attacked in the medical community. But we could be talking about six months or more for the attacks to get into journals. But if I can be so bold as to ask---heartsurgeon, especially if these attacks become accepted medical fact, will you then come back and issue the retraction responsible science usually expects from anyone who wants to maintain their credibility?
And cheer up---IF your peer reviewers and Lancet journal get really discredited for putting their names on a piece of garbage, which medical science is now honor bound to do IF they over reached, you almost better beat us nay sayers to the punch because you don't want to have us do it for you.