I am not sure that this study demonstrates causation, but most of the comments here reek of motivated reasoning.
https://www.drugabuse.gov/publications/research-reports/mari...
We wont know for sure until this bigger study is done, but if you care about your brain you probably should stop with cannabis until we know its safe:
https://www.drugabuse.gov/drug-topics/adolescent-brain/longi...
I dont think we should compare the two so blithley. We have very strong evidence alcohol and tobacco is super bad for you, especially if you use it constantly. We have what is basically conjecture, rat studies, and correlation that doesnt paticularly control for confounding factors for marijuana [despite a concerted political effort to make it scary]. That doesn't make it "safe" but its just as wrong if not more so to say its comparable to things which we are very sure are unsafe.
Around drugs there is no dispassionate reasoning these days.
We know there is an effect. That's why people use them. Seems to miss the point to just say "this is harm" and ignore whatever factors would influence the decision to use.
Why is that prescription drugs come with a long list of "side effects" but most of society doesn't see the "harm" in those?
I imagine a lot of it is due to many prescription drugs not being habit forming or generally pleasurable, thus people are more likely to use it in cases where the benefit outweighs the harm in a much more objective fashion.
Your answer just further illustrates my point.
Have you ever been cycled through different antidepressants? Anti anxiety meds? ADHD meds? Meds for sleep, meds for wakefulness?
These drugs are all very potent and your body cannot distinguish between intended and so-called "side" effects.