THC (Tetrahydrocannabinol) activates cannabinol receptors in one's brain whenever they smoke cannabis. These receptors are responsible to stimulating hunger (why you get munchies) but they also stimulate something called long term depression, which is the process by which your brain forgets memories. The effects take years to decades for anything significant enough to precipitate.
Now, I'm not against smoking cannabis just like I'm not against drinking alcohol. I'm for people understanding the risk factors and being fully informed before they make a decision.
I was going off my undergraduate neuroscience course when I asked my professor who has his doctorate in neurophysiology about long term cannabis use. Looking at Wikipedia (https://en.wikipedia.org/wiki/Long-term_effects_of_cannabis#...) you're right that it's fairly inconclusive and there may be some cofounding variables at play which are preventing us from assigning a firm sequela. Active cannabis users will have memory deficits.
They are trying to say that THC can cause depression, but it can take many years. I'm just clarifying (and not downvoting, like the rest of 'hacker' 'news'.. lol) and do not necessarily agree/disagree with OP
Now, I'm not against smoking cannabis just like I'm not against drinking alcohol. I'm for people understanding the risk factors and being fully informed before they make a decision.