Studies can prove whatever you want, depending on what you want.
I can only tell you this from personal experience: pretty much every person Ive known over the last 30 years who have used regularly, it made them stupid and lazy.
Like, very consistently.
In my own immediate family and my brothers kids, all but 3 individuals are college graduates.
Yep, those 3 were the only ones who smoked pot.
Believe what you want and have fun.
Not me. I enjoy life enough without having to seek an alternate reality.
Negative Ghost Rider, the pattern is full!
First of all, that's why I pointed out AND linked the journal article. JAMA does not have an agenda. They are interested in answers and science. Period. They are very concerned with the quality of the articles that they print and as usual this one has solid methodology behind it.
Second, allegorical evidence is not scientific evidence. I'm not dismissing your personal observations, but this metadata study examined literally thousands of peoples results with pre and post testing. Their results show little effect in brain function. Your observations are simply that... observations. Perhaps a lot of the stupid and lazy people that you know smoke pot. That's not the same as pot making them stupid and lazy.
As an example, take the recent autism scares associated with the MMR vaccines. Autism generally shows up in kids shortly after 2 years old. Kids get their MMR vaccines at this age. Some folks put these two things together and came up with the conclusion that these vaccines were causing Autism. Although this myth has been thoroughly debunked, some folks still believe it.
Same thing with your immediate family. Non college graduates have higher rates of substance abuse (both legal and illegal). I'd suggest that whatever made them non graduates also made them more likely to smoke pot. Both my brothers and I smoked pot in high school and are all college graduates and have good jobs and stable families. Should I think that pot smoking helps you graduate college and have a good life? Of course not... pot had NOTHING to do with that. I will admit that walking around stoned all day (or drunk, or high on pain meds) is not going to help you succeed. Addiction is a whole different animal. That's a completely different thing that this study does not address.
Finally, I don't know what you think pot does, but it is NOT LSD. There's no alternate reality any more than there is when you drink a couple of beers or a shot or two of liquor. You get a nice buzz, its lasts for a while, and then you come back down. In other words, it's nice to do at a party or after work or on the weekends. FYI, I've also never killed anyone, got in a fight, or generally gone insane while high either. That movie Reefer Madness is not real man.