Freaked me out.
Upon closer inspection, the study has some serious flaws. For one thing, there are only 15 participates, only from the ages of 15 to 18. The fact that they smoked every day for a year also creeps me out, particularly when they're that young. I'm not against smoking pot, but I don't think 15 year old kids should be smoking, because they're too impressionable, and from kids I've known, start smoking way too much, and let it get in the way of school and the like. On the other hand, kids who started smoking pot after high school generally know how to behave responsibly and still finish homework and do productive things. The chronic stoners I knew in high school cut classes all the time and didn't even make it to college.
Also, the kids had only quit smoking for a month, which isn't necessarily enough time for cells to regenerate, etc. I that since this is such a new study, they should probably do a similar study with former smokers, and by former I mean people who haven't smoked in say, 5 or 6 years. Other studies have shown that after about a week or two of non-smoking, the mental capacities of people who have smoked pot are the same as non-smokers, and after 1 or 2 days, they're almost the same, and the only difference is a slightly reduced ability to concentrate.
Obviously the effects are not the same as schizophrenia, because I'm certainly not having any hallucinations right now. And neither are those 60 year old ex hippies. Well, maybe if they did acid.