Young cannabis smokers run risk of lower IQ

[Blizzard]

There's an interesting study about how cannabis consumption on teenagers younger than 18 years can cause a drop in IQ of an average of 8 points.

http://www.bbc.co.uk/news/health-19372456

[G_G]

Ha! And all my friends who do it, who tried getting me to do it, said it wouldn't affect me. Faggots. I'm now gonna go rub this into their faces. Thank you Blizzard for finding this.

[Subsonic_Noise]

I've been smoking marihuana for a long while. Average in college: 87-95%
My sister was an even more regular consumer. Finished her school top of class, won two prices and is studying medicine right now.
A friend of mine has been smoking for many years and is a brilliant psychologist right now, one of the most intelligent people I know, and also graduated top of class at my university.
8 points is within the inaccuracy of even a professional IQ test. I could take one two times in a row and get less or more the second time. It's affected by many different things, among them mental state, mood, time of the day, motivation, etc. I won't deny that there's some people out there who're getting negative effects from weed (because they simply overdo it), but please don't generalize. This study isn't representative at all. You wouldn't wanna take what extreme drinking does to people and apply it to everyone who drinks every once in a while. Same thing. I'm not gonna say Blizzard has a brain damage because he likes alcohol every now and then.

[winkio]

I am never one to trust medical studies, because they so often do not take into account all the factors present.  While I personally think that long term drug use could cause a decline in mental ability, there is nothing scientific saying it is either safe or unsafe, and this study certainly does not convince me.  One thing that does have a mountain of scientific evidence supporting it is that smoking of any sort leads to numerous health risks, so I can say with some certainty that while it is uncertain if marijuana has any risks, smoking marijuana is bad for your health.

[Blizzard]

This is just one study, there'd have to be many more in order to be more certain of these claims obviously and 8 points doesn't matter much to someone with an IQ of 150 (you're considered gifted if you're above 130). I'm just pointing out that there are studies and possibilities.
Besides that, somebody being smart doesn't necessarily mean they they have good grades and vice versa. I'm probably smarter than my sister, but my sister has better grades than me because she works for it more than I used to do when I was in school.

Also, there have been several studies that showed that drinking alcohol does not kill brain cells. I would have been the first to say that they do since I was a bit off during a time where I drank at least once a week and I really thought my IQ may have dropped until I realized that I only got lazy and I was as smart as always. >.< Don't ask. >.<

Apart from all that, fact is that some people get more into being drunk/high than they actually are. So there's a possibility of people faking it (probably without knowing it), too.

[Subsonic_Noise]

Also, there have been several studies that showed that drinking alcohol does not kill brain cells.

And there is studies saying that it does, and studies that say weed doesn't affect IQ negatively. I honestly wouldn't trust any of that.
And about the grades, it's a bit different in our college because we don't get your typical "repeat the stuff you learned" tests, but we get confronted with entire new situations, and we have to be able to dynamically adapt and have high problem solving skill. One way or the other, I wouldn't take this study seriously, same as for many others in the field. As I said, overdoing something nearly always does harm, but this seems more like an anti-weed campaign than anything else.