Alceste
Vagabond
what about this from your link
fail
Results: Current marijuana use was significantly correlated (p < 0.05) in a dose- related fashion with a decline in IQ over the ages studied.
That's more than 5 joints a week. Current potheads who smoke less than 5 joints a week experience a similar INCREASE, and the highest IQ increase out of the entire group, including non-users.
Read a little more carefully. Don't just look for a single sentence that you think backs you up.