Patrick Kennedy's SAM spam, redux

[RainDog]

12. FACT: Marijuana and IQ

IQ tests themselves are debatable, but let's not go there. Let's focus on whether or not marijuana use causes lower IQ. (This is one of SAMs claims.)

This study from the Canadian Medical Association indicates that dose and frequency are the issue.

http://www.cmaj.ca/content/166/7/887.abstract

Results: Current marijuana use was significantly correlated (p < 0.05) in a dose- related fashion with a decline in IQ over the ages studied. The comparison of the IQ difference scores showed an average decrease of 4.1 points in current heavy users (p < 0.05) compared to gains in IQ points for light current users (5.8), former users (3.5) and non-users (2.6).

This study did not have a huge sample size, but the most astonishing result, it seems, is that light marijuana use resulted in a gain in IQ that was greater than the loss in heavy users and greater than the gains from either former users or non-users.