AHA!

I've got it figured out now. (see previous post) We need to start with the assumption that pot makes you stupid. Now consider that based on the data from the Greek study, the mean IQs across all 3 study groups (long-term cannabis users, short-term cannabis users, and a "control" group of non-users) were for all intents and purposes identical (slightly above 100, small standard deviation, and the mean of any group is within one SD of the mean of any other group), the only conclusion that can be drawn is that the people that smoke pot started out smarter than the people who don't smoke pot. Maybe they're trying to find a way to relate to (or deal with) the vast numbers of insipid, knuckle-dragging morons that make up the bulk of the population.