Is pot good for you?

By 12th grade, about half of young Americans have tried marijuana, which put me in the geeky other half. I used to think this was a good thing, since I never developed a taste for pot and avoided becoming dependent. But as the medical-marijuana movement flowered and weed's p.r. improved, I often wondered if I shouldn't have relished it as a kid, before I had a personal trainer to tsk-tsk my every vice. Shrinking testicles? Mushy brains? I came to see these as grotesqueries invented by antidrug propagandists.