Good column - last update was in 1997, though. Time for another update?
Also, it looks like the first paragraph of Cecil’s answer should be broken at the italicized words “The ‘amotivational syndrome,’” as the other particular health concerns of pot smokers similarly got their own paragraphs.
There was a BBC doku recently that adressed the risk of several drugs, listing them by their dangers (the ten or twenty most dangerous drugs?). They said that Marijuana while generally low risk for causing psychosis and schizophrenia, (about 1%), doubled the risk in narrow age of teenage years (13-17 years) and even more so in people with previous risk for schizophrenia (genetically). So their advice was to to smoke Hash during the teen years, because the risk increase was too high. They presume that when during teenage time the brain is partially rewired, the influence of Hash is much more disruptive than at other times.
Constanze - There is an old joke that goes around and around in the medical, health and drug agency world. You choose something, let it be carrots or mescaline, then you say that you have found that the users have about 1 % chance of psychosis and schizophrenia and that it should therefore be avoided. The joke is of course that this applies to roughly 1 % of everyone, with or without something that does not heighten the percentage.
Um, you seem to have misunderstood me. What the doku said was:
under normal circumstances, there’s a 1% chance of schizophrenia
research shows that teens who smoke marijuana double that chance
therefore, it’s advisable to not smoke marijuana during teen times (when your brain is partly rebuilding and therefore apparently more vulnerable than at other times); because you don’t know beforehand if you are in that risk percentile to start with.