In a Canadian survey, Tu et al (2008) examined correlates of cannabis use among 7th through 12th graders in British Columbia. They found that 14.3% of boys and 8.7% of girls met their criterion for "heavy" marijuana use: 10+ instances in the past 30 days. Most predictors were shared between sexes; ethnicity predicted use only for boys, while poorer mental health predicted use for girls. In the U.S., Kerr et al (2007) found that marijuana use had declined among men 18-25 since 1984, but had not among women, leading to convergence near 20% of people in this age group using within the past year by 2000; a similar convergence occurred in adults over 26, around 5%.
Interestingly, McGregor and Arnold (2007) found that female rats self-administered intravenous THC at a greater rate than males, and that this effect disappeared with ovarectomy. The authors argue that this could point to a estrogen-mediated reward system for the active compound in cannabis.
You know, the age 26 cut-off seems "right" to me. When I find out someone my age uses marijuana, I find myself adding the word "still" to that sentence: "she still smokes pot." I don't use the word "she" as a generic pronoun. I'm having trouble coming up with any man I know well who uses marijuana after age 25. I can think of several women, and they all seem to use it responsibly. However, one of my comic weaknesses is that I can't actually tell when people are under the influence of just about anything: my drug-dar is as faulty as my gaydar. So, it's entirely possible that half my friends are permanently stoned, but I just haven't noticed.
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