drug tolerance

While one study is certainly not definitive, this may explain a lot.  Thus far, the primary means of testing is still on rats.  It's high time we began some serious human trials on the effects of THC. Can I see a show of hands?

Females Build Up Tolerance To Marijuana Faster Than Males, Study Finds

Despite a shortage of research on the topic, it's been suggested that drugs affect men and women differently. And because of the recent legalization of recreational marijuana in Colorado and Washington and medical marijuana in 23 states, it's now more important than ever that women understand how THC affects their body chemistry specifically.

Researchers at Washington State University have found evidence indicating that females may build up a tolerance to marijuana more easily than males do.

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The study focused on the pain-relieving effects of THC on male and female rats. In this case, rats made for good subjects, because, like humans, rats have a menstrual cycle (albeit one that lasts four to five days instead of 28), and they experience similar ovarian hormone fluctuations, which affect pain.

At the beginning of the trial, the female rats displayed a higher sensitivity to THC than the males. However, after 10 days of testing, researchers found that the female rats were needing higher doses of THC than the males just to experience the same degree of pain relief. In other words, while female rats started out being more sensitive to THC, after 10 days, they ended up less sensitive.

More at link.