Marijuana Tolerance May Build Up Faster in Females, Rodent Study Suggests

Females may build up a tolerance to marijuana faster than males do, a new study of rodents suggests. People with an increased tolerance to drugs may be more likely to become addicted, The Huffington Post reports.

The study looked at the pain-relieving effects of marijuana’s psychoactive ingredient, THC. The researchers found that at the beginning of the study, female rats were more sensitive than male rats to THC. After 10 days, female rats needed higher doses of THC in order to experience the same degree of pain relief.

Female rats’ increased sensitivity to THC is due to their estrogen levels, lead researcher Rebecca Craft, Chair of the psychology department at Washington State University, noted in a news release. She found the rats were at least 30 percent more sensitive than males to the pain-relieving qualities of THC.

“We were looking at the pain-relieving effects,” Craft said. “One of the things that is of concern if you’re using any medication repeatedly is: Will it maintain its effectiveness over time?”

Craft said she would like to see a similar study conducted in people. “There are some differences in the species in terms of how they metabolize drugs,” she said. “You really want to see some kind of confirmation that the same thing is happening in humans.”

The study appears in Drug and Alcohol Dependence.