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Rat Study: Females More Sensitive to Cannabis

Rat Study: Females More Sensitive to Cannabis

Due to higher estrogen levels, females are at least 30 percent more sensitive to the pain-relieving effects of THC (the active ingredient in cannabis) compared to males, according to a new rat study at Washington State University (WSU).

Females are also more susceptible to the negative side effects of cannabis — anxiety, paranoia, dependence — and may develop tolerance more quickly.

The “munchie effect” — the increased desire and need to eat — appears to be the only THC reaction where males show more sensitivity than females.

According to the researchers, most medical marijuana patients prefer a balance among the different cannabinoids. But when it comes to the recreational type, selective breeding has resulted in tetrahydrocannabinol (THC) concentrations double or triple those seen in the 1960s and 70s. THC is the psychoactive ingredient behind the characteristic mental high.

“Marijuana is very different than it was 40 years ago,” she said. “It’s much higher in THC and lower in cannabidiol, so a little bit goes a very long way,” said lead author Dr. Rebecca Craft, a psychology professor at WSU.

“We’re more likely to see negative side effects today like anxiety, confusion, panic attacks, hallucinations or extreme paranoia. And women are at higher risk.”

Most studies have been conducted on men due to their more stable hormonal profile. Craft, however, has been studying drug sensitivities in females for years.

Working with rats in her laboratory, Craft said she and her team “routinely manipulate hormones and follow females across their cycles to see if their drug sensitivities change along with their hormones. And they do…very frequently.”

“What we’re finding with THC is that you get a very clear spike in drug sensitivity right when the females are ovulating – right when their estrogen levels have peaked and are coming down,” she said.

In the current study, the researchers examined the pain-relieving effects of THC in male and female rats. After 10 days of treatment, tolerance to THC was shown to be much greater in females than males.

They also found that a low dose of THC did not disrupt the reproductive cycle in female rats, something that has been under debate, Craft said, but needs more study.

The researchers are also investigating the effects of cannabidiol, which can counter some of THC’s negative side effects. The THC and cannabidiol studies will be extended to include chronic types of pain typically seen in people who request medical marijuana, such as those with debilitating back or joint pain, cancer, Crohn’s disease, multiple sclerosis, severe muscle spasms and more.

“These people have pain that lasts for months or years,” Craft said. “Tolerance develops differently and sometimes you get a lot less tolerance to a drug when people are in chronic pain.”

The study is published in the journal Drug and Alcohol Dependence.

Source: Washington State University

Rat Study: Females More Sensitive to Cannabis

Traci Pedersen

Traci Pedersen is a professional writer with over a decade of experience. Her work consists of writing for both print and online publishers in a variety of genres including science chapter books, college and career articles, and elementary school curriculum.

APA Reference
Pedersen, T. (2018). Rat Study: Females More Sensitive to Cannabis. Psych Central. Retrieved on September 27, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 6 Sep 2014)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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