Cannabis study suggests women may need less THC to get to the same effects as men

Women tend to experienced the same acute effects of cannabis as men at a lower dose of THC, according to new research published in Psychopharmacology which sought to mimic real-world smoking practices.

“We know from population survey data that men are more likely to use cannabis than women, but it seems like women experience more severe cannabis-related harms,” said study author Justin Matheson, a PhD candidate at the University of Toronto.

“Research in animals suggests that this is because females are more sensitive to the effects of THC, the primary psychoactive compound in cannabis, and that this might be due to differences in the way THC is metabolized in females. However, there has been relatively little human laboratory evidence to suggest sex differences in the acute effects of THC.”

In the double-blind study, 91 healthy cannabis users smoked a single cannabis cigarette (12.5% THC or placebo) before completing subjective effect scales and cognitive tests. The researchers also monitored their vital signs, such as blood pressure and body temperature. The participants used cannabis about 1 to 4 times per week and were 19 to 25 years old.

The researchers found that female participants tended to smoke for just as long a duration as males. However, women tended to smoke less of the cannabis cigarette.

Despite the differences in cannabis consumption, there were no differences in peak subjective drug effects, mood or cognitive effects between men and women.

“We found that women smoked less of a cannabis joint, had lower levels of THC in blood, yet experienced the same acute effects as men. So, I think the main take-away is that women may need a lower dose of THC to get to the same degree of intoxication as men,” Matheson explained.

“What I want to stress here though is that, in our study, participants were able to smoke the amount of cannabis they wanted to. When participants smoke to their desired high, we call this ‘titrating to effect.’ Titrating to effect is possible when smoking cannabis because THC delivery to the brain is very rapid with this route of administration, so users can feel the high as they are still smoking.”

“However, with other cannabis products like edibles or beverages that have a delayed onset of action, it is not possible to titrate to effect. In these cases, women are likely at higher risk of experiencing acute harms,” Matheson told PsyPost.

Like all research, the study includes some limitations.

“The major caveat here is that we considered sex as a binary biological variable (male vs. female) and we had no measure of gender. Sex is a biological construct that represents things like sex chromosomes, hormones, anatomy, and physiology, while gender is a social and cultural construct that represents things like our gender identity (male, female, or gender-diverse) and the expectations that our societies have for us based on these identities,” Matheson said.

“Studies like ours represent sort of the first step to observing that there are sex differences in the acute effects of cannabis. But the next step is to see why that is the case, and the answer likely involves both sex and gender. For example, there’s evidence that estrogen (a sex hormone) influences the metabolism of THC, which could explain some of the sex differences in the metabolism of THC we see. But we also know that gender identity influences drug use behaviors, which could relate to why we saw that women smoked less of the cannabis joint.”

“Something important that I think not a lot of people are aware of is that women and female animals have been excluded from biomedical research for much of the history of science. As a result, our understanding of human health and disease is biased towards males. Thankfully, most major funding agencies have adopted policies requiring females to be included in research, and I hope as a scientific community we can further improve on these policies to incorporate more comprehensive measures of sex and gender,” Matheson added.

The study, “Sex differences in the acute effects of smoked cannabis: evidence from a human laboratory study of young adults“, was authored by Justin Matheson, Beth Sproule, Patricia Di Ciano, Andrew Fares, Bernard Le Foll, Robert E. Mann, and Bruna Brands.