Men who use cannabis occasionally reacted more strongly to smoked cannabis than women with similar use habits, even though the amount of THC in their blood was about the same. This finding runs counter to earlier research suggesting that women are more sensitive to cannabis.
The study, published in Neuropsychopharmacology, is the first experiment designed to test how sex and frequency of use together shape the short-term effects of smoked cannabis. Researchers at the UCLA Center for Cannabis and Cannabinoids enrolled healthy adults, split evenly by sex and by how often they used cannabis: weekly or daily use. In three separate sessions, each participant smoked placebo, lower-THC and higher-THC cannabis without knowing which they had received. Women in the study were not using hormonal birth control and were tested during the same phase of their menstrual cycle. The analysis found:
- Men who used cannabis occasionally reported feeling more high, sedated and impaired than other participants, along with more unpleasant effects such as anxiety. They were also the only group whose heart rate rose significantly after smoking active cannabis.
- Women and men who used cannabis frequently responded to it in similar ways.
- Regardless of sex, people who used frequently exhibited the addictive qualities of cannabis more than those who used occasionally.
- Blood THC levels did not explain the differences. Men who used frequently tended to have the highest THC levels, yet they felt fewer effects than men who used occasionally.
“Much of what we thought we knew about sex differences in cannabis effects came from animal research and from human studies that pooled data from different trials,” said Dr. Ziva Cooper, the study’s principal investigator and director of the UCLA Center for Cannabis and Cannabinoids. “When we designed a study to look at sex and frequency of use at the same time, and controlled for hormones, the picture changed. As more women use cannabis, including for women’s health conditions, we need evidence from studies designed to include them.”
Cannabis use is rising among women, and women tend to move more quickly than men from first use to cannabis use disorder. The authors suggest women may build tolerance to cannabis with less use than men, which larger studies will need to test. The study answers the National Institutes of Health’s call for research on differences between women and men, and understanding these differences could inform how cannabis use disorder is prevented and treated.
“Sex and cannabis use history can both shape how someone experiences the effects of cannabis,” said the study’s lead author Dr. Stephanie Lake, a researcher at the UCLA Center for Cannabis and Cannabinoids. “And studying both together is key to understanding who is most at risk of higher-risk, unpleasant, or beneficial experiences from cannabis.”
The sample was modest, several findings were exploratory, and the THC strengths tested were lower than those of many products sold today. The team is now studying high-potency products and adults 55 and older, whose cannabis use is rising.
