Men and women experienced largely similar acute effects after smoking marijuana across THC potencies ranging from 6.25% to 22%, according to a new placebo-controlled study published in Psychopharmacology.
Researchers with the Centre for Addiction and Mental Health and University of Toronto examined 35 adults, including 18 females and 17 males, who reported using marijuana one to five days per week. Each participant completed sessions involving placebo marijuana and products containing 6.25%, 12.5% and 22% THC, equivalent to approximately 0, 47, 94 and 165 milligrams of THC per cigarette.
The study used a randomized, double-blind, placebo-controlled, within-subject design, allowing researchers to compare physiological effects, blood and oral-fluid cannabinoid concentrations, subjective effects, mood and cognitive performance after each potency.
Females and males smoked similar amounts of marijuana and reached similar concentrations of THC and its metabolites in their blood. However, females spent significantly more time smoking and had significantly lower THC concentrations in oral fluid.
Researchers said the oral-fluid finding could have implications for roadside marijuana testing because THC detected in saliva is largely deposited in the mouth during smoking. Differences in smoking patterns and other physiological factors could therefore influence oral-fluid THC levels even when blood THC concentrations are similar.
Some additional differences were detected. Females showed a faster onset for certain subjective effects and smaller increases in blood pressure in some comparisons. However, researchers found little consistent evidence that sex substantially changed how participants experienced marijuana, including measures of feeling high, mood, cognition and the relationship between blood THC levels and reported effects.
The authors said the research is, to their knowledge, the first placebo-controlled human laboratory study to examine sex differences across such a broad range of smoked marijuana potencies reaching 22% THC.
The findings are notable because much previous laboratory research has used marijuana containing less than 6% THC, substantially below the potency of many products currently available to consumers.
Researchers cautioned that the relatively small sample size meant the study was primarily capable of detecting moderate-to-large differences. The participants were also mostly young adults who regularly used marijuana, and the researchers did not control for menstrual cycle phase, limiting how broadly the findings can be applied.
Overall, the researchers concluded that there was minimal evidence of consistent sex differences in the acute effects of smoked marijuana across the potencies tested, while calling for larger studies examining factors such as hormones and other sources of variation within each sex.
