This article was written by Katie Fesperman, an Research Assistant at the HBPL, based on E Pabon…H de Wit (2022) Acute effects of oral delta-9-tetrahydrocannabinol (THC) on autonomic cardiac activity and their relation to subjective and anxiogenic effects. Psychophysiology.
Cannabis is one of the most commonly used drugs in the United States. However, the cardiovascular and subjective effects of ∆9-tetrahydrocannabinol (THC), the main psychoactive component in Cannabis, are not fully understood. This is especially true for women. Because females have often been excluded from studies with drugs, there are gaps in our understanding of how drugs affect women. Preclinical research (i.e., research with animals) suggests that females are more sensitive to THC, and in humans, women tend to have more adverse reactions (i.e. paranoia or anxiety) to the drug. One theory of why there are sex differences in responses to drugs is that fluctuating hormone levels across the female menstrual cycle might interact with THC, and affect drug responses in women.
The present study investigated the effects of THC administered orally in healthy female occasional Cannabis users. In order to test the interaction between hormonal fluctuations and THC, the researchers tested women during one of two phases of the menstrual cycle: the early follicular (EF) or late follicular group (LF), which are characterized by lower and higher levels of estrogen respectively. The researchers hypothesized that responses to THC would be greater in the late follicular (LF) phase compared to the early follicular (EF) phase, due to higher levels of estrogen in the LF. Women participated in an experimental study in which they attended three in-person lab visits where they took a capsule containing an inactive placebo, 7.5 mg, or 15 mg of oral THC. Throughout each session, researchers took a variety of cardiovascular (i.e.heart rate (HR), blood pressure (BP) and self-reported subjective measures (i.e. ratings of their current mood, including anxiety).
On most measures, women’s responses were similar during the EF and LF phases and estrogen levels did not strongly affect responses to THC. However, their reports of wanting more of the drug and feeling anxious occurred sooner after taking the drug in women tested during the EF phase compared to the LF phase. Why this difference on onset of effects occurred is unclear. Future research is needed to investigate how circulating ovarian hormones interact with the effects of psychoactive drugs.
Anecdotal evidence suggests that people vary markedly in their responses to Cannabis, and this variability has been confirmed in laboratory studies. However, many questions remain about the sources of individual variation in responses to THC and Cannabis. Why do some people like the drug while others don’t, why do some people feel anxious after use, whereas others feel calmer? The shifting socio-political attitudes about Cannabis use, coupled with legislative changes, makes it important to identify sources of variability in response to the drug to make it safer for use, both medicinally and recreationally.