Abstract
Background: This study examined effects of oral delta-9-tetrahydrocannabinol (THC) in women at two phases of the menstrual cycle differing in circulating levels of estrogen (E). Pre-clinical findings indicate that E increases sensitivity to THC and other cannabinoids, raising the possibility that higher E may be a risk factor for adverse responses to THC in women. Methods: We examined subjective and behavioral responses to THC (7.5 and 15 mg oral) and placebo in women during the early follicular (EF) phase when E levels are low and the late follicular (LF) phase when E levels are higher. Outcome measures included self-report ratings of drug effects, cardiovascular measures, and biochemical verification of ovarian hormone levels. We hypothesized that women would exhibit greater responses to THC during the LF phase compared to the EF phase. Results: On most measures, responses to THC were similar during the two phases. However, on two self-report measures, "Wanting More" drug and anxiety, the effects occurred slightly earlier after drug administration in women who were tested during the EF phase. Conclusions: We conclude that the differences in levels of E occurring during the early and LF phase of the menstrual cycle do not strongly influence responses to THC. It remains to be determined whether responses are similarly stable across other cycle phases, or in women receiving exogenous hormone treatments.