Rationale: Little is known about the interactions between ovarian hormones across the menstrual cycle and responses to psychoactive drugs in humans. Preclinical studies suggest that ovarian hormones such as estrogen and progesterone have direct and indirect central nervous system actions, and that these hormones can influence behavioral responses to psychoactive drugs.
Objectives: In the present study, we assessed the subjective and behavioral effects of d-amphetamine (AMPH; 15 mg orally) at two hormonally distinct phases of the menstrual cycle in women.
Methods: Sixteen healthy women received AMPH or placebo capsules during the follicular and mid-luteal phases of their cycle. During the follicular phase, estrogen levels are low initially and then rise while progesterone levels remain low. During the midluteal phase, levels of both estrogen and progesterone are relatively high. Dependent measures included self-report questionnaires, physiological measures and plasma hormone levels.
Results: Although there were no baseline differences in mood during the follicular or luteal phase, the effects of AMPH were greater during the follicular phase than the luteal phase. During the follicular phase, subjects reported feeling more "High", "Energetic and Intellectually Efficient", and "Euphoric" after AMPH than during the luteal phase, and also reported liking and wanting AMPH more. Further analyses showed that during the follicular phase, but not the luteal phase, responses to AMPH were related to levels of estrogen. Higher levels of estrogen were associated with greater AMPH-induced increases in "Euphoria" and "Energy and Intellectual Efficiency". During the luteal phase, in the presence of both estrogen and progesterone, estrogen levels were not related to the effects of AMPH.
Conclusions: These findings suggest that estrogen may enhance the subjective responses to a stimulant drug in women, but that this effect may be masked in the presence of progesterone.