Participants delegated to the "control" arm will be individuals without premenstrual symptoms in the luteal phase of the menstrual cycle. Participants will be asked to track mood across the menstrual cycle, answer self-report surveys, and complete four blood draws.

Participants delegated to the "PMDD with sertraline" arm will be individuals with severe premenstrual symptoms in the luteal phase of the menstrual cycle. Participants will be asked to track mood across two menstrual cycles, answer self-report surveys, and complete eight blood draws (four in each menstrual cycle). In the second cycle, participants in this arm will take a daily pill of 50 mg of sertraline from ovulation until menses onset (end of menstrual cycle 2).

Participants delegated to the "PMDD with placebo" arm will be individuals with severe premenstrual symptoms in the luteal phase of the menstrual cycle. Participants will be asked to track mood across two menstrual cycles, answer self-report surveys, and complete eight blood draws (four in each menstrual cycle). In the second cycle, participants in this arm will take a daily placebo pill from ovulation until menses onset (end of menstrual cycle 2).

The intervention will be in the form of an oral pill, taken daily, from the day of positive urine ovulation test result until the day of menses onset.

The primary outcome variable is levels of neuroactive steroids in blood; from the early luteal phase (2 days post ovulation) compared to the late luteal phase (days 5 to 1 prior to predicted menses onset)

Neurosteroidogenic enzyme expression levels will be measured in the early luteal phase (2 days post ovulation) and the late luteal phase (days 5 to 1 prior to predicted menses onset). Levels will be compared between the healthy controls and PMDD groups at cycle 1, and between sertraline and placebo groups at cycle 2, respectively; between cycle 1 (first menstrual cycle when blood draws will be completed) and until the end of the participants' time on the study (2-3 months).