Allopregnanolone and Dynamic GABA-A Receptor Plasticity in Selective Serotonin Reuptake Inhibitor Responsive Premenstrual Dysphoric Disorder

This study is investigating how a naturally occurring hormone called allopregnanolone (which fluctuates with the menstrual cycle) affects GABA receptors in the brain — and how this relates to premenstrual dysphoric disorder (PMDD), a severe form of PMS that causes significant mood and emotional symptoms before each period. **You may be eligible if...** - You are a woman between 18 and 50 years old - You have regular menstrual cycles (24–35 days) - You are fluent in English - You are able to give written consent **You may NOT be eligible if...** - You have taken any psychiatric medications in the past 2 months - You have a substance use disorder in the past 6 months - You have a history of a psychotic disorder, bipolar disorder, or major depression with psychosis - You use hormonal contraceptives or other steroid hormones - You have been pregnant in the past 6 months - You have a history of seizures, severe liver problems, or a heart rhythm condition Talk to your doctor to see if this trial is right for you.