Under the DSM-5, Premenstrual Dysphoric Disorder (PMDD) is classified as a depressive disorder. Diagnosis requires at least five symptoms to be present during the late luteal phase (the week before menses), which must improve within a few days after menses onset and become minimal or absent in the follicular phase (the week post-menses). At least one symptom must be a core mood symptom (e.g., affective lability, irritability, depressed mood, or anxiety). To confirm diagnosis, these symptoms must cause significant distress or impairment, occur in the majority of cycles over the past year, and be prospectively tracked and rated daily for at least two consecutive menstrual cycles. Differential diagnosis is critical, as premenstrual exacerbation of pre-existing psychiatric conditions can mimic or complicate PMDD measurement.