Microdosing LSD in Women With Premenstrual Disorders

Inclusion crtieria: * Between 18-45 years. * Are menstruating and have cycles with a duration between 21 - 35 days. * Meet DSM-V criteria for PMDD or criteria for severe PMS with daily ratings over 2 cycles to confirm luteal symptoms. 1. For PMDD, participants must have a minimal average luteal phase score of mild (≥3 on a 6-point scale) for at least 5 Symptoms on the DRSP including 1 mood symptom during the 5 most symptomatic of the final 7 luteal phase days and the first 2 days of menses onset, and the average follicular phase score must not be \>2 on these same items. 2. For severe PMS, participants must have a minimal average luteal phase score of mild (≥3 on a 6-point scale) for at least 4 Symptoms on the DRSP including 1 mood symptom, during the 5 most symptomatic of the final 7 luteal phase days and the first 2 days of menses onset, and the average follicular phase core must not be \>2 on these same items. * Have reported PMDD/PMS symptoms for the majority of menstrual cycles (\>9 of 12) during the year prior to screening. * Sufficient understanding of the German language * Sufficient understanding of the study procedures and risks associated with the study. * Participants must be willing to adhere to the study procedures and sign the consent form. * Willing not to drive or operate heavy machinery during the acute treatment phases of the study. * Willing to refrain from more than 7 standard alcoholic drinks a week, more than 10 cigarettes a day, and any illicit substances. * Willing to use effective contraceptive measures throughout study participation. Exclusion Criteria: * Known hypersensitivity to LSD * Current treatment for PMS/PMDD * Use of an oral hormonal contraceptive \< 6 months. * Past or present bipolar or psychotic disorder, including depressive disorder with psychotic features. * First degree relative with a psychotic disorder. * Significant prodromal psychotic symptoms (Prodromal Questionnaire-16 symptoms ≥ 6). * Borderline personality disorder. * Current post-traumatic stress disorder. * Pregnant or breastfeeding * Planned pregnancy. * Current or recent history of significant suicide ideation or suicide behavior within the past 6 months. * Current substance use disorder (\< 12 months) other than tobacco smoking. * Other illness that excludes repeated LSD administration or requires interfering medication. * Participation in another clinical trial (currently or within the last 30 days)