With the proposed study, the investigators aim to evaluate the long-term efficacy of the open-label placebo (OLP) intervention in premenstrual syndrome (PMS) and to contribute to a broader understanding of how OLPs work. It is planned to survey participants of the intervention groups (OLP+ and OLP-) regarding symptom intensity and impairment due to PMS after the conclusion of our randomized controlled trial (RCT) and intervention provision. Additionally, it will be examined if there is a difference between the OLP group with and without a treatment rationale (OPL+ vs. OLP-) across time. More precisely, it will be investigated whether participants of the intervention groups with and without treatment rationale experience any long-term improvement.

Inclusion Criteria:

• Participants are willing to participate in the follow-up study
• Participants have the ability to use an electronic device with internet access to complete the online follow-up survey
• Participants give Informed consent
• Participants have a regular menstruation (i.e., no menopause; pregnancy; cycle inhibiting medication etc.)

Exclusion Criteria:

• Pregnancy or breastfeeding (currently or within the last three months)
• A severe psychological or somatic disease, affecting premenstrual complaints (e.g., cancer of the uterus or fallopian tubes)
• Commencement of the menopause, sterilization, or (part) resection of the uterus or fallopian tubes
• Changes in body mass index (i.e., under 18 or above 30)

95 women who participated in the intervention groups of the RCT OPEN-LABEL PLACEBO TREATMENT OF WOMEN WITH PREMENSTRUAL SYNDROME: A RANDOMIZED CONTROLLED TRIAL (OLPPMS_1, SNCTP000002809, NCT03547661) and completed study participation (OLP+: N=48 and OLP-: N=47).