Open-Label Placebo Treatment of Women With Premenstrual Syndrome: A Randomized Controlled Trial

Recent evidence suggests that in certain clinical conditions - such as chronic low-back pain, migraine, irritable bowel syndrome, attention deficit hyperactivity disorder, and rhinitis - placebos improve clinical outcomes even without deception. Premenstrual syndrome (PMS) is defined as clinically significant symptoms, comprising at least one emotional or physical symptom in the premenstrual phase of the menstrual cycle and which cause substantial distress or functional impairment. To date, there exists no study examining open-label placebo responses on PMS. However, PMS seems to be considerably susceptible to placebo effects: The Royal College of Obstetricians and Gynaecologists alerts to substantial placebo responses in randomized-controlled PMS trials and studies showed considerable placebo effects on PMS without any specific effect for the medication under examination. Furthermore, a myriad of distinctive therapies is described for PMS (including pharmacological and phytopharmaceutical drugs as well as complementary non-pharmacological interventions), yet partially mixed evidence is reported. Besides being considered as placebogenic, PMS symptoms are timely well-defined and delimited which further makes this condition attractive for an investigation of open-label placebo responses, as a possible amelioration can be measured in a delimited time frame. To sum up, a randomized controlled trial of an open-label placebo treatment of women with PMS allows to investigate ways to harness placebo effects ethically in clinical practice for syndromes with somatic and psychologically described characteristics.