1. Open-label placebos given with treatment rationale significantly alleviated symptoms of premenstrual syndrome in women aged 18 to 45 years with moderate to severe PMS or premenstrual dysphoric disorder.
2. The study involved 150 participants and found that the group receiving placebo had lower symptom intensity and interference compared to the other groups. 
3. The intervention consisted of two placebo pills daily for 6 weeks, with high adherence (93.18%) and minimal side effects (four non-serious adverse events reported). 
4. Placebos have the potential to be an ethical, non-pharmacological intervention for PMS, especially for patients seeking alternatives to standard treatments with undesirable side effects. 

Source: BMJ Evidence-Based Medicine