Randomised trial, 2025
Does open-label placebo (knowing it is placebo) help with PMS symptoms?
Yes, when women received placebo pills with a clear explanation of how placebos work, it reduced PMS symptoms compared to usual care and placebo without explanation. This shows the importance of expectation and explanation.
What they did
A three-arm randomized trial in Switzerland with 150 women aged 18-45 years with PMS or PMDD. One group received usual treatment. One received open-label placebo without explanation. One received open-label placebo with a treatment explanation. All took pills for 6 weeks. Outcomes were measured over three menstrual cycles.
What they found
At menstrual cycle 3, placebo with explanation reduced symptom intensity more than usual care (by 9.97 points, p<0.001) and more than placebo without explanation (by 6.10 points, p=0.036). It reduced symptom interference more than usual care (by 1.23 points, p=0.022) and placebo without explanation (by 1.10 points, p=0.044). 145 of 150 women (96.7%) completed the study.
What it means for you
Placebo pills work better when combined with a clear explanation of how placebos help, even when women know they are placebos. This shows explanation and expectation matter for symptom improvement. The study was rigorous and well-completed, but it is unclear how long benefits last.
150
women randomized
145 (96.7%)
women who completed the study
6 weeks
duration of treatment
About the study
- Original title
- Efficacy of open-label placebos for premenstrual syndrome: a randomised controlled trial
- Authors
- Frey Nascimento A, Gaab J, Degen B et al.
- Journal
- BMJ evidence-based medicine
- Year
- 2025
- Study design
- Randomised trial
- Participants
- 50
- What was tested
- Open-label placebo pills with or without treatment explanation for 6 weeks versus usual care
- Open access
- Yes
- Read the paper
- doi.org/10.1136/bmjebm-2024-112875
Topics
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