Placebo pills can have real effects through the power of suggestion
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Women with premenstrual syndrome seem to benefit from the placebo effect even when they know they are taking sham pills, suggesting this could provide a cheap and easy treatment.
Premenstrual syndrome (PMS), which involves symptoms such as anxiety, mood swings and abdominal cramps, commonly affects anyone who has periods. Previous studies have found that placebo pills can reduce symptoms in women who think they may be taking a real medication, but it was unclear whether these benefits remain when people knowingly take sham pills.
Antje Frey Nascimento at the University of Basel in Switzerland and her colleagues recruited 150 women in Switzerland aged 18 to 45 who had moderate to severe PMS. In a survey that scored 27 PMS symptoms on a scale of 0 to 5, the participants rated at least one symptom a 4 or a 5 at the start of the study. The participants also reported that at least one symptom interfered with their social, work or school lives, scoring this disruption a 4 or a 5.
Next, the researchers randomly assigned one-third of the participants to take two placebo pills daily over two menstrual cycles, and told these people they were taking placebos. Another third of the participants also took placebo pills, but they received an additional explanation of how placebos can relieve symptoms through the power of suggestion and belief.
The remaining third of participants were not given placebos, but all groups were able to take their normal medications. All the participants completed daily surveys on their PMS symptoms and how much these interfered with their lives.
By analysing survey data from the participants’ final menstrual cycle, the team found that those who took placebos without an explanation saw a 50 per cent reduction, on average, in the intensity of their PMS symptoms, compared with what they reported before they took the pills. These symptoms were also half as disruptive to their lives.
Those who took a placebo with an explanation reported an even greater reduction of 79 per cent in the intensity of their symptoms and 83 per cent less disruption to their lives. “That is a really substantial effect that you will notice in your life,” says Stefan Schmidt at the University of Freiburg in Germany, who wasn’t involved in the study.
When people take placebo pills, they may both subconsciously and consciously expect symptom relief from the placebo effect; this seems to generate real improvements – for instance, by causing the release of natural painkillers in the body like endorphins, says Schmidt.
“We are living in a pill society where there is all this knowledge about how, when you ingest them, you get all the benefits of science in your body, so people expect to feel better,” he says. Highlighting these potential benefits to people seems to enhance the effect, he says.
Despite not taking any pills, the control group saw a smaller 33 per cent reduction in the intensity of their symptoms and found they were 46 per cent less disruptive than before. “Enrolling in a study and completing these daily diaries may make you feel better or pay more notice to when symptoms get better, so they see benefits even without taking any pills,” says Schmidt.
One limitation of the study is that those who signed up for the trial may be more open to alternative treatments than the wider population, and therefore see greater benefits of the placebo effect, he adds.
Larger studies should determine whether these benefits of placebos last over longer periods and whether they apply to a broader range of people in older age groups or other countries, says Schmidt. If the results stand up to scrutiny, placebos could eventually offer a cheap and easy way to treat a significant health burden, he says.
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