The conventional wisdom about placebos has held for decades: they only work if the patient doesn’t know. Deception, the thinking goes, is essential to the effect.
A study published March 21 in the International Journal of Clinical and Health Psychology challenges that assumption with data from 90 healthy older adults. Researchers at Universita Cattolica del Sacro Cuore in Milan found that open-label placebos, pills that patients were explicitly told were inert, produced cognitive and physical improvements comparable to deceptive placebos and, on some measures, exceeded them.
After three weeks, the open-label group showed memory improvements of 6.9 to 21.5 percent and a 9.2 percent increase in physical performance. The effects were similar to those seen in the deceptive placebo group, and comparable to some experimental studies of actual cognitive and physical training.
The team, led by Francesco Pagnini (Professor of Clinical Psychology), designed a randomized controlled trial with three arms. One group received deceptive placebos, told the pills were active dietary supplements. A second group received open-label placebos, told explicitly that the pills lacked any active ingredient but could still trigger mind-body responses. A third served as a no-treatment control.
All participants were healthy, community-dwelling older adults. The intervention lasted three weeks, and the researchers measured a battery of outcomes including perceived stress, psychological well-being, sleepiness, fatigue, optimism, self-efficacy, aging stereotypes, short-term memory, selective attention, and physical performance.
The results were unambiguous. Both placebo groups outperformed the control on cognitive and physical measures. But the open-label group had an edge on one key measure: perceived stress reduction was most pronounced in the open-label condition, significantly lower than both the deceptive placebo group and the control.
“These are significant effects,” Pagnini said, “comparable to those seen in some experimental studies on physical activity regarding physical performance and cognitive training, especially with regard to memory.”
The Ethics of Deception
The finding matters because it removes the ethical problem at the heart of placebo use. Deceptive placebos require lying to patients, which is why they have limited clinical application outside of controlled trials. Open-label placebos, by contrast, can be prescribed transparently.
The study does not claim to explain the mechanism. The open-label placebo effect likely involves multiple psychological pathways: expectation, conditioning, the therapeutic ritual of taking a pill, and perhaps the patient’s own active engagement with their health. The participants knew the pills were inert, but they also knew they were part of a study and had chosen to participate, a context that itself may trigger beneficial responses.
“Placebo mechanisms in aging,” the authors write, “can be harnessed without deception.”
The study was funded through Italy’s PNRR (National Recovery and Resilience Plan) grants under the Age-IT project, which supports research on healthy aging.
Limitations
The sample was relatively small (90 participants) and limited to healthy older adults who volunteered for a placebo study, a self-selected group that may be particularly open to mind-body interventions. The three-week duration does not address whether the effects persist or fade with longer use. And the study did not include an active-treatment comparison, so the placebo effects cannot be directly compared against pharmaceutical or exercise-based interventions in the same population.
Still, the results add to a growing body of evidence, including similar studies in chronic pain, irritable bowel syndrome, and depression, that the placebo effect does not require concealment.
Pagnini and his co-authors, Diletta Barbiani and Alessandro Antonietti, plan to investigate whether the effects can be sustained over longer periods and whether the approach can be combined with actual interventions for additive benefits.
Source: Barbiani D, Antonietti A, Pagnini F. “Placebo mechanisms in aging: A randomized controlled trial comparing deceptive and open-label placebos on psychological, cognitive, and physical functioning in older adults.” International Journal of Clinical and Health Psychology 2026; 26(1):100673. DOI: 10.1016/j.ijchp.2026.100673