Placebo mechanisms in aging: A randomized controlled trial comparing deceptive and open-label placebos on psychological, cognitive, and physical functioning in older adults

No study has yet examined whether a placebo in its traditional meaning—an inert treatment presented as active—can influence functions that tend to naturally decline with age. We aimed to clarify whether a deceptive and open-label placebo procedure would affect psychological, cognitive, and physical functioning in community-dwelling older adults. Ninety healthy older adults were randomly assigned to one of three conditions: a control group receiving no intervention; a deceptive placebo group receiving placebo pills along with information that these contained active ingredients known to improve functioning and well-being; an open-label placebo group, explicitly informed that the pills were inert but capable of eliciting beneficial mind–body responses. Participants completed self-report measures (perceived stress, psychological well-being, sleepiness, fatigue, optimism, self-efficacy, aging stereotypes) and objective tests of short-term memory, selective attention, and physical performance before and after the 3-week intervention. After 3 weeks, the open-label placebo group exhibited lower perceived stress compared with both the deceptive placebo and control groups. Short-term memory performance also significantly improved in the open-label placebo group relative to controls. Within-group analyses revealed consistent cognitive and physical improvements in both placebo groups, with particularly pronounced effects in the open-label placebo group. Placebo interventions enhanced multiple domains of functioning in older adults, with open-label placebos producing benefits comparable to or greater than deceptive placebos. These findings suggest the potential of open-label placebos as a promising, ethically acceptable approach for supporting healthy aging.