Other scientists who study placebos called the study fascinating and said they are hopeful that it will stimulate further research, but cautioned that much more needs to be considered before this work could be extrapolated to clinical settings. For example, the study only observed a very short-term response among the subjects. Although EEG is a reliable approach to measure early brain responses, Miller says, seeing an effect for the first few seconds of an emotional response in healthy people makes it hard to interpret what that could mean for treating a long-term psychiatric condition. “I see no way you can make any inferences from that kind of short-term outcome,” he says.
For that reason, Tor Wager, a professor of neuroscience at Dartmouth College and a co-author of the study, says it will be important to track changes in the long run. “We need to know something about which placebo effects last a long time, which ones fundamentally change something in your brain,” he says. He suspects that different “ingredients”—like reinforcing belief in the effectiveness of the placebo at a particular time—could make placebos more or less durable. Ultimately, he says, the way to discern this would be to track whether non-deceptive placebos implemented through different strategies really affect a person’s long-term behavior and decision-making in a way that contributes to their life.
It will also be important to observe the response in different brains areas using functional MRI, says Fabrizio Benedetti, a professor of neuroscience at the University of Turin. EEG gives readings of the whole brain, but looking more granularly at the brain using fMRI “allows us to identify specific regions involved in a given effect,” Benedetti wrote in an email to WIRED.
Additionally, Guevarra’s subjects did not include people with diagnosed mental health conditions. Would the effect he observed look the same in clinical populations as it does in a healthy one? It’s hard to say. In her own work, Colloca has found that the placebo effect is identical in healthy participants and chronic pain patients. But mental health conditions may be more complex to address, which makes her suspect that these findings may be harder to replicate. The placebo effect may be influenced by “the way we perceive context around us and [how] learning experiences shape our own vision in conditions like major depression, anxiety, generalized anxiety or schizophrenia,” says Colloca. “I think that is an area that we didn’t thoroughly explore yet and may be fascinating.”
As with any other possible intervention, non-deceptive placebos would have a lot of obstacles to overcome should they make it from lab to clinic. The effects would have to be shown to work in a larger, more diverse population, especially since the placebo effect itself has been shown to be different across people of different races, ages, and genders. And as Colloca points out, practitioners in fields such as psychology and pain management are not at the stage of prescribing non-deceptive placebos. “You can’t go to the pharmacy and say to your physician, ‘I want a placebo’. We are not there yet,” she says.
In fact, some scientists raise ethical caveats about the use of placebos in clinical research. Benedetti worries it may fuel pseudoscience, and could increase what he calls “pseudotreatments.” In a commentary published last year, he wrote that because scientists have shown how powerful expectation can be, people may be led to believe that anything—be it talismans, bizarre rituals, or even water—can be used to boost expectations and trigger the brain mechanisms that control the placebo effect.
Benedetti argues that there must be careful considerations about whether or not to bring non-deceptive placebos into the clinic. If they are, he says, the science cannot be oversold and has to be presented carefully. Not all conditions respond to the placebo effect, and people should not avoid necessary treatment, Benedetti points out. “The psychological component of some illnesses can indeed be modulated by placebos, but placebos cannot stop cancer growth nor can they kill the bacteria of pneumonia,” he wrote by email.