For many Americans, belief can shape symptoms in real, measurable ways—even when a treatment contains no active ingredient. Psychologists and researchers say the placebo effect can improve how people feel, but it can also blur the line between evidence-based c
A pill that doesn’t contain an active ingredient can still make pain ease. A cream that isn’t medically effective can still reduce itching. In the moment, it feels like the treatment worked.
That experience has a name: the placebo effect. It’s the phenomenon where symptom improvement follows a pill or procedure that has no direct medical or biological effect on the condition being treated—driven largely by what someone expects to happen.
“It’s what happens when a person’s expectation of a response leads to a real change in their perception or physical state,” explains Jameca Woody Cooper, a psychologist and communications chair of the American Board of Professional Psychology.
The implications are personal and practical. Placebo responses can help some people feel better. but they can also create confusion. false hope. and make ineffective treatments appear legitimate. Understanding how it works. Cooper says. can help people make more informed health decisions—especially when quick answers start to crowd out a clinician’s guidance.
The placebo effect isn’t “made up.” Researchers say expectations can influence the brain and body in measurable ways.
Scientists have documented placebo responses for centuries. Cooper says. but the phenomenon gained broader recognition in the early 20th century as researchers realized patients often improved even after receiving inactive treatments. Today, researchers emphasize that placebo effects involve real biological pathways.
“Scientists now know placebo effects are not imaginary. ” says Elizabeth Hoge. a psychiatrist and director of the Anxiety Disorders Research Program at Georgetown University. Placebo responses involve real “brain pathways, neurotransmitters and hormones,” she says. In pain studies, patients have experienced genuinely reduced pain as the brain changes how pain signals are processed. Brain imaging studies. Hoge adds. show placebo responses can influence stress pathways. hormone activity. immune responses. and chemicals tied to mood and pain regulation.
That biological credibility matters beyond everyday life. Placebo effects are also central to how medical trials are designed.
Placebos are essential in clinical research because they help “researchers determine whether a product’s observed effect comes from the treatment itself or from the patient’s expectations of that treatment. ” Cooper says. Without placebo-controlled trials. it would be far harder to separate genuine medical benefits from the powerful influence of belief and perception.
Some people may be more affected than others. Scientists still don’t fully agree on why, but Cooper points to several contributing factors, including personality traits, brain chemistry, past experiences, and social context.
Traits such as “openness and optimism” appear to increase susceptibility in some cases, she adds. Emerging research, Cooper says, also suggests certain neurological conditions like attention-deficit/hyperactivity disorder may play a role.
Hoge stresses that susceptibility isn’t only about personality. The surrounding context matters too: the type of treatment being followed, the confidence of the health care provider, and the patient’s prior experiences with that treatment.
If someone previously experienced relief after taking a certain medication. she says. they may develop conditioned responses where even the routine of treatment triggers improvement. And people dealing with pain. fatigue. anxiety. and stress may be especially vulnerable. because the brain plays a central role in interpreting bodily sensations.
Even then, Hoge says susceptibility to placebo effects doesn’t mean someone is gullible or weak-minded. “If a patient has placebo effects as part of their regular medical care. it’s usually considered a good thing. ” she says. Placebo responses “can sometimes result in medical treatment working better.”.
But the same force that can support relief can also undermine clarity.
One major downside is that people may mistake temporary symptom improvement for proof that an ineffective treatment truly works. Cooper warns that people who are highly susceptible may face “a greater likelihood of being taken advantage of by questionable products or practitioners.”
Placebo responses can also complicate medical care by making it harder to tell whether a treatment is genuinely effective. For instance, someone may sincerely believe a supplement, detox, or alternative therapy helped when symptoms may have improved naturally—or because of expectation alone.
Hoge says this challenge isn’t just theoretical. While placebos are usually helpful in clinical trials, “in some kinds of research, placebo effects are so powerful, it’s hard to determine how much is due to the drug.”
There’s also a darker mirror image: the nocebo effect. Hoge explains that it occurs when patients experience side effects or worsening symptoms because they expect a problem to occur. For example. someone who believes a medication will make them nauseated may feel nauseous even if they wouldn’t have been affected otherwise.
For Cooper, the takeaway is not to deny placebo effects—it’s to use awareness strategically.
She advises people who feel especially influenced by placebo effects to “lean into it but be strategic as you do.” Her guidance is to use positive expectations to support evidence-based treatments while staying cautious about products or therapies that lack strong scientific backing.
“Use your awareness of small changes to support genuine treatments,” Cooper advises, “but protect yourself by carefully curating which products or practices you trust and avoiding anything without solid evidence.”
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