The placebo and nocebo effects: the power of expectation

In short: A placebo effect occurs when someone feels better after a treatment with no active ingredient, such as a sugar pill. With the nocebo effect, expectation conversely leads to complaints or side effects.

In more detail: Both effects are driven mainly by expectations, previous experiences and the treatment setting. They work especially on subjectively experienced symptoms such as pain, nausea or fatigue, but they do not cure diseases such as infections or tumours.

In detail

• Expectation: People who expect improvement often perceive symptoms as weaker; measurable changes can be observed in the brain, for example in pain processing.
• Learning from experience: Someone who has often found that a tablet helps will also respond to a similar pill without an active ingredient (klassische-und-operante-konditionierung).
• The setting matters: Attention, time and a trusting conversation with a doctor can improve how people feel.
• Nocebo in everyday life: People who read the package leaflet and fear side effects sometimes notice exactly those, even with preparations containing no active ingredient.
• Importance for research: This is why new medicines are tested in studies with placebo groups and, where possible, double-blind, so that neither participants nor practitioners know who is in which group.
• Open-label placebos: In some studies placebos helped even when participants knew they were receiving a dummy pill; the findings are interesting but still limited.
• Limits: A placebo effect is no proof that a method works; many alternative treatments do no better than placebo in good studies (kognitive-verzerrungen).
• Important note: Never stop taking prescribed medication on your own; questions about effects and side effects belong with your doctor or pharmacist.