Placebos in clinical trials: what it means for you

What a placebo is

A placebo looks like the study treatment but has no active ingredient, such as a sugar pill or a saltwater injection.

Comparing a treatment with a placebo helps researchers tell whether improvements come from the treatment itself or from other things, like the extra attention of being in a study.

When placebos are used

Placebos are used mainly when there is no proven treatment for the condition, or when the study treatment is added on top of your regular care.

Ethics boards generally don't allow a placebo in place of an effective treatment when going without it could cause serious harm. Trials for serious illnesses rarely give a placebo alone instead of treatment.

Standard-of-care comparisons

Many trials compare a new treatment with the current standard of care instead of a placebo.

In these studies, everyone gets either the new treatment or the best treatment already available. Some studies give everyone standard care and add either the new treatment or a placebo on top.

Will you know what you're getting?

In many trials you won't know whether you're getting the study treatment or a placebo until the study ends, and some participants are only told after all results are analysed.

Ask whether you'll be told afterwards. This is called blinding, and it keeps expectations from affecting results. In an emergency, the study team can find out which treatment you received.

Your chances of getting a placebo

The consent form tells you whether the study uses a placebo and the chance of being placed in that group. Some studies are set up so more participants get the study treatment than the placebo, and some offer the study treatment to everyone after an initial period.

Questions to ask

Does this study use a placebo? What are my chances of getting it? Will I keep my current treatment? What happens if my condition gets worse? Can I get the study treatment after the study ends?

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Quick answers

What is a placebo in a clinical trial?

A placebo looks like the study treatment but has no active ingredient, such as a sugar pill or a saltwater injection.

When do clinical trials use placebos?

Placebos are used mainly when there is no proven treatment for the condition, or when the study treatment is added on top of your regular care.

Do all trials use placebos?

Many trials compare a new treatment with the current standard of care instead of a placebo.

Will I know if I'm getting a placebo?

In many trials you won't know whether you're getting the study treatment or a placebo until the study ends, and some participants are only told after all results are analysed.

Sources

• World Medical Association — Declaration of Helsinki
• NIH — Clinical Research Trials and You: The Basics
• ClinicalTrials.gov — Learn About Studies