Placebo and sham treatment are methods used in medical trials to help researchers determine the effectiveness of a drug or treatment. Placebos are inactive substances used to compare results with active substances. And in sham treatments, the doctor goes through the motions without actually performing the treatment.

A placebo is often used in a drug trial to help show whether the drug being studied is more effective than an inactive "sugar pill." Some of the people in the drug trial get the active drug while others get the inactive placebo. The results of each group are compared.

In a sham treatment, some people get the real treatment while others get the sham treatment. Then the results are compared.

When a person who is taking the inactive substance or who has had a sham treatment reports that symptoms have improved, this improvement is called the placebo effect. It is probably a result of the brain releasing "feel-good" hormones such as endorphins in response to treatment. Active drugs and therapies can also have a placebo effect. It can be difficult for researchers or doctors to know if the reason a drug works is because of its active ingredient or because of the placebo effect.

Regulations govern studies that use placebos or sham treatments. These studies are always done with the participants' consent.