Placebos are often used in clinical drug trials to determine how well a potential medicine will work.

• There are two different groups of subjects in a placebo-controlled trial - one receives the experimental drug and the other the placebo. Neither researchers nor subjects know which group is receiving the real drug or the placebo.
• Some researchers are questioning the placebo-controlled trial. Not everyone thinks a drug is ineffective if the placebo performs better.
• Other critics of the placebo-controlled trial state it's wrong to attribute all positive outcomes to the placebo because many illnesses can resolve without any treatment.
• When a patient takes a placebo and experiences adverse side effects, it's called a nocebo effect. Patients taking active drugs have also been known to have side effects that can't be directly attributed to the drug.

A 2007 study revealed that 45 percent of doctors had prescribed a placebo at some point. Doctors believed that placebos had a therapeutic effect.

The most commonly prescribed placebos are aspirin, vitamins, and antibiotics. Doctors prescribe placebos because they have no other for...