Multiple Choice, Single Answer

Patients who receive a sugar pill often report feeling better, even though the pill contains no active drug. This placebo effect is strongest for symptoms such as pain and nausea, which are shaped partly by attention and expectation, and it does little to change the underlying causes of disease, such as an infection. Researchers stress that the improvement is not simply imagined: brain scans show that expecting relief can change activity in regions involved in processing pain. For this reason, clinical trials compare new drugs with placebos rather than with no treatment at all. A medicine is considered effective only if it produces clearly better results than the placebo.