Placebo controlled trials are a great way of helping scientists understand why a new medical treatment is more useful and effective than no treatment at all. Due to the “Placebo effect”, some patients may progress and get better without receiving any treatment at all, therefore lowering the accuracy of these trials. Nevertheless, because of this affect, researchers have seen that many patients improve due to psychological reasons without receiving any treatment. As a method of determining if a new drug or treatment is safe and effective, researchers compare the results to that of the impact of the Placebo of that treatment. This helps professionals collect data on new types of therapies and its effectiveness in treating specific medical conditions. For safety reasons, Placebos are not used in trials where patients have life threatening illnesses or if a established cure or treatment already exists. At times, the FDA may request the use of a placebo to prove that a new drug or treatment is safe and effective. In all clinical trials, volunteers who receive a placebo get the same attention, care and monitoring as those who have received an actual drug or treatment. Placebos offer a very direct approach in studying new medicines.

References:
http://hsro.med.miami.edu/documents/What_is_a_Placebo_Controlled_Clinical_Trial.pdf