The Placebo-controlled trials are very beneficial in determining the efficiency of a product. With the Placebo trials, one group of subjects receives the real product, while the other group receives the imitation one. As a result neither group knowing which form they have, there is a less chance of a Placebo effect being present. The main issue that arises with this type of trial is giving patients with an advanced disease, the Placebo. As a result, they are given a treatment that will not benefit them at the end. On the other hand, because the subject does not know whether they are on the Placebo or not, they may feel that they are doing better mentally. With patients unaware of which type of product they received, the data collected can be analyzed to see how effective the product was.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1070847/