If both the doctors and the participants of a scientific study know who is receiving a treatment under study and who is receiving another treatment (or no treatment at all), the procedure is called an open trial (or open study). The results have to be taken with a handful of salt: open trials are not at all reliable. In such studies, it isn't possible to determine which effects are due to the treatment itself and which are due to the
placebo effect. The main use of open trials is to look for severe adverse effects of a treatment. For this reason, they are sometimes called "drug-monitoring studies."