In most studies we don’t have a “no treatment” group to compare both the placebo and the drug with, and for a very good ethical reason: if your patients are ill, you shouldn’t be leaving them untreated simply because of your own mawkish interest in the placebo effect. In fact, in most cases today it is considered wrong even to use a placebo in a trial; whenever possible you should compare your new treatment with the best preexisting, current treatment.
