The ethics of clinical placebo controlled studies have been and are intensively examined from both sides.

It would be extremely unethical to control a study on childhood leukaemia with a placebo when we know that no treament is far worse than the best treatment that is available. In these cases, a new treatment will be compared against an existing successful treatment. It is important to notice that not just any new treatment is tested this way. The new treatment must be shown to have relevant activity in terms of the mechanism of action and have proven activity at the molecular, cellular and whole organism level.

These thought modes did not just spring up overnight, they are the result of many mistakes which were made in the early history of medicine.

The other side of the problem is the question: is it ethical to treat people when you cannot prove if the treatment is successful?