A look at medical history tells us there undoubtedly are some:

Such beliefs, that now seem to us so absurd that it is a wonder to us that anyone could ever have held them, were not uncommon at the time, and Freud himself, under the influence of his friend, the ear, nose and throat surgeon Wilhelm Fliess, believed that a condition of the nasal septum could cause hysterical symptoms. In the 1920s a man called Cotton tried to cure schizophrenia by taking out all the patients’ teeth, on the theory that infected teeth were the cause of the condition.

What are our theories today that will seem absurd to our successors, what unnecessary or dangerous operations performed on the flimsiest of hypotheses? We can never know. Properly conducted trials repeatedly demonstrate that widespread practices are useless at best and harmful at worst. However, there is a more fundamental principal of medical ethics than First do no harm. It is that Something must be done.