Avicenna often used psychological methods to treat his patients.  One such example is when a Persian prince had melancholia, suffering from the delusion that he was a cow. He would moo and cry out, “Kill me so that a good stew may be made of my flesh,” and would never eat anything. Avicenna was persuaded to take the case. Avicenna sent a message to the patient, asking him to be happy as the butcher was coming to slaughter him, and the sick man rejoiced. When Avicenna approached the prince with a knife in his hand, he asked “where is the cow so I may kill it.” The patient then mooed like a cow to indicate where he was. The patient was laid on the ground for slaughter. When Avicenna approached the patient, pretending to be ready to slaughter him, he said, “the cow is too lean and not ready to be killed. He must be fed properly and I will kill it when it becomes healthy and fat.” The patient was then offered food which he ate eagerly, and gradually “gained strength, got rid of his delusion, and was completely cured.”

Wikipedia fragment of The Book of Healing by Persian polymath Abu Ali ibn Sīna (Avicenna)