Actually, nothing. From the middle of the XIII century they began to be kept in separate shelters, later in hospitals. But they could only be called hospitals relatively: patients were shown there for money to the public, like in a zoo. They were not treated, but simply fed, provided shelter and pacified by all means: cold water, beating, tying chains, bloodletting (well, they were then treated for everything). Only in the 1770s. first in Italy (Florence, Naples), and then in revolutionary France (1790s) and America, the individual reformers Chiarugi, Pinel, Dix "removed the shackles" from patients, began to use opium and other sedatives instead of chains and sticks, introduced hygienic rules and turned public opinion towards the recognition of mentally ill people. They were "treated" mainly with primitive manual labor and sedatives.
In the 19th century there was a kind of explosion of inventions and technologies: mentally ill people were spun on centrifuges, treated with vomiting and hair pulling, innovative ointments. Further - more: with the development of medicine, viral and bacterial theories of mental illness appeared, connections between mental and organic diseases (syphilis) were revealed, and they began to be treated in the same way as organic lesions were treated - by surgery (removal of foci of inflammation), mercury, arsenic, iodine. Then they beat me with electricity. Only in the middle of the 19th century did the actual classification of mental illnesses appear, where they began to differ in types, and not according to the alleged sources, as before. But in any case, before antipsychotics, it was a palliative treatment with a constant feeling for the connection between the psyche and organics and the lack of its evidence. At the turn of the XIX-XX centuries, psychoanalysis began to conquer the world, and in general everything was mixed, so that only after the 2nd World War it became modern psychiatry.
Previously, shock methods were used: insulin-shock, atropinomatous and electroconvulsive. Insulin shock is the administration of large doses of insulin up to hypoglycemic coma. Atropinomatous - this is the introduction of large doses of atropine until a deep suppression of consciousness or its shutdown, i.e. to atropine coma.
Well, or with the help of a current, so to speak, they caused an epileptic seizure, which had a "healing" effect.
These methods were most often used to interrupt psychosis.
They also used cooling, when the patient was tied up and doused with cold water, or wrapped in a cold wet sheet.
Oh, yes, there is also a well-known lobotomy, although they tried with it " treat "not only schizophrenia.