Trepanation was practiced as early as 10,000 B.C but was revived in the 18th century. Trepanation was the process in which a hole was drilled into the top of the head. The hole was believed to release evil elements that cause madness.
It was also viewed as posession. and was treated by exorcisms.
Not all ancient scholars agreed with this theory though.
The Greek physician Hippocrates believed that all illnesses, including mental illnesses, had natural origins.