'The history of medical marijuana and its use for epilepsy is a curious one. The marijuana plant, cannabis sativa, has been a part of folk medicine since antiquity and it has been used in Western medicine since the 19th century.
One of its early uses was to control epileptic seizures. An obvious drawback, however, was that it was psychoactive -- it made its users "high." It was these psychoactive effects of cannabis that led to its being banned in most countries in the early 20th century.
In the 1930s and 1940s, research chemists began to extract various pure compounds -- called "cannabinoids" -- from the cannabis plant and discovered that some extracts made you high while others didn't.'