The preparation of these active materials represented a prodigious amount of work on the part of the chemists, but for some strange reason practically all work on the drug has now been abandoned. We have no idea what happens to this potent substance, tetrahydrocannibinol, after it enters the body. We cannot tell in what form it enters the brain or in what manner it affects the chemistry of the brain cells. Despite the tremendous recent interest in psychochemistry this important group of compounds has been ignored and we know as little about the mode of action of the hemp drug on the brain as did Hasan-i-Sabbah when he fed it to his followers a thousand years ago.

Robert S. De Ropp, Drugs and the Mind, 1957