Marijuana Fast Facts: Highs, Lows

— Marijuana is a generic name for the sativa sub-species of Cannabis (search), which contains the highest amount of delta-9-tetrahydrocannabinol (THC), the primary psychoactive chemical in the plant. There are, however, over 400 active chemicals in marijuana. Only about 30 have been studied.

— Texts from 2,000 years ago show that marijuana was used as a medicine in a variety of ancient cultures, including China, India, Greece and Persia.

— Marijuana was legal in the United States until 1937, when it was prohibited by the Marijuana Tax Act (search). Before 1937, there were at least 27 medicines containing marijuana in the U.S. Some of the nation's biggest drug manufacturers, including Eli Lilly and Squibb (now Bristol-Myers Squibb) produced drugs from marijuana.

— Dr. William C. Woodward, chief counsel to the American Medical Association, testified on behalf of the medical groups in 1937. The AMA feared that the Marijuana Tax Act would prevent research into legitimate medical uses for it. Woodward delivered a statement that "The American Medical Association knows of no evidence that marijuana is a dangerous drug."

— Derivatives of marijuana were used as one of the primary painkillers until the introduction of commercial aspirin in 1899.

— A tincture of cannabis was used to treat Queen Victoria's menstrual cramps.

— The United States government distributes marijuana to six people in the United States who are former patients of a now-defunct medical study from the 1970s.

— All marijuana used for medical studies in the U.S. is grown at a government-backed farm at the University of Mississippi.

— Under federal law, marijuana cannot be prescribed by a doctor.

— When the Marijuana Tax Act was passed in 1937, the federal government wielded far less regulatory power than it does today and therefore imposed a "tax" on marijuana rather than prohibiting it outright. The act was worded very carefully so that the Supreme Court wouldn't overturn it for overstepping the bounds of regulating interstate commerce. The act mandated that anyone wishing to sell marijuana pay a transfer tax. Possession of marijuana without paying the tax was illegal. The required tax stamp, however, could only be issued to those already in possession of marijuana.

— Research shows that long-term marijuana use is linked to some changes in the brain similar to those seen after long-term use of other drugs like cocaine and heroin. These studies have not been corroborated.

— Long-term use of marijuana can impair cognitive functions, especially those relating to memory.

— Marijuana is the nation's No. 1 recreational illegal drug. It is No. 3 if alcohol and tobacco are included.

— There are 13 ongoing clinical medical marijuana studies and sub-studies in the United States.