, also known as marijuana or marihuana, or ganja, is a psychoactive drug extracted from the plant Cannabis sativa, or more often, Cannabis sativa subspecies, indica. The herbal form of the drug consists of dried mature flowers and subtending leaves of female plants. Hashish is the resinous from of the plant. The major biologically active chemical compound in cannabis is Δ9-tetrahydrocannabinol (delta-9-tetrahydrocannabinol), commonly referred to as THC.

Cannabis is consumed in many ways, most of which either involve inhaling smoke from a burning plant or administering orally.
Various devices exist for smoking. The most common are implements such as bongs, chillums, bowls, joints and blunts.
Vaporizers are used to inhale the THC, but not smoke.
As an alternative to smoking, cannabis may be consumed orally.
Cannabis can also be consumed as a cannabis tea. Enough THC can be dissolved to make a mildly psychoactive tea.

Cannabis has psychoactive and physiological effects when consumed. The minimum amount of THC required to have a perceptible psychoactive effect is about 10 micrograms per kilogram of body weight. The most common short-term physical and neurological effects include increased heart rate, lowered blood pressure, impairment of psychomotor coordination, concentration, and short-term memory. Long-term effects are less clear.

A synthetic form of one chemical in marijuana, Δ9-tetrahydrocannabinol (THC), is used as a treatment for a wide range of medical conditions. Clinical trials conducted by the American Marijuana Policy Project, a pro-cannabis organization, have shown the efficacy of cannabis as a treatment for cancer and AIDS patients, who often suffer from clinical depression, and from nausea and resulting weight loss due to chemotherapy and other aggressive treatments. Scientists in Italy have shown through studies that cannabidiol (CBD), a chemical found in marijuana, inhibits growth of cancer cells in animals.
In the United States, the FDA has approved marijuana as a treatment for cancer and the symptoms of HIV and Influenza. The current view of the United States Food and Drug Administration is that the consumption of isolated compounds (such as cannabinoids) is more effective than smoking or ingesting parts of the plant.
A synthetic version of the cannabinoid THC named dronabinol has been shown to relieve symptoms of anorexia and reduce agitation in elderly Alzheimer's patients. This drug is more expensive and less available than "pot" and has not been shown to be effective or safe.
Glaucoma, a condition of increased pressure within the eyeball causing gradual loss of sight, can be treated with medical marijuana to decrease this intraocular pressure. There has been debate for 25 years on the subject. Marijuana lowers IOP by acting on a cannabinoid receptor on the ciliary body called the CB receptor.
Medical marijuana is also used for analgesia, or pain relief. It is also reported to be beneficial for treating certain neurological illnesses such as epilepsy, and bipolar disorder. Case reports have found that cannabis can relieve tics in people with obsessive compulsive disorder and Tourette's syndrome. Patients treated with THC, the main psychoactive chemical found in cannabis, reported a significant decrease in both motor and vocal tics, some of 50% or more. Some decrease in obsessive-compulsive behavior was also found. A recent study has also concluded that cannabinoids found in cannabis might have the ability to prevent Alzheimer's disease. THC has been shown to reduce arterial blockages.

(2009, January 2). Cannabis (Drug). Retrieved January 5, 2009, from Wikipedia Web site:

Heather Vanportfliet
AP Psychology, 6th Hour