Medical marijuana use has a history stretching back thousands of years. In prebiblical times, the plant was used as medicinal tea in China, a stress antidote in India and a pain- reliever for earaches, childbirth and more throughout Asia, the Middle East and Africa.
In recent decades, medical researchers have investigated marijuana's effects on various kinds of pain -- from damaged nerves in people with HIV, diabetes and spinal cord injury; from cancer; and from multiple sclerosis. Marijuana has also been hypothesized to help with nausea induced by chemotherapy and antiretroviral therapy, and with severe loss of appetite as seen in people with the AIDS wasting syndrome.
The weed's actions are due to the active ingredients tetrahydrocannabinol (THC) and some 60 other cannabinoids, which mimic the action of chemicals -- known as endogenous cannabinoids -- that exist naturally in the brain. Those cannabinoids activate receptors in our nerves, triggering physiological responses.
A legal prescription form of THC (Marinol) exists, yet researchers say it's far from a perfect drug. Taken orally, its absorption is highly variable and unpredictable and often delayed, says Dr. Igor Grant, a UC San Diego psychiatrist who directs the university's Center for Medicinal Cannabis Research. "Smoking is a very efficient way to deliver THC," he says.
As a result of its federally illegal status, medicinal use of marijuana is restricted to carefully vetted clinical research studies or to patients in states such as California that have passed laws to allow for personal medical use. Research on the medicinal use of marijuana relies on government-issued marijuana cigarettes, which come in different strengths and are supplied by the National Institute on Drug Abuse.
The UC Center for Medicinal Cannabis Research in San Diego helps coordinate clinical studies to investigate the safety and effectiveness of marijuana. Here's what they've found.
Neuropathic pain
Recent research suggests that marijuana can assuage this chronic-pain syndrome in which burning sensations occur and simple touch can feel like hurt. It is unaffected by aspirin-like drugs and fairly resistant to stronger analgesics such as opiates.
