Medical cannabis (also referred to as medical marijuana) is the use of cannabis and its constituent cannabinoids such as THC as a physician-recommended form of medicine or herbal therapy. The Cannabis plant from which the cannabis drug is derived has a long history of medicinal use, with evidence dating back to 2,737 BCE.^[1]
Although the extent of the medicinal value of cannabis has been disputed, and despite the opposition to research and use put forward by most national governments, it does have several well-documented beneficial effects.^[2][3][4][5] Among these are: the amelioration of nausea and vomiting, stimulation of hunger in chemotherapy and AIDS patients, lowered intraocular eye pressure (shown to be effective for treating glaucoma), as well as general analgesic effects (pain relief).
Synthetic cannabinoids are available as prescription drugs in some countries. Examples include Marinol, available in the United States and Canada, and Cesamet, available in Canada, Mexico, the United Kingdom, and also in the United States.
There are several methods for administration of dosage, including vaporizing or smoking dried buds, drinking or eating extracts, and taking capsules. The comparable efficacy of these methods was the subject of an investigative study^[5] conducted by the National Institutes of Health.
While cannabis for recreational use is illegal in most parts of the world, its use as a medicine is legal in a number of territories, including Canada, Austria, Germany, the Netherlands, Spain, Israel, Italy, Finland, and Portugal. In the United States, federal law outlaws all cannabis use, while permission for medical cannabis varies among states. Distribution is usually done within a framework defined by local laws. Medical cannabis remains a controversial issue worldwide.

Breast cancer

According to a 2007 study at the California Pacific Medical Center Research Institute, cannabidiol (CBD) may stop breast cancer from spreading throughout the body.^[75] These researchers believe their discovery may provide a non-toxic alternative to chemotherapy while achieving the same results minus the painful and unpleasant side effects. The research team says that CBD works by blocking the activity of a gene called Id-1, which is believed to be responsible for a process called metastasis, which is the aggressive spread of cancer cells away from the original tumor site.^[75]

 HIV/AIDS

Investigators at Columbia University published clinical trial data in 2007 showing that HIV/AIDS patients who inhaled cannabis four times daily experienced substantial increases in food intake with little evidence of discomfort and no impairment of cognitive performance. They concluded that smoked marijuana has a clear medical benefit in HIV-positive patients.^[76][77] In another study in 2008, researchers at the University of California, San Diego School of Medicine found that marijuana significantly reduces HIV-related neuropathic pain when added to a patient's already-prescribed pain management regimen and may be an "effective option for pain relief" in those whose pain is not controlled with current medications. Mood disturbance, physical disability, and quality of life all improved significantly during study treatment.^[78] Despite management with opioids and other pain modifying therapies, neuropathic pain continues to reduce the quality of life and daily functioning in HIV-infected individuals. Cannabinoid receptors in the central and peripheral nervous systems have been shown to modulate pain perception. No serious adverse effects were reported, according to the study published by the American Academy of Neurology.^[79]

 Brain cancer

A study by Complutense University of Madrid found the chemicals in marijuana promotes the death of brain cancer cells by essentially helping them feed upon themselves in a process called autophagy. The research team discovered that cannabinoids such as THC had anticancer effects in mice with human brain cancer cells and in people with brain tumors. When mice with the human brain cancer cells received the THC, the tumor shrank. Using electron microscopes to analyze brain tissue taken both before and after a 26- to 30-day THC treatment regimen, the researchers found that THC eliminated cancer cells while leaving healthy cells intact.^[80] The patients did not have any toxic effects from the treatment; previous studies of THC for the treatment of cancer have also found the therapy to be well tolerated. However, the mechanisms which promote THC's tumor cell–killing action are unknown.^[