Marijuana comes from the cannabis plant. The main psychoactive ingredient in marijuana is THC (delta-9-tetrahydrocannabinol) which is a type of cannabinoid. Cannabinoids are chemicals that act on certain receptors on cells in our body, especially cells in the central nervous system.
Some people believe that marijuana can help control or relieve some of the symptoms of cancer or the side effects of cancer treatments. Some people find relief from smoking; others from the oil. Research does show that some cannabinoids can help with some symptoms and side effects, and drugs containing cannabinoids have been developed to treat pain, neuropathic pain (pain caused by damaged nerves), anorexia or cachexia, and nausea and vomiting.