Cannabis research. Conceptual image of a leaf of the hemp or cannabis plant (Cannabis sativa) next to Petri dishes. Preparations of cannabis are used as illicit drugs, producing a relaxing, narcotic effect and, in higher doses, hallucinations. Cannabis may be useful medically due to its ability to relieve pain, increase appetite and control muscle spasms. The main active compounds are cannabinoids such as THC (tetrahydrocannabinol). Cannabis shows potential to treat the side-effects of chemotherapy and the symptoms of conditions including AIDS, multiple sclerosis and chronic pain from nerve damage.