There is evidence that cannabis has been used for over 12,000 years; there are texts from as far back as 2737B.C. which list the medicinal uses of cannabis.
THC and other cannabinoids' have been shown to have analgesic, anti-spasmodic, anti-convulsant, anti-tremor, anti-psychotic, anti-inflammatory, anti-emetic and appetite-stimulant properties. Research is ongoing into the Neuro protective and immunomodulatory effects of cannabis.
Nearly all medicines have toxic, potentially lethal effects; however there is no credible medical report to suggest that consuming marijuana has caused a single death in fact estimates indicate that a person would have to consume 20,000 to 40,000 times as much cannabis as is contained in one cannabis cigarette, and they would have to consume this amount in a short space of time (e.g. less than 1 hour).