There has never been a recorded death due to overdosing on cannabis. In fact, in states that legalized medical marijuana for pain relief, overdoses due to prescription narcotics like Vicodin and OxyContin have been shown to drop by as much as 25%. Marijuana is not only safer than currently available prescription narcotics, but it is also safer than publicly available substances like alcohol or cigarettes.
Use of THC-heavy strains of cannabis can result in a high that affects perception and reflex, so patients should take precautions similar to prescription-strength painkillers or alcohol. Do not drive or operate heavy machinery while taking high-THC strains of medical cannabis.