Proven for: Chronic neuropathic pain
Credit: Mark Rose / Getty Images

Of all the different health issues that are treated with medical marijuana, this one has the most scientific support. It's good news, because neuropathic pain affects people with a variety of diseases – like diabetes and multiple sclerosis – and physical trauma. Studies from the Center for Medicinal Cannabis Research, where Dr. Atkinson works, have found that pot can reduce a patient's reported pain intensity by about 34 to 40 percent (versus 17 to 20 percent with a placebo). What's more, the marijuana they use contains only about 1 percent to 8 percent of the psychoactive compound THC, whereas street versions of the drug often contain in the vicinity of 13 percent.