Medical Marijuana Marijuana has been used as a medicine for thousands of years in ancient China, Egypt, India, Greece, and other countries. By 2014 more than 20 states had legalized medical marijuana, with similar legislation pending in other states. Recreational use for adults is legal in two states, Colorado and Washington. Marijuana can relieve certain types of chronic pain, inflammation, muscle spasms, nausea, vomiting, and other symptoms caused by such illnesses as multiple sclerosis, cancer, and AIDS (see Bostwick, 2012). One unexpected finding: the average death rate for opioid overdose was 25% lower in states with legalized medical marijuana than in states without legal access to marijuana, suggesting that the availability of medical marijuana for chronic pain may be associated with lower use of narcotic painkillers (Bachhuber & others, 2014).

Jim Wilson/The New York Times/Redux