As eight states plus the District of Columbia have moved to fully legalize recreational marijuana, debates on the merits of legalization have focused on the effects of marijuana use on individuals and society. The National Academies of Sciences, Medicine and Engineering have brought a great deal of clarity to the situation with an encyclopedic report summarizing pretty much everything researchers know (and don't know) about the health effects of marijuana use. For the 395-page report, a team of dozens of drug policy experts at some of the nation's most prestigious universities analyzed 24,000 scientific papers to arrive at more than 100 conclusions regarding the effects of marijuana use. The committee found strong evidence showing marijuana is effective at treating chronic pain in adults. Given the current public health crisis involving tens of thousands of deaths annually because of painkiller overdoses, this is a potentially significant finding. The report also turned up strong evidence that marijuana is effective at treating nausea and vomiting, [as well as] muscle spasticity. The literature shows limited evidence that marijuana use is linked to the use of other substances. The report does not address the implications of these findings for current legalization debates. The researchers do, however, state emphatically that the current designation of marijuana as a Schedule 1 controlled substance ... is one of the chief barriers to conducting more badly needed research.