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The National Academies of Science, Engineering, and Medicine has recently released a meta-review of the scientific literature available on the health impacts of marijuana. The study is notable for two very different reasons. The first is its scale. The researchers reviewed abstracts of over 10,000 studies to form more than 100 conclusions, drawing on the best peer-reviewed research on the impacts of cannabis use conducted since 1990. But the study was also notable for its admission of just how much we don’t know. “A lack of scientific research,” the study warns, “has resulted in a lack of information on the health implications of cannabis use.” Although this meta-analysis draws on research that is constrained by federal limitations on cannabis research, it represents the best scientific consensus on marijuana science today.

The report considers several broad categories, including therapeutic effect, cancer, cardiometabolic risk, mental health, respiratory disease, immunity, and injury and death. Although the report is not entirely sanguine with regards to the health impacts of marijuana, it broadly confirms claims made by marijuana advocates for years: smoking too much weed probably isn’t really good for, but smoking a little weed isn’t too bad. And the stuff can help with all kinds of pain and ailments.

Among key findings from the report:

  • Conclusive evidence of effective treatment of chronic pain, chemotherapy-induced nausea, and multiple sclerosis
  • Moderate evidence that marijuana consumption has no statistical association with lung cancer
  • Substantial evidence that marijuana consumption is associated with chronic bronchitis
  • Substantial evidence associates cannabis use with automobile accidents
  • Moderate evidence suggesting cannabis use has negative effects on learning and memory

The report also set future research priorities, including further research into alternate delivery forms, such as vaping. It highlights the need for clear and universally recognized protocols for quality cannabis research and suggests that regulatory reforms that allow for broader cannabis research have the potential to form a better knowledge base from which science-based policy decisions can be made.