Last week, the National Academies of Sciences, Engineering, and Medicine released the most comprehensive report on the science of cannabis to date. While there were some positive takeaways, the report's list of potential risks far outweighed the potential benefits of medical marijuana.

The researchers who wrote the report noticed that discrepancy, too. And they say it has to do with an institutional bias involving cannabis research. Basically, the mandate of the National Institute on Drug Abuse (NIDA) - the group in charge of okaying or denying cannabis research projects in America - is causing cannabis studies to skew negatively.

"In the United States, cannabis for research purposes is only available through the NIDA Drug Supply Program," the report reads. "The mission of NIDA is to 'advance science on the causes and consequences of drug use and addiction and to apply that knowledge to improve individual and public health,' rather than to pursue or support research into the potential therapeutic uses of cannabis or any other drugs...As a result of this emphasis, less than one-fifth of cannabinoid research funded by NIDA in fiscal year 2015 concerns the therapeutic properties of cannabinoids."

In other words, approximately 80 percent of approved studies in 2015 skewed negative, while only 20 percent looked at the potential health benefits of marijuana.

Researchers concluded that NIDA's "focus on the consequences of drug use and addiction constitutes an impediment to research on the potential beneficial health effects of cannabis and cannabinoids." So we likely won't know the whole story of marijuana's health effects unless the federal government allows broader research.

The report also noted that problems with the cannabis available for research could be skewing studies as well. From 1968-2016, only the University of Mississippi was allowed to grow marijuana for scientific research. That means scientists haven't been able to investigate the sorts of cannabis strains, extracts, edibles and concentrates that people are using medicinally or recreationally in legal states.

And the chokehold on supply has also diminished the quality of the product. The report states, "Because of restrictions on production and vicissitudes in supply and demand, federally produced cannabis may have been harvested years earlier, is stored in a freezer (a process that may affect the quality of the product)."

So we need to take a number of the report's findings with a grain of salt because cannabis research has been colored by the NIDA's emphasis on addiction. And like some of the plants being studied, a lot of the findings are probably stale.