There's really no other way to put this: the National Cancer Institute, which operates under the U.S. Department of Health, just confirmed that cannabis kills cancer cells.

In a recent update to the department's Physician Data Query (PDQ) cancer information summary on cannabis and cannabinoids, the NIC reported that pre-clinical trials have demonstrated that cannabinoids, active components of cannabis, inhibit tumor growth by killing cancer cells, blocking cell growth, and preventing the development of blood vessels that tumors need to grow.

"Laboratory and animal studies have shown that cannabinoids may be able to kill cancer cells while protecting normal cells," the organization wrote.

Not only has research established that marijuana contains medicinal properties that reduce inflammation of the colon in mice, but the substance has even shown potential for reducing the risk of colon cancer, as well as being effective in the treatment of the disease. Marijuana's effect on chronic pain and nausea—which many cancer patients experience throughout the treatment process—were additionally referenced in the PDQ.

Further, the department included a note about the findings of another laboratory study that concluded that cannabidiol (CBD), a non-psychoactive cannabinoid found in marijuana, killed breast cancer cells "while having little effect on normal breast cells."

"Studies in mouse models of metastatic breast cancer showed that cannabinoids may lessen the growth, number, and spread of tumors," researchers added.

The NIC also recognized that marijuana use was associated with a 45 percent reduction in the incidence of bladder cancer, as noted in an analysis of more than 84,000 people by the California Men's Health Study.

Asked about the recent changes to its executive summary, NIC spokesperson Katherine Jenkins told ATTN: that "the PDQ Editorial Boards conduct regular reviews of newly published peer-reviewed literature to maintain the currency of the PDQ cancer information summaries," adding that the PDQ on cannabis and cannabinoid was last updated on August 7.

Still, the organization did not fully condone the use of cannabis for cancer treatment; instead, it recommended that further research is needed. "At present, there is insufficient evidence to recommend inhaling cannabis as a treatment for cancer-related symptoms or cancer treatment–related side effects."

This is not the first study to report about the remarkable relationship between cannabis and cancer. Last year, scientists at the University of East Anglia in the United Kingdom released a study that linked THC, the main psychoactive component of marijuana, to significant reductions in tumor size. Following the announcement, researchers said they hoped that the results would lead to the development of a synthetic equivalent that could mimic THC's anti-cancer properties.

"There has been a great deal of interest in understanding the molecular mechanisms behind how marijuana, and specifically THC, influence cancer pathology," Dr. Peter McCormick, a researcher at the UEA School of Pharmacology, said. "By identifying the receptors involved we have provided an important step towards the future development of therapeutics that can take advantage of the interactions we have discovered to reduce tumor growth."

A 2009 study published in the Journal of Clinical Investigation similarly found evidence to support that idea that cannabis could be used in brain cancer treatment. Researchers at Complutense University in Spain announced that mice with brain cancer showed reduced tumor size after they were administered THC.

Future studies

"There have been previous reports to this effect as well," the study's co-author, Guillermo Velasco, wrote. "So this is yet another indication that THC has an anti-cancer effect, which means it's certainly worth further study."

That phase—"yet another"—is increasingly common among marijuana studies, and that should give everybody pause for thought. With study after study showing that cannabis has anti-cancer properties, it is no wonder that the NIC and other federal agencies have recently shifted their position on the substance. It is worth exploring, to be sure, and more people appear to be realizing that.