Could cannabis treat cancer someday? Here's what the science says so far

Research into the potential medical benefits of cannabis has exploded in recent years, raising one intriguing question: Could cannabis treat cancer?  

It may sound far-fetched that weed — the high-inducing plant that propagandists once warned would cause "reefer madness" — could contain ingredients that shrink tumors. However, experts told Live Science that there is some early evidence that some cannabinoids, the active ingredients found in cannabis, do have anticancer effects.  

"There's no two ways about it: [Cannabis] has anticancer properties," Wai Liu, a senior research fellow at St George's, University of London, told Live Science. "But the problem is, how do you translate that into the clinic — and that's the difficult question to address." 

Here's what we know so far about Mary Jane's cancer-fighting powers.

Related: Runners enjoyed their workouts more after using cannabis, but physically floundered

What are cannabinoids, and can they treat cancer?

The cannabis plant comes in more than 700 varieties, with famous examples including Cannabis sativa and Cannabis indica. Cannabis plants contain substances called cannabinoids, or chemicals that interact with the endocannabinoid system in the brain. Endocannabinoids made by the body help regulate a plethora of biological functions, including eating, learning and pain recognition. 

Plant-made cannabinoids, of which more than 100 have been identified by scientists, plug into this same system and affect its activity. These plant-made molecules include tetrahydrocannabinol (THC), which is largely responsible for the characteristic "high" associated with cannabis, and cannabidiol (CBD), which doesn't produce a high but has been studied for its potential medicinal effects.