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Stoner Science is Still Trying to Explain the Munchies

But we’re getting closer to understanding why pizza is irresistible when you’re high.
​Image: Flickr/​Dank Depot

Everyone knows that smoking pot makes you hungry. Whether or not you reach for the powdered doughnuts is only a matter of time. But what, exactly, occurs in the brain to cause this sudden onset of gluttony after getting high on cannabis is still somewhat of a mystery.

Numerous researchers have tried to explain why the activation of cannabinoid-1 (CB1) receptors in the brain by THC, marijuana's key ingredient, makes you crave food. The latest attempt comes from from researchers at the University of Yale School of Medicine, who found that stimulating CB1 receptors in mice caused neurons that usually release hunger-satiating chemicals to make them feel hungry instead.

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"The question was: how could a neuron that a minute before was suppressing your appetite turn into the driver of your hunger?" said Tamas Horvath, one of the authors of a new paper published today in Nature. "We found that the chemical that [the neurons] release normally promotes satiety, whereas the chemical that they release after cannabis exposure is an opioid peptide that, acting through a different pathway, promotes hunger. It's that simple."

A strange and counterintuitive finding, to be sure—and it's not the only explanation that's been floated by researchers over the years. One recent study suggested that CB1 receptors increase sensory perception, making food smell especially irresistible. But in 2005, a study published in Neuron suggested that active CB1 receptors inhibited leptin, an appetite suppressant. Are the munchies a function of these combined effects? Or some and not others? Just what the hell is going on when your brain is on drugs?

"I don't know, to be honest," Horvath said, laughing. "Perhaps we've bumped into a driver of cannabis-induced hunger that was previously not suspected, but we'll see. It could be much more complicated, but when it comes to feeding, it could also be much more simple than people thought. If you look at the literature, there are thousands of papers on subjects related to this issue."

Much more work is needed before we can say that we know how the munchies happen, Horvath said. How pot makes neurons completely switch their function from suppressing your appetite to stimulating it is just one of many mysteries that need to be examined. It's also worth noting that the study was done using mice, and the compounds used to stimulate the neurons were made for animals, not people.

Horvath and his colleagues' work may well be a leap forward in our understanding of pot's effect on the brain, but their results aren't yet conclusive. The brain is a mysterious organ, and as scientists and stoners alike can attest, marijuana only makes things tougher to understand.