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WASHINGTON — Researchers from Yale University believe they have deciphered the neurological mechanism that causes the ‘‘munchies,’’ that inexplicable urge to eat that has led generations of marijuana users to consume untold numbers of nachos, Twinkies, and Doritos.

The phenomenon appears to be driven by neurons in the brain that typically involve suppressing the appetite, according to a paper published Wednesday in the journal Nature. When responding to marijuana, however, neurons that normally turn off hunger pangs instead made users ravenous — at least when those users were transgenic lab mice.

Tamas Horvath, the study’s lead author and a Yale professor and neurobiologist, likened the reaction to hitting a car’s brakes and accelerating instead.


‘‘It fools the brain’s central feeding system,’’ Horvath said in an announcement accompanying the research, which was funded in part by the National Institutes of Health and the American Diabetes Association. ‘‘We were surprised to find that the neurons we thought were responsible for shutting down eating were suddenly being activated and promoting hunger, even when you are full.’’

In an interview Tuesday, Horvath said that while the link between cannabis and increased appetite itself is not surprising — either to researchers or to pot smokers — ‘‘what drives that, nobody has ever really known. We accidentally bumped into that.’’

Researchers have long known that activating cannabinoid receptor 1, or CB1R, on brain cells can contribute to overeating. They also have documented that the active ingredient in marijuana, tetrahydrocannabinol, has the ability to trigger hunger. But in recent years, they have continued to investigate the mechanisms underlying the hunger effect.

In a 2005 study, scientists found that cannabis use rendered specific neurons in the brain ‘‘more excitable’’ and inhibited the appetite-suppressing hormone leptin. In 2009, research out of Japan found that marijuana might interact with taste receptors to enhance the sweet taste in foods, thus boosting cravings. In a study last year in Nature Neuroscience, European scientists found that exposing mice to tetrahydrocannabinol, or THC, enhanced their ability to smell certain foods and led them to eat more.


Beyond merely figuring out the neurological mystery behind the munchies, Horvath and other scientists are hoping that a clearer understanding of the appetite triggers in the brain could lead to an array of practical uses. For instance, it could lead to new medications, perhaps even a pill, to jump-start hunger in cancer patients who often lose their appetite during chemotherapy.