For the first time, scientists have identified exactly what happens in the brain after using marijuana that causes the “munchies,” a new federally funded study shows.
Researchers at Washington State University (WSU) published the findings in the journal Scientific Reports, revealing how cannabis activates a specific cluster of neurons in the hypothalamus region of the brain that stimulates appetite.
The hunger-inducing effects of marijuana have been well-understood by consumers, but now the results of the new animal research offer insights that could help lead to the development of targeted therapeutics for people with conditions such as anorexia and obesity.
After mice were exposed to vaporized cannabis, researchers used calcium imaging technology (similar to a brain MRI) to track changes in neuron activity. They found that marijuana vapor attached to cannabinoid-1 receptors in the brain and activated so-called “feeding” neurons in the hypothalamus called Agouti Related Protein neurons.
“The appetite promoting effects of cannabis sativa have been recognized for centuries, however, surprisingly, the biological mechanisms that underlie this process have remained largely unknown.”
“When the mice are given cannabis, neurons come on that typically are not active,” Jon Davis, an assistant professor of neuroscience at WSU, said in a press release on Tuesday. “There is something important happening in the hypothalamus after vapor cannabis.”
“We now know one of the ways that the brain responds to recreational-type cannabis to promote appetite,” he said.
Put in more scientific terms, the study showed “pharmacological activation of CB1R attenuated inhibitory synaptic tone onto hunger promoting Agouti Related Peptide (AgRP) neurons within the MBH,” or mediobasal hypothalamus.
“Based on these results, we conclude that MBH neurons contribute to the appetite stimulatory properties of inhaled cannabis,” the authors said.
Importantly, the study involved vaporized whole-plant marijuana, rather than injected THC as in prior animal research, so the findings are believed to more accurately depict brain activity that’s applicable to people who consume cannabis.
The study was partly funded by two federal agencies, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and the U.S. Department of Agriculture (USDA). Researchers also received funding from alcohol-related state revenue.
The phenomenon of the munchies has long intrigued scientists. A 2019 study, for example, found that sales of commonly munched on products like ice cream, cookies and chips tend to go up after states legalize cannabis.
Despite that, a 2022 study determined that adult-use legalization is actually associated with decreased levels of obesity despite the fact that cannabis is well-known appetite stimulator.
Last year, a meta-analysis also found that people who use marijuana are about half as likely to develop type 2 diabetes.
Photo courtesy of Martin Alonso.