Scientists Reveal Why Marijuana Gives You the Munchies

Scientists have discovered just how marijuana causes "the munchies."

Although it is no secret that marijuana can make a person feel more hungry, new research detailed in the journal Scientific Reports by Washington State University scientists found that it actually activates specific hunger neurons in the brain, triggering a mechanism that increases appetite.

Not only does this inform scientists on how marijuana affects the brain, but the findings could drastically help scientists develop treatment paths for disorders such as anorexia.

In the United States, marijuana is the most commonly used federally illicit drug (recreational use of marijuana is currently legal in 24 states and in Washington, D.C.). According to statistics from the Centers for Disease Control and Prevention (CDC) around 18 percent of Americans used marijuana at least once in 2019.

When consumed, it often causes a commonly known phenomenon known as "the munchies," a sharp spike in the desire to eat. During a bout of the munchies, a person may experience a particular craving for foods rich in salt, sugar or fat.

Scientists came to the new findings by assessing the effects marijuana had on mice. After exposing the rodents to a vaporized sativa of the drug, calcium imaging technology—a similar technique to an MRI—showed that marijuana activated a collection of cells in the hypothalamus area of the brain.

This occurred when the rodents were anticipating and consuming food. However, this did not happen in the mice that were not exposed to the drug.

"When the mice are given cannabis, neurons come on that typically are not active," Jon Davis, an assistant professor of neuroscience at the university and corresponding author on the paper said in a summary detailing the findings. "There is something important happening in the hypothalamus after vapor cannabis."

Other research has found that the key ingredient tetrahydrocannabinol, or THC, is responsible for this feeling. This ingredient is responsible for the "high" that people feel, but it also triggers the complex signaling networks in the brain. This network is responsible for deciding a number of things that go on in the body, including emotions, sleep, pain, and of course, hunger.

This new research is the first time calcium imaging has been used to understand the effect of marijuana on the brain's reactions to food.

"We now know one of the ways that the brain responds to recreational-type cannabis to promote appetite," Davis said.

The researchers also looked at the cannabinoid-1 receptor—regions of the brain that mediate some of the effects of the drug. They discovered that this region of the brain controlled some feeding cells in the hypothalamus when the mice were exposed to the drug.

Following these findings, the scientists used a chemogenetic technique that acted like a "light switch" to the rodent's brain. Neurons were "turned on" when the mice had been exposed to marijuana, whereas when they had not, the neurons were "turned off."

These new findings are the latest in a long research initiative from the lab, aiming to find out more about how marijuana affects humans. Previously, the lab discovered how marijuana caused genetic changes in the hypothalamus.