The science behind getting the ‘munchies’ explained

Dear Doctor: I’ve read stories about Girl Scouts selling hundreds of boxes of cookies outside pot shops to people who are anticipating the munchies. My question is: What is it about cannabis that causes that kind of hunger?

Dear Reader: It’s a toss-up which effect of using cannabis is better known — the fact that it alters mood and perception, or the raging hunger that users experience, known as the munchies. Research into the psychoactive effects and mechanisms of the drug dates back decades. Now, thanks to research published in 2015 by scientists at Yale University, we finally have an answer to the munchie conundrum.

According to the World Health Organization, cannabis is the most widely used and trafficked illicit drug in the world. In the United States, it is recognized as a Schedule I controlled substance. However, growing numbers of states are passing laws that permit medical and/or recreational use of the drug, which is how some enterprising Girl Scouts came to set up shop outside cannabis dispensaries.

Cannabis looks and grows like a weed, but it’s actually quite complex. Researchers have isolated more than 400 different chemical compounds and entities within the plant, a number of which are being studied for medicinal qualities. In fact, the mechanisms revealed in the research that decoded the munchies show promise in helping people who need help with appetite, such as cancer patients undergoing chemotherapy.

The active ingredient in cannabis is tetrahydrocannabinol, or THC. It is chemically similar to anandamide, a neurotransmitter that naturally occurs in our brains. In fact, the molecular structures of THC and anandamide are so similar that THC can attach to and activate sites known as cannabinoid receptors, which are located on neurons throughout the brain.

Once THC enters the blood, either by smoking or ingesting, it takes just a short time for it to bind to receptors and begin to affect a range of cognitive processes in the brain.

In 2014, a team of European researchers discovered that THC fits into a neural structure in the brain known as the olfactory bulb. The result is an increased sense of smell, which the scientists believed could lead to an increase in appetite. A year later, a team of neuroscientists from the Yale School of Medicine published a surprising set of findings that focused on the drug’s effect on the appetite centers of the brain.

Working with genetically modified mice, the scientists found that some of the compounds in cannabis actually trick the appetite center of the brain. Through a series of complex steps, those compounds subvert the very mechanism that, when working properly, tells the mice that it’s time to stop eating. As the lead researcher of the study put it in a press release, “It’s like pressing a car’s brakes and accelerating instead.”

Scientists are intrigued by this newest study. A compound that flips a biochemical switch and makes a brain process do the opposite of what was intended is indeed unique. However, the consensus is that this, like that olfactory bulb discovery, is just one piece of the complex munchies mystery.