Cannabis has long been associated with intense food cravings, but new research suggests the phenomenon extends well beyond human experience.
Researchers at the University of Oregon have discovered that cannabinoids trigger the same appetite-amplifying effects in worms as they do in people, pushing both toward calorie-dense food choices.
The research team immersed nematodes (roundworms) in the endocannabinoid anandamide before placing them in a T-shaped maze. One branch of the maze contained the worm equivalent of junk food; the other offered a low-calorie alternative.
Although worms already show a natural inclination toward high-calorie food, those exposed to anandamide displayed a significantly stronger preference, spending more time on that side of the maze compared to untreated worms.
Shawn Lockery, the study's corresponding author, said: "The endocannabinoid system helps make sure that an animal that's starving goes for high fat and sugar content food.
"This increase in existing preference is analogous to eating more of the foods you would crave anyway. It's like choosing pizza versus oatmeal."
In follow-up experiments examining how anandamide influenced the worms' neurons, the team found that the affected worms were also more sensitive to the scent of high-calorie food.
Given that humans and nematodes last shared a common ancestor hundreds of millions of years ago, the parallel response to cannabinoids across both species points to just how ancient the endocannabinoid system actually is.
"Nematodes diverged from the lineage leading to mammals more than 500 million years ago," Lockery said. "It is truly remarkable that the effects of cannabinoids on appetite are preserved through this length of evolutionary time.
"It's a really beautiful example of what the endocannabinoid system was probably for at the beginning."
Lockery also proposed that nematodes could prove valuable in future research and in the development of pharmaceuticals that target cannabinoid receptors in the body.
"The ability to rapidly find signaling pathways in the worm could help identify better drug targets, with fewer side effects," he said.
The study appeared in Current Biology.