While we’ve long known that the color green has a calming effect, a recent study discovered that green light activates opioid receptors in the brains of mice, and significantly reduced pain.

As the US continues to struggle with widespread opioid addiction, the potential of green light to decrease or eliminate pharmaceutical painkillers could be a game-changer. “Exposure to an environment rich in the color green (such as forest bathing) can decrease physiological and psychological pain,” said the study’s authors.

Previous studies have linked the color green to positive emotions and pain reduction in those suffering from chronic migraines and fibromyalgia. The latest research, published in the journal Science Translational Medicine, focuses on exactly how green light exposure leads to pain reduction and how the results could be replicated in humans.

Initially, the study experimented with arthritic mice and found that full-field green light exposure helped the rodents to feel more at ease. Next, the researchers wanted to identify which photoreceptors in the eyes were responsible for linking the color to the animals’ brains. After blocking cone, rod, and retinal ganglion cell receptors, they concluded that cones mediated the painkilling effect of verdant light.

Next, the authors studied the neural process from the cones in the eyes to the ventral lateral geniculate nucleus (vLGN), located in the brain’s thalamus. Neurons in the vLGN, mediated by a signaling protein called PENK, communicated with the dorsal raphe nucleus (DRN), a part of the brain that plays a critical role in pain control.

The study confirmed previously held research into the pain-relieving powers of green light. But the follow-up research may answer the most important question, Does exposure to green light alleviate pain in humans?