Drugs used to treat mood disorders block out a stress protein that’s associated with chronic pain, a new study published in Science Translational Medicine finds. The drugs show promise as a treatment for chronic pain in mice, and may prove to be effective in humans when tested clinically.

The stress protein in question, FKBP51, regulates the body’s response to stress. The protein has previously been examined for playing a role in the efficacy of antidepressants, and is generally understood to be associated with post-traumatic stress disorder (PTSD), depression, and anxiety, mainly when there’s a variation in the gene. In addition to its link to mental health disorders, variations in the FKBP5 gene have been associated with physical pain after an injury or trauma.

When the researchers studied mice that had been genetically modified to lack the FKBP51 protein, they found that they experienced less chronic pain from nerve damage and arthritis than mice who still had the protein. “Inhibiting FKBP51 has a very powerful effect in mice with chronic pain,” Dr. Maria Maiarù of the University College London, an author of the study, said in the press release. “Not only does it block the pain from their injury without affecting their normal pain response, it also makes them more mobile. We did not find any negative side-effects.”

A certain group of mood disorder drugs are able to block out FKBP51 as a way of reducing anxiety in patients. So the researchers tested the drug, known as SAFit2, on the mice to see its effect on chronic pain — and found that it indeed helped reduce chronic pain.

Chronic pain has been linked to anxiety and stress before. Research has shown that chronic pain and anxiety share a biological mechanism, so a new treatment involving a FKBP51 blockade might be able to treat both of them at the same time. Scientists still don’t fully understand the causes behind chronic pain, and whether it’s the stress and anxiety that lead to chronic pain or vice versa. For example, one 2015 study found that chronic pain triggers brain inflammation, which in turn may lead to anxiety and depression; other studies have found that anxiety and depression came first, then resulted in chronic pain.

Either way, some 11 percent of Americans suffer from chronic pain, which currently has no treatment, according to the National Health Institute (NIH). And it can have long-lasting effects on the mind and body, as it changes DNA in the brain and immune system, and may contribute to far more conditions than previously believed.

“Who wouldn’t want a treatment that relieves chronic pain while also making you less stressed?” Dr. Sandrine Géranton, senior author of the study, said in the press release. “This was an experimental study with mice, but if this could be successfully translated into a treatment for patients, it would be a win-win.”

Source: Maiarù M, et al. Science Translational Medicine, 2016.