Earlier this year, singer and actress Olivia Newton-John, revealed that her breast cancer had returned more than 20 years after her original diagnosis. And in a recent interview with Australia's 60 Minutes, she opened up about the details of her pain—and that she's been using medical cannabis to deal with it.

Originally diagnosed with breast cancer in 1992, Newton-John said in May that her cancer had come back. Initially, the 68-year-old thought she was dealing with back pain. But it turned out that her pain was caused by breast cancer that had returned and metastasized into the bones of her lower back.

“The pain level was really the hardest thing,” she said in the interview. "I was trying to do shows and it was pretty agonizing,” she continued. She says she can walk now, but only short distances.

But, in an interview with Today this week, she says she's not as scared this time around, partly because her daughter is an adult now. “I’ve had a wonderful life," she said, "so I’m not as freaked out as I was when I had a young child.”

Still, treating metastatic cancer and its symptoms is serious business. In addition to undergoing photon radiation therapy, Newton-John says she has been using cannabis grown by her husband to help with the pain caused by her illness. Although it's still a somewhat controversial topic in the U.S. (and illegal at the federal level), some experts believe medical cannabis really can help with chronic pain—especially pain that's related to cancer.

Pain management is one of the few uses for medical cannabis that we actually have solid research on.

"It's extraordinarily useful for pain control," Jordan Tishler, M.D., a medical cannabis expert based in Massachusetts, tells SELF. "A number of studies show that when you compare opiates and cannabis for pain, they’re sort of equivalent in how they work," he says, "but cannabis is much safer." Some research has even shown that cannabis can help patients decrease their use of opiates, a welcome benefit in the context of our current opiate crisis.

"Treatment for cancer pain is one of the indications [for cannabis] that has quite a bit of research on it—including pain that hasn’t responded fully to opioid medication," Dustin Sulak, D.O., founder of medical cannabis education company Healer, tells SELF. But he explains that a fair amount of the research on cannabis and chronic pain comes from the clinical trials for Sativex, a drug approved in several countries outside of the U.S. containing the two major compounds in cannabis—not the plant itself.

That's because it's "very difficult to study cannabis [the plant] as a therapeutic intervention in the U.S." due to its status as a Schedule I drug, Donald Abrams, M.D., an integrative oncologist at UCSF, tells SELF. That designation means the drug has a high potential for addiction and no accepted medical value (according to the DEA). This creates a sort of catch-22 scenario: Researchers have a hard time getting access and funding from the government to study cannabis's potential medical uses because it's a Schedule I substance, which makes it nearly impossible to study whether or not it should actually be a Schedule I substance.

The research we do have, however, is encouraging. In one double-blind placebo-controlled trial published in 2013, those who were on low doses of Sativex reported less pain daily than those in the control group. All of these participants were also taking opioids, but still experiencing refractory pain. An earlier review of Sativex-related research concluded that it improved patient's sleep quality, especially among those with chronic pain conditions.