A sleep supplement widely used to treat insomnia could help reduce reliance on some of the most common and potentially harmful pain medications, new research from the University of Sydney suggests. 

Published in PAIN, the study found melatonin can reduce chronic musculoskeletal pain with effects in a similar range to medications such as opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol. 

With musculoskeletal pain affecting up to 47 percent of people globally, the findings point to a low-cost, widely available option that could shift how chronic pain is managed. 

“Melatonin is already in people’s homes, it’s inexpensive, and we know it’s safe,” said lead author and PhD student Kangchao Wu from the Musculoskeletal Research Hub at the Charles Perkins Centre and the School of Health Sciences. 

“What’s exciting is that melatonin may also help manage chronic pain, opening the door to reducing reliance on medications that come with more risks.”

The research highlights the growing potential of drug repurposing – using existing treatments in new ways to deliver faster, more accessible health benefits. 

“We’re taking a medication we already understand and applying it to a problem that affects a huge proportion of the global population,” said co-author Professor Paulo Ferreira, Director of the Musculoskeletal Research Hub. 

The study analysed data from 2028 adults across 23 randomised controlled trials conducted in countries including the United States, Russia, Brazil, Egypt and China. Participants included people with conditions such as low back pain, osteoarthritis and fibromyalgia, as well as those recovering from surgeries including joint replacements and spinal procedures. 

On average, the study found that melatonin reduced pain by around nine points on a 0-100 scale, with the most rigorous trials showing reductions closer to 10 points, a similar magnitude to widely used pain medications. 

The supplement also improved sleep quality, reinforcing the well-established link between pain and sleep. 

“For many patients, pain doesn’t exist in isolation and is closely tied to poor sleep,” Mr Wu said. 

“Melatonin appears to target both, which makes it particularly useful for people managing chronic pain.”

Across the trials, the dose and timing of melatonin varied depending on the condition and setting. For chronic musculoskeletal pain, doses typically ranged from 3 to 10 mg, with 3 mg per day the most commonly used. For postoperative pain, doses ranged from 1 to 10 mg, with 5 to 6 mg most common. Melatonin was generally taken at bedtime or up to one hour before sleep. 

The researchers did not find evidence of a clear dose-response relationship, meaning no single “best” dose can be recommended from the current evidence.