Opioids are no better at treating chronic pain than over-the-counter pain relievers such as ibuprofen and naproxen, according to a study that raises questions about how often the drugs are prescribed, considering the risks they pose.

The study, published Tuesday in the Journal of the American Medical Association, was an analysis of nearly 100 studies on the effectiveness of opioids at treating chronic non-cancer pain. The studies compared opioids to a placebo as well as other pain-relieving drugs. The researchers concluded that opioids are slightly better than a placebo at treating pain and provide similar benefits as non-steroidal anti-inflammatory drugs such as ibuprofen and naproxen. The findings also suggest opioids are no better than antidepressants for treating pain, but that they may provide better pain relief than anticonvulsant drugs such as gabapentin and pregabalin.

“There was this dramatic increase in opioid prescribing in the 1990s and early 2000s and only now, 20 years later, is it being made clear that these medications may not work at all, or if they do have a benefit, it’s very small,” said Nav Persaud, a family doctor at Toronto’s St. Michael’s Hospital and a scientist at the hospital’s Li Ka Shing Knowledge Institute. He was not involved in the study.

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According to the study, the research also showed that the modest benefits provided by opioids seemed to wane over time, for reasons that aren’t entirely clear. Despite this, many patients stayed on the drugs for long periods, suggesting they may have experienced difficult and painful withdrawal symptoms if they attempted to stop taking them, said Jason Busse, lead author of the study and associate professor in the department of anesthesia at McMaster University in Hamilton, Ont.

“[Opioids] won’t work for most patients. For those that do, those benefits will often attenuate over time,” he said. “So why is it that so many patients, when started on long-term opioid therapy, will continue?"

Much of the focus of Canada’s opioid crisis is currently fixed on the rising number of deaths and hospitalizations caused by fentanyl overdoses. But prescription opioids are still an important part of the problem that shouldn’t be ignored, Dr. Busse said, especially since some evidence suggests that many people who overdose on opioids had, at the time of death or during a previous point in their lives, received a prescription for an opioid painkiller.

Dr. Busse said the findings underscore the need for better access to other treatments to manage pain, such as mindfulness therapy. He said he’s also concerned that many people are promoting cannabis as an effective treatment for chronic pain, although there is little clinical data to back this up. He said patients and clinicians should wait until there is sufficient evidence before using cannabis for pain in order to prevent problems similar to the opioid crisis from occurring.