Other drugs and treatments such as physical therapy or ice may work better for non-cancer pain, the researchers found. Yet when opioids fail to control pain, doctors often simply raise the dosage. This can help lead to a cycle of dependence and addiction.

The opioid epidemic continues to worsen despite years of warning an attention. Last year, 70,000 people died from drug overdoses, the Centers for Disease Control and Prevention reports. The majority of drugs involved were opioids such as fentanyl.

Opioids are most important for use in treating the pain associated with cancer, and medical groups all support their use for cancer pain. But they are often prescribed for back pain, headaches, post-surgical pain and other conditions.

Jason Busse of McMaster University in Ontario and colleagues went through much of the known research on how well opioids work.