Imagine you are a doctor treating a patient who has been in nearly constant pain for four years, ever since the day he sprained his ankle stepping off a curb. Physical therapy only briefly dulled the agony. Painkillers were not much better, and the most effective drugs made your patient exhausted and constipated. He is now depressed, sleeping poorly and having difficulty concentrating. As you talk with him, you realize that his thinking also seems impaired. Your exam confirms that the original injury has healed. Only pain and its consequences remain—and your options for helping this man are running out.
This scenario plays out every day in doctors’ offices around the world. Fifteen to 20 percent of adults worldwide suffer from persistent, or chronic, pain. Half the primary care patients who develop a chronic pain condition fail to recover within a year, according to surveys conducted by the World Health Organization. Common causes of such unrelenting discomfort include physical trauma, arthritis, cancer, and metabolic diseases such as diabetes that can damage nerves. In many cases, however, the pain’s origins are mysterious.