Pain is the human bodyguard, the cop on the beat racing to the scene, sirens wailing, shutting down traffic. You've been cut, burned, broken: pay attention, stop the bleeding, apply heat, apply cold, do something. It's one of life's most primitive mechanisms, by which even the simplest creature, if it has anything like a central nervous system, learns to avoid danger, stay out of bad neighborhoods, hunker down to give itself time to heal. Pain is protective. Don't do that, it commands and the command is usually a wise one. So this sensation we seek most to avoid is in fact one of the most essential ones for our survival.
But what happens when pain goes rogue, when it sends off false alarms so that all the sirens keep sounding, all the cops keep coming, all the hurts keep hurting? If even benign stimuli get distilled down to a single, primal Ouch!, then pain ceases to be adaptive. Rather than saving lives, it wrecks them. Rather than helping you get well or stay safe, it becomes an illness in itself. The result: persistent, unceasing torment.
That's the situation that more than 76 million Americans face. Their pain can last for days or even weeks at a time, then dissipate, only to return. The problem may be caused by something as common as arthritis, an inflammation of the joints that makes them throb with discomfort. The issue could be fibromyalgia, in which a breakdown of pain signals leaves joints, muscles and tissues hypersensitive. It may be a nerve disorder known as neuropathy, triggered by diseases as diverse as cancer and diabetes. It may be that the cause is unidentifiable. Many cases of chronic pain remain unexplained, but they hurt all the same.
There's no telling who the victims of chronic pain will be, but there are ways of determining who is at highest risk. About 10% of people who have surgery, even relatively routine procedures such as knee or back operations, for example, will never be the same again, suffering a lifetime of generalized pain that may start from the incision site but is eventually diffused to other parts of the body. Around 20% of cancer patients will continue to feel pain two years after the surgery or chemotherapy that may have saved their lives. For all of them, pain is not merely a symptom but a disease in itself, one that doctors have only recently come to recognize.
But recognizing a disease is only a prelude to treating it, and doctors admit that while they're pretty good at relieving the acute pain that occurs immediately after surgery or an injury, they are usually stymied by the chronic kind. The most common complaint doctors hear from their patients is about pain that will not quit, and more than 80% of those people never receive treatment or at least not an effective one. About a decade ago, physicians took the first step toward acknowledging the prevalence of pain and their inadequate ability to address it by including pain assessment as a vital sign along with blood pressure, respiratory rate, heart rate and temperature. "As a clinician, I'm frustrated, and I'm sure many patients are, because we do a very poor job in terms of providing relief for chronic pain," says David Borsook of the McLean Hospital and Harvard Medical School.
To address that frustration, this summer, an expert panel convened by the Institute of Medicine the independent scientific advisory arm of the National Academies will release a report on the latest advances in understanding chronic pain and highlight the need for an all-encompassing approach that treats it as a disease of both brain and body. A strategy that lays bare the multitude of body systems involved in maintaining a world of chronic hurt also presents a multitude of treatment opportunities for science to exploit.
Brain-imaging studies and research in genetic and molecular biology, for example, suggest that a brain in chronic pain looks and acts differently from a normal brain and that the phenomenon can even run both ways: haywire circuits cause the brain to register persistent pain, which in turn leads to changes perhaps permanent in the way the brain and body work. All this suggests entirely new routes toward eliminating pain or at least managing it better.
"There has been a shift in thinking away from pain as only a sensory experience," says Dr. Clifford Woolf, a neurologist at Children's Hospital Boston. "Rather than targeting the suppression of pain as a symptom, the best treatment now has to be targeted at preventing pain as a disease. That insight really changes the way we understand pain."