In the short term, pain keeps you alive. It's an essential warning signal, a command that is impossible to ignore. When you yank your finger off a hot stove—or sit down to get the pebble out of a shoe—pain is doing its job.
When the alert system goes awry, chronic pain may set in. It can arise mysteriously, persist for a long time and be very difficult to treat. Sometimes the cause is obvious. But pain's origin may be elusive—an inexplicable headache or a bad back that won't stop hurting. Finding surefire treatments has been difficult because the phenomenon is so complicated. Emotions, memory and expectations all influence chronic pain, and in turn are influenced by it.
Because persistent pain is so complex, a cure for it is not yet on the horizon. But while we wait, a new understanding of why we hurt offers opportunities to use our minds to soften the sting.
Heartburn and Heartbreak: It's All Connected
When you are in agony, the last thing you want to be told is that it's all in your head. But in truth, pain does come from your head, in a group of interconnected brain regions known as the pain matrix. Some regions are involved in delivering descriptive information about the feeling—where it is, how intense it is, whether it's a dull soreness or a sharp prick. Another part, the anterior cingulate cortex, registers the unpleasant "hurt" of pain. It connects the physical sensation of pain to feelings of distress.
Interestingly, the anterior cingulate cortex doesn't distinguish between psychic and bodily injury—it lights up whether you've been hit in the stomach or hit by rejection—and is sensitive to your state of mind. "It is particularly dampened by good mood and enhanced by a bad mood," says M. Catherine Bushnell, director of the McGill University Centre for Research on Pain. "Change the mood, and it changes the pain." One of Bushnell's patients had brain damage that destroyed sensory regions but left his cingulate intact. When he was pinched and prodded with his eyes closed, he didn't know if it was his left arm or toe that hurt, says Bushnell. "All he knew was that he didn't like it."
The same area apparently influences empathy as well. Researchers in England studied happy couples' responses to each other's twinges. When one partner watched the other endure pain, his or her cingulate responded. The higher the person scored on a test of empathy, the stronger the response. In addition, the more empathetic you are, the more vividly you anticipate your own pain: In a sense, you're empathizing with your future self.
Though people with chronic pain are often presumed to be neurotic, the idea of a "pain-prone personality" is not well supported by research. "The evidence is quite mixed," says Frank Keefe of Duke University Medical Center's Pain Prevention and Treatment Research program. "If you treat the pain, some of the personality factors that supposedly caused it actually improve." In other words, pain might make you grumpy or high strung, rather than grumpiness predisposing you to pain.
On the other hand, "catastrophizing"—focusing on the worst possible scenario—amplifies the hurt. People who catastrophize believe that the ache is unbearable, and that they are beyond help. It's not just anxiety: Thinking this way can actually increase painful sensations. Brain scans show that catastrophizers have heightened activity throughout the pain matrix. While personality traits—or experiences like trauma—can predispose people to catastrophize, it is a habit of mind rather than an ingrained characteristic. As a result, it can be changed through behavioral techniques that demonstrate to sufferers that they have some control over their discomfort. Says Keefe, "If you drive down catastrophizing, it's like giving a drug—you can actually see a change in the pain."
The Bad News: You Learn to Suffer
Just like muscles, brain circuits grow stronger when you use them—great when you're learning to play the piano, but terrible in the case of a constantly aching joint. "Pain pathways are like a trail in the forest," says Gavril Pasternak, director of molecular neuropharmacology at Memorial Sloan-Kettering Cancer Center in New York City, "If you have a path that is already worn, it is easier to follow and it becomes strengthened."
Through the same neurological process that makes you gradually get better at hitting a racquetball or driving a stick shift, your brain "gets better" at perceiving the pain—you become more sensitive and more likely to register a poke or a twinge as painful. Eventually, people with chronic pain disorders such as fibromyalgia (which affects joints and soft tissues) can find even mild sensations agonizing. Imaging studies reveal what's going on: A gentle touch causes brain areas that process pain to react. Similar findings have been reported in people with unexplained chronic lower back pain. It's not a conscious process—it's one way the brain naturally responds to repeated stimulation.
Many people who have lost a limb cope with a similar problem. They feel as though their missing body part still hurts. That phantom limb pain often echoes the injury that led to the amputation. Similarly, torture survivors may feel a persistent ache in the regions of the body that were abused. The pain has been seared into the brain circuitry, even though the injury has long since healed.
The Good News: You Can Learn Not to Feel the Burn
Thankfully, like other things you've learned, you can sometimes "forget" chronic pain. Pathological forms of learning, also involved in problems like addictions, seem to be especially hard to undo, but there's some evidence they can be halted or even reversed.
In one study, people who had lost a limb immediately took memantine, a drug that blocks memory-encoding receptors. Usually, more than two thirds of amputees have phantom pain, but only 20 percent of those treated with the medication developed it, says Herta Flor, professor of neuropsychology at the University of Heidelberg in Germany. But the drug doesn't have the same effect once phantom pain has set in. Other research suggests that the cough medicine dextromethorphan, a related drug, may relieve fibromyalgia pain. Don't rush out to buy a bottle just yet, as it's not a practical treatment—the high dosages used in the University of Florida study can cause hallucinations and interfere with memory.
Flor found that prosthetic limbs can help amputees unlearn their aches. People fitted with prostheses that help them walk or pick up objects have less pain than those who use purely cosmetic replacements. Imaging studies show that with a functional prosthetic, the brain begins to respond as though the replacement limb were a part of the body. This semblance of normality dampens the errant pain signals.
Being Cruel to Be Kind: Don't Indulge Your Partner's Woes
A sympathetic partner may actually be an enemy in disguise, Flor and her colleagues found. Spouses who respond to a loved one's every flinch and moan can make pain worse. Constantly asking about the pain may interfere with the sufferer's efforts to distract herself.
Also, by giving special attention to suffering, partners may unintentionally reward the patient for his aches and discourage him from pursuing other activities. This isn't to say it's bad to help someone who's hurting—but in the case of chronic pain, diversion may be better than devotion. Flor works to change the habits of pain patients and their partners so that distraction and healthy behaviors such as exercising are rewarded.
Sex Is the Opiate of the Masses
Sex is nature's own pain reliever. Orgasm doubles the pain threshold, although the effect doesn't last long enough to serve as a treatment. Exploring this effect, Barry Komisaruk, professor of psychology at Rutgers University in New Jersey, has found that for women, just a bit of pressure in the vaginal region (not the clitoris) can dampen pain perception for hours. Research with rats suggests that rectal pressure in both sexes has a similar, but less powerful effect, possibly because both vagina and rectum use the same sensory nerve. Komisaruk and his students are studying women with chronic leg and pelvic pain to see if vaginal stimulation can help.
Why Women Don't Fear Pain—and Why Frightening Pain Hurts More
The stereotype that women are more sensitive turns out to be about half true. In response to pain, women initially report stronger sensations and higher anxiety than men do. As the hours go by, though, while women still say they hurt more, their anxiety decreases, whereas men's increases.
One theory is that the sensation has different connotations for men and women. Intense suffering is often a sign of life-threatening danger. But for women, the torment of childbirth is a normal, ultimately even joyful, experience. Perhaps women's lower anxiety in response to prolonged pain is because it may have this different "meaning." There are no data to prove this theory, but other experiments do clearly indicate that discomfort associated with danger hurts more. People who had their hands dipped in uncomfortably hot water were far less bothered by it when they had received a hypnotic suggestion referring to a tropical beach than when they had been led through a more frightening scenario.
Sloan-Kettering's Pasternak describes a patient who returned to him, years after surviving breast cancer, with unbearable lower-back pain. She assumed the cancer had returned and spread. When it turned out that she had a common disc problem—and no cancer—the woman no longer wanted pain medication. Says Pasternak: "Without the anxiety and fear of a recurrence, the pain was acceptable."
Drugs Don't Stop the Pain—They Help Us Ignore It
The most potent painkillers detach us from our suffering. Opioids such as morphine and Oxycontin, which mimic the brain's natural painkillers, not only dull the perception of pain but change our interpretation of it. In the cingulate, the drugs dampen emotional distress. Patients taking opioids often say that they still hurt, but it just doesn't bother them any more.
This ability to reduce both the unpleasantness and the sensation of pain makes these drugs indispensable, says Pasternak. Despite centuries and billions of dollars spent trying, no one has yet come up with better treatments.
Don't Tough It Out
Clint Eastwood might be able to ride across the desert with a bullet lodged in his arm, but for most of us, it's best to treat pain rather than suffer through it. Toughing it out could lead to long-term problems: Because it's difficult to "unlearn," chronic pain may be easier to prevent than to reverse. The longer and more intensely pain is felt, the more likely it is to become chronic. Many people resist pain medication, says McGill's Bushnell. "They say, 'I can stand it.' But you want to treat it as quickly and as completely as possible to reduce the chances of it becoming chronic."
Opioids have a reputation for abuse, but in truth, very few people who take pills for pain become addicted. Still, some doctors may be reluctant to prescribe high doses of painkillers, so you may need to be persistent to get the treatment you need.
Exercise May Work Out the Kinks
Exercise can be a painkiller. In research by Daniel Clauw and his colleagues at the University of Michigan, healthy college students who exercised regularly found that their feelings of pain and fatigue increased slightly when they quit for just one week. If healthy young people feel more pain when they don't work out, long-term inactivity may be even more harmful to anyone who is already hurting.
It's understandable that injuries and accidents often lead people to stop working out. But continuing to avoid exercise may make pain worse—and also interfere with mood and sleep. Beyond the psychological uplift of fitness, exercise may literally act as a painkiller by raising levels of important neurotransmitters such as dopamine.
Right now, insights into the psychological side of pain can only reduce, not eliminate, the need for drugs. But the growing understanding of how the brain's pain network connects with cognitive and emotional reactions provides promising insights. In combination with other kinds of treatment, psychological approaches may help to restore the pain system to its true purpose: alerting the body to danger rather than trapping the mind in agony.