5 Surprising Facts About Pain

Impacted third molars, or wisdom teeth, can be very painful.
Impacted third molars, or wisdom teeth, can be very painful. (Image credit: Carlos Caetano | Shutterstock)

What Is Pain

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Pain is normal. About 75 million U.S. residents endure chronic or recurrent pain. Migraines plague 25 million of us. And one in six suffer arthritis.

The global pain industry pulls in more than $50 billion in drugs a year. Yet for chronic pain sufferers, over-the-counter pills are typically little help, whereas morphine and other narcotics can be addictive sedatives.

An overview study published in 2008 in the Journal of General Internal Medicine looked at multiple studies of pain and found "researchers don't yet know how to determine which [treatment] is best for individual patients." From studies of drugs to surgeries and alternative medicines, "We have found that there are huge gaps in our knowledge base," said Dr. Matthew J. Bair, assistant professor of medicine at the Indiana University School of Medicine.

Here's a look at six surprising facts about that achy sensation whose scientific understanding is painfully fuzzy.

Scientists don't understand pain

3d illustration of brain cells

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When you're in pain, you know it. But if scientists could fully grasp how pain works and why, they might be able to help you more. The American Academy of Pain Medicine defines pain as "an unpleasant sensation and emotional response to that sensation." More scientifically, pain is felt when electrical signals are sent from nerve endings to your brain, which in turn can release painkillers called endorphins and generate reactions that range from instant and physical to long-term and emotional.

Some pain is the result of an obvious injury. Other times, pain results from damaged nerves that are not so easy to pinpoint. "Pain is complex and defies our ability to establish a clear definition," said Kathryn Weiner, director of the American Academy of Pain Management. "Pain is far more than neural transmission and sensory transduction. Pain is a complex mixture of emotions, culture, experience, spirit and sensation."

Pain may shrink the brain


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If you have chronic pain, you know how demoralizing and debilitating it can be, physically and mentally. It can prevent a person from completing routine activities and skyrockets one's irritability for reasons "others" don't quite understand.

But that's only half of the story. The brains of people with chronic backaches are as much as 11 percent smaller than those of non-sufferers, scientists reported in 2004. Scientists aren't sure why. "It is possible it's just the stress of having to live with the condition," said study leader A. Vania Apkarian of Northwestern University. "The neurons become overactive or tired of the activity."

Painful migraines and sex go hand-in-hand

Man and woman in bed.

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It may not eliminate the phrase "Not tonight, honey ..." but a 2006 study found that migraine sufferers had levels of sexual desire 20 percent higher than those suffering from tension headaches. The finding suggests sexual desire and migraines might be influenced by the same brain chemical, and getting a better handle on the link could lead to better treatments, at least for the pain portion of the equation.

Women feel more pain

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Any man who has watched a woman having a baby without using drugs would swear that women could tolerate anything. But the truth is, guys, it hurts more than you can imagine. Women have more nerve receptors than men. As an example, women have 34 nerve fibers per square centimeter of facial skin, whereas men average just 17. And in a 2005 study, women were found to report more pain throughout their lifetimes and, compared with men, they feel pain in more areas of the body and for longer durations.

Some animals don't feel our pain

naked mole rat

(Image credit: Rochelle Buffenstein/City College of New York.)

Animal research could offer clues to eventually relieve human suffering. Take the naked mole rat, a hairless and nearly blind subterranean creature. A 2008 study detailed in the journal PLOS Biology found it feels neither the pain of acid nor the sting of chili peppers. If researchers can figure out why, they might be on the road to new sorts of painkilling therapies for humans.

In 2006, scientists found a pathway for the transmission of chronic pain in rats that they hope will translate into better understanding of human chronic pain. Lobsters feel no pain, even when boiled, scientists said in a 2005 report that is just one more salvo in a long-running debate.

Live Science Staff
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