Have you ever noticed how aches and pains seem to fade when your adrenaline is really pumping? Or have you ever felt pain deep in your gut after a tragedy? If so, you've already discovered that pain -- like so many other things in life -- is deeply sensitive to stress.
When you're under stress -- brief or lingering, mild or severe -- your body releases chemicals that change the way your brain senses pain. In some cases, stress actually eases pain. A strange sound in a dark alley can make you forget about your aching knee, a handy thing if you decide to run. But in other cases, the body's response to stress can fuel chronic pain that serves no purpose.
In recent years, scientists have made great progress in uncovering the links between stress and pain. Each discovery sheds new light on the amazing workings of the brain. More important, the research may soon open up new avenues for pain relief.
Natural pain relievers
In the short term, stress can be a powerful painkiller. When the brain senses a serious threat or a traumatic injury, it releases a veritable pharmacy of chemicals to quickly dampen the pain. Called "stress-induced analgesia," this reaction explains why people often don't feel pain immediately following an injury. It enables a soldier in battle -- or, for that matter, a deer trying to outrun a mountain lion after escaping from its claws -- to focus on survival rather than pain. Some soldiers hit by enemy fire don't even realize that they've been injured until the battle is over.
Interestingly, the painkillers released by the body during stress are very similar to chemicals found in illicit drugs. In addition to blocking pain, these chemicals trigger the release of dopamine, a compound that provides feelings of pleasure.
In 2005, researchers discovered that stress can also trigger the release of marijuana-like compounds called cannabinoids. The study, published in Nature, found that the body's version of marijuana is highly effective at blocking out pain. As reported by the University of Georgia, researchers hope the discovery can lead to new medications that can relieve pain without the side effects of either narcotics or "real" marijuana.
Lingering stress, chronic pain
Though the body is well-equipped to block out pain during fleeting moments of stress, its response to long-lasting stress isn't nearly so helpful. The brain can't keep pumping out opioids forever, and the supply eventually runs out. To make things worse, stress also damages the brain's ability to produce dopamine, the pleasure compound stimulated by opioids. In short, chronic stress can short-circuit the brain's normal response to adversity.
For some people, this chemical upheaval can set the stage for chronic pain. According to a report in Medical Hypotheses, stress-induced damage to the body's dopamine-producing mechanism may contribute to the onset of fibromyalgia. People with this condition are extremely sensitive to pain and often have unexplained pain in trigger points throughout their body. Fibromyalgia could be an exception to a basic rule of stress-related diseases. Heart disease, hypertension, depression, and other diseases can get their start when the body produces an overload of stress hormones. Fibromyalgia may be just the opposite: As reported in Arthritis Research and Therapy, some studies -- but not all -- have found that people with fibromyalgia tend to have unusually low levels of cortisol, a hormone that the body releases in times of stress. The lack of cortisol may be a sign that body isn't responding to stress -- or fighting pain -- the way it should.
More ways stress hurts
Despite the body's best efforts at self-medication, stress can sometimes be the cause of pain. For example, a bad day at work may bring on a tension headache. Stress is also a common trigger for migraines.
And, as many people can attest, stress is hard on the digestive system. As reported the journal Gut, stress compounds -- especially one called CRF -- can make the intestines extra sensitive to pain. Some experts believe that this sensitivity plays a large role in irritable bowel syndrome, a sometimes painful condition that is highly reactive to stress. Researchers are currently investigating drugs that block CRF as potential treatments for the syndrome.
Fear and anxiety can also fuel pain. As Robert Sapolsky writes in his book Why Zebras Don't Get Ulcers (Henry Holt and Co., 2004), the mere sight of a hypodermic needle can be enough make a person's arm throb. In this case, the brain's emotions overwhelm its natural painkillers. The more a person fixates on pain -- existing or expected -- the more it hurts.
While scientists still have much to learn about stress and pain, one thing is already clear: For many people, relaxation can be a powerful pain reliever. Even the venerable Mayo Clinic suggests meditation as a potential remedy for chronic pain. Likewise, people with irritable bowel syndrome, fibromyalgia, or chronic headaches may find relief if they can reduce stress in their lives or change their attitudes about life's problems. If you have one of these conditions, cognitive behavioral therapy or another type of counseling could become an important part of your recovery.
Harris, L.A. et al. Irritable bowel syndrome: New and emerging therapies. Current Opinion in Gastroenterology.
McBeth, J. et al. Hypothalamic-pituitary-adrenal stress axis function and the relationship with chronic widespread pain and its antecedents. Arthritis Research and Therapy 7: R992-R1000.
Sapolsky, R.M. Why Zebras Don't Get Ulcers. Third Edition. Henry Holt and Co. New York. 2004.
Wood, P.B. Stress and dopamine: implications for the pathophysiology of chronic widespread pain. Medical Hypotheses 62(3): 420-424.
Hohmann, A.G. et al. An endocannabinoid mechanism for stress-induced analgesia. Nature. June 23, 2005. 435(7045): 1108-1112
University of Georgia. Scientists discover the body's marijuana-like compounds are crucial for stress-induced pain relief. http://www.eurekalert.org/pub_releases/2005-06/uog-sdt062005.php
Mertz, H. Role of the brain and sensory pathways in gastrointestinal sensory disorders in humans. Gut 51:i29-i33.
Mayo Clinic. Meditation: Focusing your mind to achieve stress reduction. http://www.mayoclinic.com/health/meditation/HQ01070
American Association for the Treatment of Opioid Dependence. Neurobiology of heroin addiction and of methadone treatment. http://www.aatod.org/1998-3.html
Mayo Clinic. Tension headache. http://www.mayoclinic.com/health/tension-headache/DS00304
The National Womens Health Information Center. Migraine headaches. http://www.4woman.gov/faq/migraine.htm
UCLA Center for Neurovisceral Sciences and Womens Health. Altered stress responses in irritable bowel syndrome. http://www.cns.med.ucla.edu/
National Institute of Mental Health. Depression can break your heart. http://www.nimh.nih.gov/publicat/heartbreak.cfm
Goldenberg, D.L. Update on the treatment of fibromyalgia. Bulletin on the Rheumatic Diseases. http://www.arthritis.org/research/Bulletin/Vol53No1/References.asp