The Body's Natural Painkillers

When I had my wisdom teeth removed my doctor told me to go home, rest and take a pill called codeine if I experienced any great pain.  I gladly followed his orders.  Had my doctor told me to go immediately to the gym and run on the treadmill until I felt better I would have looked at him like he was crazy and I doubt that I would have obeyed his commands.  While the two treatments for pain –codeine and exercise –seem to be opposites, recent neurobiological research suggests that a doctor would not be unjustified prescribing a hearty dose of physical activity to a patient suffering from pain.

When the body is subjected to a stress, such as a continuous workout at a level on intensity between moderate and high, a peptide is produced in the pituitary gland and hypothalamus is released into the central nervous system (1).  This peptide is an endogenous opiod biochemical compound, better known as an endorphin.  Notice that the scientific name of this compound has the root opioid, meaning that it belongs to the group of chemicals known to most people as opiates.  The use of opiates is stigmatized in our society because drugs such as heroin, methadone and morphine, which are highly addictive, are part of the opioid family.  Yet, the endorphins that are naturally produced in our bodies are of a very similar structure, and therefore have a similar function as the aforementioned drugs.  Swallowing a pill of codeine or injecting a hit of heroin fills the same opioid receptors in the brain that could be filled by participating in a rigorous workout.  These opioid receptors are most commonly found in the part of the brain responsible for integration and perception of pain and emotions.  Knowing the location of these receptors is useful in understanding the effects that opiates have on humans.  It also explains why some refer to endorphins as the body’s natural pain relievers.  While this information has shed light on some inquiries, it has also raises whole new set of questions:

If morphine and endorphins both act as painkillers, why not prescribe exercise?

            In the case of my sore mouth following the removal of my wisdom teeth, the answer to this question is fairly obvious.  While running would release the endorphins needed to soothe the pain, the act of running would also put my mouth at risk of being injured further.  This line of reasoning follows for any condition in which the risk of doing more injury outweighs the ameliorating effects of endorphin release.  However, a strict exercise regimen might be a better treatment for such conditions as chronic pain or depression.  Indeed, some of the leading medical research facilities such as the Mayo Clinic have begun to prescribe physical activity to patients battling chronic pain (3).  In 2007, the Mayo Clinic published research on the effectiveness treating symptoms of depression and anxiety with physical exercise.  Their findings suggest that 30 minutes of exercise a day for at least three to five days a week can significantly improve symptoms of depression (4).  While these findings are extremely recent, in 2001 the American Geriatric Society studied the effect of physical activity on osteoarthritis.  They concluded that moderate-level exercise does not exacerbate osteoarthritis pain nor accelerate the pathological process of osteoarthritis.  In fact, the study strongly suggested that increasing a patient’s level of activity would reduce pain and morbidity (5).  It seems that prescription of daily exercise is a promising alternative to highly addictive drugs currently used by many physicians.

  Why is it that so many people become addicted to heroin and painkilling medication, yet rarely develop an addiction to exercise?

            When physicians prescribe painkillers such as OxyContin, Vicodin and Percocet (all opiates) to alleviate pain, the patient often develops an addiction to the medication.  The same is true when people use opiates recreationally.  The mechanism of addiction is not completely understood by sceintists.  It is thought that upon experiencing the opiate, the brain becomes altered in such a way that causes an influx of extracellular dopamine in the nucleus accumbens, the part of the brain involved in reward and pleasure (6) (7).  Activity in this part of the brain may serves to explain the “high” euphoric feeling that accompanies ingestion of drugs, and that keeps users coming back for more.  While research has shown that levels of dopamine and serotonin increase in the blood during exercise (8), there seem to be far fewer cases of exercise addiction than heroin addiction.  Also, while many enjoy a good workout, few experience a “high”. 

            There are some people who claim to experience what is referred to as a “runner’s high”.  Accounts from people describing a runner’s high include the feelings of euphoria, a trance-like state, and the magical feeling of an out of body experience (9).  On some level, the experience sounds similar to a high one might encounter from taking drugs.  The people claiming to experience “highs” are typically those who consistently run long distances.  Perhaps the chemical changes that take place in the brain during light to moderate bouts of exercise are not drastic enough to produce the “high” sensation.  Heroin is able to quickly penetrate the brain, providing a quick, intense and effortless rush of pleasure which would help to explain why people are more likely to develop a heroin addiction than an exercise addiction. 

            Yet another possible explanation –a less neurologically based explanation –for the fact that more people experience a high from opiate drugs than from exercise, is that the sensation of “high” is socially constructed.  Howard Becker, a sociologist who studied marijuana users in the 1950s, suggested that three important events that needed to happen before a person could use marijuana for pleasure.  The person must learn the proper way to smoke (or otherwise ingest) the drug.  Then, the person must recognize the effects and attribute them to the drug.  Finally, and in this case most importantly, the person must learn to interpret the effects as a pleasurable “high” (10).  It is a socially accepted fact that shooting up heroin gets one high and that popping a couple Vicoden or codeine well make one feel good.  People hear about these experiences all of the time and accept them to be true.  The idea of experiencing a runner’s high is not commonly discussed, in fact, there is a debate about if such a thing even exists.  Perhaps people are going through the proper exercises, feeling the effects of the increased neurochemicals, but failing to recognize the sensations as a pleasurable high.

            The studies of addiction as well as the effects of physical exercise on the brain are both very hot topics in the world of scientific research.  Breakthroughs are being made almost daily in understanding the mechanism of addiction (7)(11).  Scientists and physicians are becoming more aware of the many benefits of tapping into our own natural supply of opiates –endorphins –and prescribing exercise and a healthy diet to patients suffering from chronic pain, depression, and even Alzheimer’s Disease and dementia (12).  Although it is not likely that a doctor will prescribe a 15 mile jog to a patient who has just had wisdom teeth removed anytime soon, perhaps this new information can help scientists find a way to “bottle human endorphins” or synthesize endorphins to create a potentially non-addictive painkiller.   

WWW Sources: 

(1) - http://en.wikipedia.org/wiki/Endorphin#Mechanism_of_action, Encyclopedia information about endorphins.

(2) - http://www.mayoclinic.com/health/chronic-pain/AR00017 , Mayo Clinic treats chronic pain with exercise.

(3) - http://www.mayoclinic.com/health/depression-and-exercise/MH00043 Mayo Clinic treats depression with exercise.

(4) - http://www.americangeriatrics.org/products/positionpapers/oae_guidelines.pdf, Common treatments for Osteoarthritis pain.   

(5) - http://en.wikipedia.org/wiki/Nucleus_accumbens, Encyclopedia information about the brain.

(6) - http://ajp.psychiatryonline.org/cgi/reprint/154/9/1195?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=progress+in+the+science+of+addiction&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT , Progress in the Science of Addiction.

(7) - http://borntoexplore.org/neurochem.htm, Brain Chemicals and Modern Life.

(8) - http://mysite.verizon.net/jim2wr/id80.html, a runner’s blog.

(9) - http://home.earthlink.net/~hsbecker/ Howie’s homepage.

(10) http://www.nytimes.com/2007/01/26/science/26brain.html?ex=1172638800&en=47f51f011f1608ef&ei=5070 , Brain Injury Halts Smoking…Key to Understanding Addiction.

(11) - http://neurology.health-cares.net/alzheimers-exercise-therapy.php, Exercise therapy for the treatment of Alzheimer’s and dementia.  

http://dianechesla.blogspot.com/2006/04/elusive-search-for-runners-high.html Very interesting blog regarding the East / West explanation of the runner’s high.