Why do people seek medical care? The most common reason is pain. But what is pain, and what causes it? There are many question surrounding this charged topic, especially with the epidemic of opioid addiction, with the heartache, financial ruin and death that is associated. These are questions that continue to plague modern medicine, and human existence in general, understandable when you consider that over one-third of the world’s population suffers from persistent or recurrent pain, costing the American public approximately $100 billion each year in health care, compensation, and litigation.

Chronic pain is associated with many, varied conditions, including such favorites as a back injury, migraine headaches, arthritis, diabetic neuropathy, and cancer. Many of the currently available pain therapies are either inadequate or cause uncomfortable or deleterious side effects. Chronic pain results not just from the physical insult but also from a combination of physical, emotional, psychological, and social abnormalities. Although people think of pain as a response to an injury, it is a complex phenomenon. Pain is both a sensory and an emotional experience that is felt differently by everybody. What’s more, there is a difference between how you are confronted with pain and how you go on to tolerate it. While the terms “pain threshold” and “pain tolerance” are commonly used and interchanged, these two terms are very different. Pain threshold defines the level at which we feel a stimulus as being painful, but pain tolerance has a very different meaning; it defines how much a person can take some level of pain without breaking down. Still, most will agree that chronic pain is a tremendous problem in our culture, where people usually live well into their 70’s and beyond, suffering from various degrees of age-related joint problems.

The 21st century has been an incredibly exciting time in pain biology. New information in basic pain research is virtually exploding onto the scene, and has revealed many new targets for unique pain therapies.

Major advances have occurred on many fronts, from molecular studies that have identified special proteins in pain receptor nerves, to imaging studies of the brain which reveal how pain is experienced on a cognitive level.

The research is on-going, but significant breakthroughs in pain control have not yet reached the marketplace. Many are anticipating the day when beneficial options for chronic pain will be available.

One of the most difficult aspects of treating pain has been the uncertainty associated with patients’ self-reports of pain. How accurate are these reports? We recognize that pain is obviously a very individual thing, reported differently, described differently, from person to person. We all know someone who seems very sensitive to pain, as well as those who appear to tolerate pain very well. Until recently, there was no objective evidence that could confirm individual differences in pain sensitivity.

A new study utilized the marvelous powers of the MRI to assess brain function. The results revealed that participants who described an intense pain from a specific stimulus had greater activation of specific regions of the brain, primarily those important in pain. In contrast, people who said that the same stimulus was only mildly painful had minimal activation of these areas. The findings from these and other studies indicate that self-reports of pain intensity can be correlated to brain activity.

An important conclusion is that self-reports of pain should indeed guide treatment. Another important finding indicates that incoming painful information is processed by the spinal cord in a generally similar manner person to person. Yet, the experience becomes very different from one individual to the next once the brain gets involved.

Many factors have been found to be important in the variability of pain perception, including the most predictable of them: genetics. All the bits and pieces of the nervous system are built from instructions in the genetic code, which varies slightly from person to person. Another consideration is age. Pain can be very different in infancy than in old age.

Until the last two decades of the 20th century, it was thought that babies didn’t feel pain. Infants were not given anesthesia during surgery because doctors considered it unnecessary for pain control and because they feared a potentially lethal anesthesia overdose. Medical opinion has since reversed. Not only do infants experience pain, but the pain they experience early on can influence their perception of pain as they get older. More pain early on means a higher sensitivity to pain later.

Mood is also influential. There is widespread agreement that depression lowers pain tolerance. And that doesn’t just go for the truly depressed: making people temporarily unhappy by showing them sad photographs also increases pain sensitivity. People who are anxious about pain become more pain-sensitive in the situations that evoke their pain-related anxiety. Researchers speculate that chemicals in the brain may be involved in both mood and pain perception. But the exact link between pain and depression remains unclear

Neuropathic pain is a whole other animal. This is the pain generated by a nerve problem, be it from disease or injury to a nerve. This type of pain is insensitive to morphine as well as other opioid drugs, and is currently best managed with antidepressants and antiepileptics. Despite advances in understanding the complex neurobiology of pain, the pharmacological management of these pain syndromes remains insufficient. Unfortunately, several promising drugs for these conditions have failed in late-stage development.

Still, opioids remain the most powerful medications for relief of acute pain (with a common example being post-operative pain). This ubiquitous class of pharmaceuticals, typically quite effective at the treatment of acute pain, are prescribed all too often for chronic conditions.

The classic representative of this group is morphine, which has its effect through its action on the receptors that inhibit pain signals. Although ineffective at handling neuropathic pain, they remain too frequently prescribed for this type of problem.

Some non-pharmacologic methods of pain control include the use of electrical nerve stimulation, known as TENS, in which an electrical signal is applied to fool the nerves carrying pain information. Another very different method is with acupuncture, though how this technique works to reduce pain is largely unknown.

A variety of mind-body therapies have been used over the years. These may be thought of as pain coping techniques since the pain is still experienced, but the power of the mind is used to alter perception of the noxious sensation. For some, these methods can be quite effective, but results vary since this mind-body connection varies so greatly amongst different individuals.

Many options exist for dealing with chronic pain, other than using narcotic pain medication. Some are more effective than others, with the benefits of some clearly dependent on the psychology of the individual. The reason why some people are more sensitive than others comes down to how our body handles pain, from the skin to the brain and the structure of the brain itself.

But clearly it is altered by many factors, including how we think about pain, and deal with pain, on an emotional level. As mentioned, chronic pain is a tremendous problem, but if the source of your pain can be adequately resolved, you will clearly be better off. Research is on-going, but effective answers to the treatment of chronic pain have yet to be found.

Editor’s note: Dr. Conway McLean is a podiatric physician now practicing foot and ankle medicine in the Upper Peninsula, having assumed the practice of Dr. Ken Tabor. McLean has lectured internationally on surgery and wound care, and is board certified in both, with a sub-specialty in foot orthotic therapy. Dr. McLean welcomes questions, comments and suggestions at drcmclean@penmed.com.