May 19th, 2011
For those who develop chronic pain, the experience is life changing to say the least. Suffering from unrelenting pain every hour of the day is draining and will often cause drastic reductions in quality of life. Among those afflicted with such sustained suffering, the effects of the pain frequently intrude into many aspects of daily living. That said, for the most part, these effects of chronic pain are something of which most people are aware.
Where general awareness is far less, however, is with respect to the effects of chronic pain on the body. In particular, chronic pain changes the way that the brain works. This means that untreated or under treated chronic pain exposes patients to more than just levels of discomfort. Poorly treated long term pain leads to a form of brain injury in patients. This suggests that physicians have a greater responsibility in taking steps to reduce the pain that their patients experience.
Throughout evolution, pain has served an important role in self-preservation. A feeling of pain tells us when we have been hurt so that we can ideally change the activities in which are we are involved. But, when pain becomes chronic, it no longer serves its primitive role in prompting a fight or flight response. Indeed, in modern society, where most individuals are distanced from threats of physical injury, chronic pain is a significant contributor to unnecessary suffering.
Who Suffers from Chronic Pain?
Within the population, this results in roughly 20 to 25% of people living with chronic pain. In the US, low back pain, the most common form of chronic pain, affects between 24 and 30% of the population.
Because this form of chronic pain is so common, scientists have conducted considerable research on the topic. What the research has revealed over the last two decades is the way in which the presence of chronic pain alters the brain.
How Does The Brain Changes In Response To Chronic Pain?
Research from Northwestern University in 2008 determined that the brain activity in patients with chronic pain is different from those who do not suffer ongoing pain. Specifically, the researchers observed that a front area of the brain largely associated with emotion is constantly active in people suffering with chronic pain. This contrasts with the normal activity of the brain where changing activities and thoughts cause different areas of the brain to become active while other areas become less active.
The researchers believe that the result of this excessive activity is that the brain nerve cells or neurons in the specific overactive region of the brain wear out and die prematurely. These nerve cells are described as gray matter and researchers have, in the past, observed lower numbers of these cells in the brains of those suffering from chronic pain. In one study, the research recorded as much as an 11% reduction in the overall size of the brain in those suffering from such ongoing pain. This sort of reduction in brain material typically takes place over 1 or 2 decades in healthy individuals.
In addition to the changes in gray matter, the constant nerve activity and firing of these nerves also causes the nerves involved in communication to rewire in ways that are very different than in a normal brain. These nerve cells are the brain’s white matter or “cabling” and they tend to form more complex wiring patterns for chronic pain sufferers. In particular, they form more links between the parts of the brain that process pain, stress and emotions.
Lastly, the changes in brain activity in chronic pain sufferers also affect the area of the brain responsible for directing sensory stimulation. The cells in this area become less used and atrophy over time causing this area of the brain to shrink.
How Does Chronic Pain Change Behavior?
Now, it is one thing to talk about changes in the brain, but what most of us will find important is how brain changes affect behavior and personality. Previous research has found a number of changes in mental function caused by chronic pain. One example is that those suffering from chronic pain have difficulty making even simple decisions and interacting with other people.
This finding makes sense because of the over activity of those specific areas of the brain involved in processing pain. Essentially, because of the constant internal brain stimulation, a person in chronic pain is impaired in a similar manner to those who are trying to multitask. Too many things happening in the brain at once makes concentration difficult.
Another common problem amongst people with chronic pain is an inability to sleep. Of course, any feeling of pain will certainly make it hard to sleep, but other brain changes also contribute to sleeplessness. In particular the area of the brain responsible for sensory stimulation is also responsible for controlling our wake and sleep cycle. When this area of the brain atrophies and shrinks, individuals have both difficulty sleeping and additional difficulties in maintaining alertness.
In addition to these symptoms, yet another symptom frequently experienced by those in chronic pain is anxiety. Based on research from the University of California, researchers observed that patients in chronic pain have reduced brain activity in the areas of the brain that control the human response to pain. The researchers believe that the reduced control over pain signals causes the brain in these individuals to become extremely vigilant in anticipating future pain. If this is true, it helps explain the heightened levels of anxiety frequently experienced by suffering from chronic pain.
The final symptom that has a significant effect on those suffering from enduring pain is depression. In the same study at the University of California, the research results led the investigators to believe that reduced pain control in the brain and the complex brain wiring changes causes increased emotional reaction to future experiences of pain and discomfort. They suggest that this explains why those with chronic pain are often resistant to treatment.
Essentially, the changes in their brain contribute to a sense of hopelessness in being able to overcome the pain.
These results are important because they agree with other research that has found that people suffering from depression have reduced ability to control their emotional state. It also supports studies that have identified that 30 to 60% of patients with chronic pain also develop depression.
Undoing The Brain Changes When Chronic Pain Ends
While the news so far is certainly not positive for people suffering from chronic pain, recent research does have some positive news to offer. Researchers at McGill University found that chronic pain patients who were eventually treated for their pain were able to recover. They found that the brains of these individuals began to increase in mass to levels that were normal. The area of the brain responsible for controlling pain also repaired itself and began to operate normally. Lastly, the number of gray matter cells also increased.
Most importantly, mental abilities returned to normal levels with these patients being able to again perform tasks requiring mental focus.
Although we are largely familiar with the reductions in quality of life that accompany chronic pain, our understanding of the effects of pain on the brain has not been good. Chronic pain is debilitating both physically and mentally, causing damage to our brains and mental abilities. Many of the changes to the brain can subsequently make coping with the pain even more difficult. As a result, physicians need to make greater efforts in treating the chronic pain that patients experience. We now know that failing to do so becomes a failure to live up to the intent of the Hippocratic oath in “doing no harm”.