The Experience of Chronic Pain: Many Dimensions, Lots of Uniqueness

At the 2019 North American Pain School, psychologist and pain researcher Robert Edwards focused on how psychological factors contribute to chronic pain. Image credit: Daniil Peshkov/123RF Stock Photo.

Editor’s Note: The fourth North American Pain School (NAPS) took place June 23-28, 2019, in Montebello, Quebec, Canada. This educational initiative brought together leading experts in pain research and management to provide 30 trainees—part of the up-and-coming generation of pain researchers—with scientific education, professional development and networking experiences. 

Six of the trainees were also selected to provide first-hand reporting from the event, including summaries of talks presented at the meeting. Here, Sarasa Tohyama, a PhD student at the University of Toronto, Canada, summarizes a talk delivered by Robert Edwards, a psychologist and pain researcher at the Brigham and Women’s Hospital Pain Management Center in the Boston area. Edwards discussed the biopsychosocial model of pain and how psychological aspects such as catastrophizing contribute to the pain experience.

Pain is a multidimensional experience in which biological, psychological and social factors all play an important role—this is known as the biopsychosocial model of pain. There is also tremendous individual variability in how people perceive pain and how pain affects them. For example, two individuals who have the same injury may differ in how much pain they report and how well they function. So where does one even start in understanding how pain arises?

At the 2019 North American Pain School, Robert Edwards, a clinical psychologist and pain researcher at Brigham and Women’s Hospital Pain Management Center in the Boston area, shared insights into the many-faceted nature of pain. In particular, he discussed the biopsychosocial model of pain, with a special emphasis on key psychological factors such as catastrophizing.

The message of his talk was that a better understanding of how chronic pain comes about is emerging from a plethora of studies in the field of pain psychology. The picture taking shape is that the “psycho” is as important as the “bio” and “social” in the biopsychosocial model of pain. And, increased knowledge of pain psychology is helping to identify risk factors for chronic pain, which could one day speed the path towards personalized pain medicine.

The biopsychosocial model of pain and catastrophizing
While there is no one universally agreed upon biopsychosocial model of pain, typical descriptions of this model include biological factors such as nerve injury and inflammation, psychological components such as mood and anxiety, and social elements like relationships with family and friends, among many others. All of these factors can interact as well. For example, a person can experience pain from a physical injury such as a broken arm, but the pain can also be influenced by the person’s level of anxiety and whether they have social support.

One of the factors in the biopsychosocial model that Edwards is specifically interested in is a psychological component called pain catastrophizing. This is a negative set of cognitive and emotional responses to pain, involving the tendency to magnify the pain experience, ruminate on it, and feel helpless. Psychologists use a measure called the Pain Catastrophizing Scale (PCS) to measure catastrophizing in people who have pain.

Before going any further, it’s important to note that while catastrophizing has been studied extensively by pain researchers and there is now a large body of research to support its importance in the experience of pain, significant controversy has developed in recent years over the term itself. One of the most significant issues is that patients may feel they are being blamed for their pain when they are told they are catastrophizers. Edwards participated in a recent interview with 2019 North American Pain School patient partner Billie Jo Bogden, where they discussed this issue and the importance of how to discuss psychosocial factors in a non-pejorative manner.

“Terms like catastrophizing are not ideal for communicating what we want to study in a nonjudgmental way,” Edwards said during the interview. “Pain is, generally, an extremely stressful and unpleasant experience for everyone, but each person is unique in how he or she experiences pain. Pain catastrophizing refers to experiencing pain as highly distressing, attention grabbing, and paralyzing―more threatening and out of control than what others with the same pain might experience. We should be communicating that some factors might be best addressed with physical treatment and some might best be addressed in the psychosocial realm. We need to get to a point where we can identify those things nonjudgmentally and nonpejoratively, and figure out how best to help people in those areas.”

What does the research say?
There are now a large number of studies showing that high levels of catastrophizing are a risk factor for the later development of chronic pain. And, if a person has chronic pain, high levels of catastrophizing are also a risk factor for relatively poor treatment outcomes.

For example, in a study published in 2014, researchers at the University of Calgary looked at 58 patients with peripheral neuropathy (pain caused by damage to nerves outside of the brain and spinal cord). This study found that in those with higher levels of catastrophizing, certain drugs were less effective for the pain. These patients also showed greater impairments in their quality of life.

More recently, in 2017, Edwards’s group published a study in the journal PAIN Reports that monitored 200 chronic pain patients, over a period of six months, who were taking opioids to manage their pain. Results showed that patients who catastrophized a lot (“high catastrophizers”) reported much higher levels of side effects from their opioid medications.

Catastrophizing might also interfere with other treatments for pain, including non-drug treatments. For example, Edwards’ group recently did a study in patients who had arthritis pain in their knees. The researchers looked at a variety of factors including daily levels of pain intensity, physical activity, and catastrophizing. The study, published earlier this year in the journal Pain Medicine, showed that for the days when patients reported high levels of physical activity, high catastrophizers reported much greater levels of pain, compared to low catastrophizers. This suggests that catastrophizing might make it difficult for people with pain to engage fully with physical therapy and to use exercise to manage their pain.

Catastrophizing and pain sensitivity
There is a whole lot that goes along with catastrophizing. For example, higher levels of catastrophizing are associated with elevations in pain sensitivity, which is also a risk factor for the development of chronic pain.

For example, in a recently published study by Edwards’ group in the journal PAIN, patients with chronic low back pain showed higher levels of pain sensitivity relative to people without pain. Here, pain was assessed using a method called quantitative sensory testing, which measures how much pain a patient reports in response to heat, cold or a pinprick, for instance. This difference in pain sensitivity was also associated with increased catastrophizing.

Catastrophizing is also associated with enhanced temporal summation, a phenomenon where, over time, people report increased pain in response to a repetitive painful stimulus. For example, a pinprick applied to the finger may be perceived as more painful after the tenth time a person experiences it, compared to the first time. Several studies have shown that people with chronic pain who show higher levels of catastrophizing also have enhanced temporal summation. So, here too, the research links catastrophizing to a heightened sensitivity to pain.

Looking into the brain
Brain imaging has emerged as a critical tool to learn more about pain. New imaging techniques allow researchers to examine the structure as well as the function of the brain, and how certain brain regions or networks of brain regions communicate with one another during pain.

In particular, studies using functional magnetic resonance imaging (fMRI), which measures brain activity by detecting changes in blood flow that occur when neurons become more active, show that chronic pain patients have altered brain networks. These networks include the sensorimotor, salience, and default mode network.

The sensorimotor network refers to brain areas that are activated during sensory and/or motor tasks, such as tapping a finger. The salience network is a collection of brain regions involved in detecting and filtering salient stimuli—things that capture our attention. The default mode network is commonly active when a person is not focused on the outside world, such as during a daydream or when the mind wanders.

In healthy adults, these brain networks are generally separate and do not overlap with one another. Edwards is interested in whether catastrophizing and other psychosocial factors that accompany pain, such as depression, contribute to a blurring or overlap of brain networks in chronic pain.

To learn more, in collaboration with researchers at Massachusetts General Hospital in Boston, Edwards’ group decided to look at people with fibromyalgia. Fibromyalgia is often considered the quintessential biopsychosocial chronic pain disorder. This is because people with fibromyalgia not only report pain and tenderness throughout the body, but also many other symptoms like fatigue, poor sleep, and fuzzy thinking. As such, fibromyalgia is a condition where it is particularly valuable to study the interplay of pain and psychosocial factors—catastrophizing in particular.

In their study, Edwards and colleagues found a large overlap between the sensorimotor and salience networks in patients with fibromyalgia, whereas healthy people without pain did not show this overlap. And, these changes correlated with pain intensity, pain catastrophizing, and temporal summation.

In addition to having patients lie in a brain scanner at rest, researchers can also have them complete specific cognitive tasks, such as a pain catastrophizing task, while in the scanner. This gives those who study pain an even better understanding of what’s going on in the brain during painful conditions.

For example, Edwards’s group designed an fMRI study where they placed fibromyalgia patients in a scanner and asked them to either reflect on written catastrophizing statements (in particular, to reflect on how these catastrophizing statements mirrored their own experience of pain) or on neutral statements. When patients reflected on the catastrophizing statements, there was greater activation in brain areas that are part of the default mode network, compared to when they reflected on the neutral statements. And, the greater the brain activation while considering the catastrophizing statements, the higher the patients’ daily pain and levels of catastrophizing.

A path to personalized pain medicine
Edwards’ talk showed that psychological factors such as catastrophizing can play an important role in the pain experience, and this is reflected in changes in the structure and function of the brain. These factors interact with biological and social factors, all of which shape the multidimensional experience of pain, which is unique to each person.

So what does it all mean for people with chronic pain?

The new understanding of pain psychology could have important treatment implications down the road, according to Edwards. He said that the growing number of studies on risk factors for chronic pain such as catastrophizing, along with work uncovering what happens in the nervous system in different pain conditions, speeds the path to tailoring pain treatments to the unique characteristics of each person—often referred to as personalized medicine.

Here, timing is important: researchers are hoping to identify the risk factors for chronic pain as early as possible. This will help in choosing the treatment that is most likely to be effective, with the fewest negative side effects, for each individual patient.

PRF Correspondent Sarasa Tohyama is a PhD student at the University of Toronto, Canada.