Uncertainty about future pain may delay recovery from disabling chronic pain

May 10, 2021

People suffering from chronic pain may go to great lengths to avoid potentially painful situations. (Unsplash/Adrian Swancar)

For the first time, researchers observed people avoiding certain body movements due to conditioned pain responses — a phenomenon known as generalized avoidance — extending our understanding of a fundamental principle in behavioral psychology and potentially informing future treatments of chronic pain. 

The study, carried out by psychologists at Maastricht University and the Catholic University of Leuven and published April 20 in The Journal of Pain, found that people who are less certain about when they will experience pain may be more likely to avoid potentially painful scenarios altogether, even opting to exert more effort to prevent the possibility of physical suffering.

The study was also among the first to show that healthy people can be made to adopt maladaptive behaviors when exposed to unpredictable levels and occurrences of pain. The findings may create new avenues for the treatment of chronic-pain patients, who make up roughly a fifth of the U.S. population.

Researchers hoped to explore the connections between pain and avoidance, because avoiding certain tasks or movements may worsen symptoms related to chronic pain disorders. Previous studies explored how the fear of pain might augment the severity of chronic pain, but few had considered how attempts to avoid painful situations might alter this relationship. 

"If you're afraid of a movement, but you still perform it, it means that you're not [technically] disabled. You're just experiencing discomfort because you're fearful," Eveliina Glogan, a researcher with Maastricht University and KU Leuven and the co-first author on the paper, told The Academic Times. "But when you actually start not performing those movements and activities — that's when it becomes a problem."

In many cases, pain acts as an adaptive sensation to help one detect health problems, the researchers explained, but in some chronic pain conditions, the brain may send pain signals even when there is no tissue damage or biological source. Patients may experience a reduction of symptoms through techniques such as cognitive behavioral therapy in conjunction with standard medical and biological interventions. 

Psychologists are still working to understand the underlying neurological mechanisms involved in avoidance behavior, which is when one stays away from a neutral stimulus due to the irrational fear that it could induce some degree of suffering. It's a feature of many psychiatric conditions, including social anxiety disorder and depression.

In this new study, a total of 134 healthy participants were asked to maneuver a digital ball on one side of an LCD screen toward an arch on the other side of the screen, using a robotic lever that provided real-time resistance to users. Volunteers had three options for reaching the desired location: an easy path with the least resistance, a medium path with moderate resistance and a difficult path with the highest degree of resistance.

In the first iteration of the experiment, the easiest option delivered a painful zap 100% of the time, while the medium option delivered a shock only 50% of the time. The most difficult option did not deliver a shock at all. A second experiment with a different group of people altered the rates of electroshock for the easiest and medium options to 80% and 40%, respectively, while the final, most difficult exertion option remained at 0%. The team made those changes to increase participants' uncertainty as to whether they would be shocked. Both groups then went through a generalization phase during which none of the three options delivered an electric shock.

The researchers wished to answer a key question: Would participants generalize the pain expectations from the first round of maneuvers and apply their avoidance tactics to the second, generalization round — and if so, for how long? In other words, the researchers wanted to find the point at which volunteers noticed that their prior experiences no longer applied to the current situation.

Those who had gone through the 50% and 100% shock-rate stages quickly learned the ropes, gaining a clear understanding of the risks involved in each option. And during the generalization phase, when none of the options delivered a shock, they rapidly unlearned their prior beliefs and adapted to the changing circumstances. Meanwhile, the participants from the second experiment felt more uncertain about which options delivered a shock and which did not, so they had more trouble challenging their previous assumptions during the generalization. Put simply, the researchers found that people with uncertain expectations about future pain may be less likely to learn or shift their understanding to accommodate new information.

In cases of chronic pain, people may limit their own bodily movements to accommodate their fear about future pain, such as avoiding bending down to pick up an object if that action previously caused pain. They may even develop unnatural body movements as a pain-avoidance technique, a concept that pioneering behavioral psychologist B.F. Skinner referred to as an "avoidance response." These responses can prompt a circular, self-fulfilling prophecy, in which more avoidance leads to even more fear about an activity, and a deeper belief that the activity or movement itself will lead to more pain in the future. 

Historically, most psychologists have believed that fear and avoidance are linearly intertwined: As someone grows more fearful of experiencing pain, they also begin to avoid that pain to a greater extent. But a newer wave of research has shown that this relationship is not always constant. Some people may find themselves engaging in a painful activity due to social stigma, curiosity or exploration.

Knowing the source of one's pain and recognizing its temporary nature can completely alter one's experience of it, Ann Meulders, an assistant professor at Maastricht University and the paper's senior author, told The Academic Times. "People who run a marathon might experience a lot of pain a day after or a few days after," Meulders said. "But it's experienced completely differently than when you experience pain out of the blue, and you don't know why it's happening."

The team thinks its study will contribute to a more robust understanding of the relationship between pain and avoidance, which can be used to develop more targeted treatments, such as psychoeducation that helps patients understand the complex mechanisms that may be leading to their pain. Researchers also hope to build trust with patients by reassuring them that their pain is real and should not be dismissed, even in the cases where that chronic pain is being generated by the brain itself rather than an external factor.

"Not everybody is aware that pain is not just a direct output," Meulders explained. "There's a lot happening on a top-down level when you experience pain. It comes in, but then a lot is happening [afterward]. The context is taken into account. Our emotions are taken into account. Our cognition and our beliefs about this pain that we are experiencing will help shape our experience."

The paper,"When do we not face our fears? Investigating the boundary conditions of costly pain-related avoidance generalization," published April 20 in The Journal of Pain, was authored by Eveliina Glogan, Kristof Vandael and Ann Meulders, Maastricht University and Catholic University of Leuven; and Rena Gatzounis, Maastricht University.

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