New Research Helps Us Better Understand the Complexity of Pain

Zachary Walston
dragana991 from Getty Images

I often wished that more people understood the invisible side of things. Even the people who seemed to understand, didn’t really.”
― Jennifer Starzec, Determination

Our minds are powerful. Our thoughts and expectations shape our future experiences. As we learn more about pain, we have come to understand the experience of pain is complex.

Common beliefs are routinely debunked. For example, mounds of research show there is no ideal posture and rounded necks and back are not dangerous.

I fight the misguided narratives around pain daily as a physical therapist. Whether I am educating patients in the clinic, clinicians in the classroom, or the general population through writing, I fall back on the research, not biased anecdotes.

Instead of throwing a bunch of hard science at you, I thought I would take a different route and show some interesting studies that demonstrate how complex pain is.

It took a couple of years for me to drop my outdated mindsets and embrace the research. I hope these studies set you along the same path.

#1 — It’s hard to predict pain

This review — a research paper pulling many studies on a single topic — showcases the difficulty of predicting pain.

Many factors influence the pain experience. Pain predictions also change with knowledge of results. Some patients will overpredict pain before a task initially, especially if they are fearful of the task, and once they realize they overpredicted, they underpredict subsequent ratings.

Greater variability is seen in patients with high anxiety compared to low anxiety. Patients with high anxiety overpredicted pain after multiple treatments but the accuracy improved.

Other studies show increases in future pain prediction when underpredicting an initial unknown response (healthy subjects given electric shocks). The spontaneous mismatch and underprediction lead to increased fear of future shocks and subsequent over predictions. The simple act of a clinician or researcher asking a patient their pain rating can influence the outcomes of an intervention.

This ties into the poor reliability of current pain ratings, not just future ones.

The reliability of pain reports is questionable. Descriptors and locations are variable and provide poor diagnostic utility, particularly in chronic pain. That does not mean reports of pain are useless, but they are incomplete and potentially misleading.

#2 — Chronic pain is rarely localized

One study assessing self-reported musculoskeletal pain showed that reporting a single pain site or none at all is rare; nearly two out of five individuals reported pain from at least five sites. There is a strong and linear relationship between the number of pain sites and functional ability. The number of pain sites is a strong predictor for future disability, up to 14 years later.

It is common for patients in healthcare settings to report other symptoms in addition to pain. A recent research study assessed the relationship between self-reported non-musculoskeletal symptoms and musculoskeletal pain.

Study participants were asked to report whether they had experienced pain or discomfort in any of ten different body regions during the last 7 days:

  • Head
  • Neck
  • Shoulder
  • Elbow
  • Hand/wrist
  • Upper back
  • Lower back
  • Hip
  • Knee
  • Ankle and foot.

They were asked to report non-musculoskeletal symptoms as well. They included palpitations/extra heartbeats, chest pain, breathing difficulties, heartburn, stomach discomfort, diarrhea, constipation, eczema, tiredness, dizziness, anxiety, depression, and sleep problems.

A simple correlation analysis showed a strong association between non-musculoskeletal symptoms and the number of pain sites. Basically, as the number of pain sites increase, the number of non-pain symptoms increases as well.

#3 — Medical tests are easily biased

Patients and providers have expectations going into a check-up or treatment session. They have expectations about the experience and predictions about the results of tests and treatments. Those expectations change throughout the encounter as new information is gathered, including education about the body.

In this study, the researchers induced a pain response by injecting 15 participants with intramuscular hypertonic saline infusion in the thenar muscles. All of the participants received identical background information regarding basic median nerve biomechanics and basic concepts of differential diagnosis via mechanical loading of painful structures. The next block on information differed.

One group was told the origin of their induced pain was muscular and the other group was informed it was nerve-based. Basic pathologic explanations were provided to support these notions. After all of the education was provided, each participant was evaluated in the five different positions of the median nerve neurodynamic test and asked to provide a pain rating.

The ‘muscle pain’ group reported no changes in pain throughout the test, while the pain intensity and size of the painful area increased and decreased in the ‘nerve pain’ group consistent with their expectations and the level of mechanical nerve loading.

This research highlights the power of expectations and their influence on the pain experience. Verbal information is just one source of setting expectations, however.

#4 — Provider facial expressions change pain expectations

Research has shown nonverbal and verbal behaviors can have placebo or nocebo effects on a patient’s outcomes. Providers can change a patient’s pain and the success of their interventions through specific communication strategies such as smiling, dressing professionally, conveying confidence, and maintaining frequent eye contact.

A recent study narrowed their focus, assessing the influence of first impressions on treatment choices and expectations.

The paper includes five studies totaling 1108 participants. In four studies, participants were shown computer-generated faces while in the fifth they saw real faces. Participants were asked questions such as, “which medical provider do you prefer?” when comparing two images. The researchers assessed how the competence measures influence potential pain perception and analgesic use.

Participants chose providers they believed appeared more competent. They also expected procedures to be less painful, requiring less analgesic use, if treated by the preferred providers.

#5 — Food insecurity increases chronic pain prevalence

Food insecurity can be defined as inadequate or insecure access to food due to financial constraints. It is associated with chronic pain and prescription opioids use. As we become more comfortable integrating nutrition conversations into our clinical practice, we have to consider the potential influence of food insecurity.

Food insecurity in the US has hovered between 11 and 15% over the past twenty years. While the exact numbers are not known, it has spiked during the pandemic. If you work in a low-socioeconomic area or a food desert, the rates will be even higher.

Providers need to consider food insecurity as it can influence nutrition conversations. If providers are unaware of a patient’s food security, they may unknowingly induce shame through their education. This can fracture the patient-provider relationship. Outside of nutrition conversations, food insecurity can impact a patient’s presentation and pain experience.

Research shows, food-insecure people are more likely to experience severe pain which causes activity limitation. Food insecurity predicts intensive, excess, and alternative use of prescription opioids. Food insecurity is also a more powerful predictor of pain and prescription opioids use than income.

Pain is complex

These are only a handful of studies highlighting the complexity of pain. Pain research is growing daily but our biases are hard to overcome. Whenever you hear or read a claim about pain, determine the source and credibility. Once you do some digging, you will find most claims lack support.

It’s disturbing, as chronic pain costs our healthcare system billions of dollars annually. I routinely see people in pain who underwent unnecessary procedures and bought products based on health misinformation. The only way anything will change is to challenge the current narrative and do the homework.

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I am a physical therapist, researcher, and educator whose mission is to challenge health misinformation. You will find articles about health, fitness, medical care, psychology, and professional development on my site. As the husband of a real estate agent, you will also find real estate and housing tips.

Atlanta, GA

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