The Biopsychosocial Model Helps Explain Complex Differences in Pain

When understanding biology alone is not enough. Image credit: iqoncept/123RF Stock Photo.

A consideration of biology alone is not enough to understand chronic pain. Image credit: iqoncept/123RF Stock Photo.

Editor’s Note: The first-ever North American Pain School (NAPS) took place from June 26-30, 2016 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, PhD candidate Pauline Voon describes a talk delivered by Roger Fillingim, a pain researcher at the University of Florida, who described the “biopsychosocial model” of chronic pain and how it is guiding pain research.

At the North American Pain School, Roger Fillingim recalled his experiences as a clinician treating chronic pain nearly twenty-five years ago. One particular patient stood out to him: a gentleman with chronic low back pain, two unsuccessful surgeries, and multilevel disc degeneration. For many pain clinicians and researchers–even today–these details about the patient’s medical history would be the primary focus of their attention.

However, there were many more important factors at play that may have been contributing to the patient’s pain: he was a 45-year-old former iron worker on worker’s compensation, had not completed high school and was functionally illiterate, and had a history of panic disorder, depression, and heart attack. Unfortunately, many people who treat and research pain often overlook such important aspects of the patient’s life history.

“Let’s treat his pain as though it’s a single entity, and ignore everything else about his life—that’s not going to work very well for us,” Fillingim said. “And this is not an uncommon example; it’s relatively common for people with long-term pain.”

The take-home message of Fillingim’s talk was that understanding the experience of patients with chronic pain, and knowing how best to treat them, requires a perspective that goes beyond considering only biological factors.

“What we now think is particularly helpful is the biopsychosocial model, which tells us that the experience of pain and responses to pain are sculpted by complex and dynamic interactions of biological, psychological, and sociocultural factors,” he said.

Advancing beyond the biomedical model
The biopsychosocial model of pain was introduced by George Engel in 1977 in an article in the journal Science. Engel was frustrated that the biomedical field was not appreciating the complexity of factors that contribute to disease. He argued that the biomedical model, which focuses on understanding the biological processes underlying disease, needed to be replaced, for several reasons.

For example, biological processes that go awry in disease do not by themselves explain the clinical symptoms or maladies that people may have. While an x-ray or MRI scan can show where a physical injury occurs in the body, the pictures from these scans do not fully explain differences in the amount of pain or disability that two individuals living with the same condition may show.

“We don’t treat disease—we treat people in a context of their lives who happen to have a disease,” said Fillingim. “And the life conditions in which people find themselves have a tremendous impact on the disease itself.”

Fillingim explained how psychosocial factors can also influence whether people think they are sick. There are some symptoms that are accepted as ‘normal’ in some cultures or circumstances, whereas the same symptoms in other cultures or circumstances might be considered as an indication of illness. Additionally, social interactions between patients and healthcare providers have a profound impact on treatment outcomes, especially when it comes to pain management.

The biopsychosocial model of pain in action
Building on the purely biomedical model of pain, the biopsychosocial model of pain takes into account complex interactions between biological factors (e.g., hormones, genetics, and the body’s natural pain-killing compounds, known as endogenous opioids), psychological factors (e.g., mood, pain coping, and pain catastrophizing), and social factors (e.g., gender roles, ethnic identity, discrimination, and healthcare provider bias) that may contribute to pain. As a result, Fillingim said the biopsychosocial model is better able to answer complex questions related to pain treatment and research, such as who is at higher risk for certain types of pain, why individuals may respond differently to pain, and why it is generally ineffective to provide only a single form of treatment for pain.

For example, consider why some people react to painful stimuli in vastly different ways. Fillingim tested this in an experimental setting by applying a 48-degree Celsius (118 degree Fahrenheit) heat stimulus on a healthy group of 321 study participants. He found that there were remarkable differences in how people rated the severity of their pain, even though they had received the same pain stimulus. Fillingim explained how a variety of factors such as sex, race, age, genetics, blood pressure, expectations, anxiety, and the influence of the experimenter could contribute to these differences in pain sensitivity. “These are the individual differences that we’re faced with. Most people see this as a nuisance; I see it as a career,” he said humorously.

Indeed, work from Fillingim and colleagues has revealed numerous biopsychosocial factors that may contribute to individual differences in pain. For instance, studies have shown an interaction between genetics and sex in pain sensitivity; an interaction between genetics and ethnicity in pain sensitivity; and an interaction between sex, stress, and genetics in pain sensitivity and pain relief.

His work has also revealed an influence of sleep quality and an interaction between stress and genetics in jaw pain; racial/ethnic differences in older adults with knee osteoarthritis; and an influence of genetics and psychological factors in shoulder pain.

“We need to maintain this perspective that pain is complex,” he said. “Pain is not in a niche. It is in a complex person living in a complex world.”

Pauline Voon is a PhD candidate in population and public health at the University of British Columbia, Vancouver, Canada.