Individual differences in pain: understanding the mosaic that makes pain personal

Abstract

The experience of pain is characterized by tremendous inter-individual variability. Multiple biological and psychosocial variables contribute to these individual differences in pain, including demographic variables, genetic factors, and psychosocial processes. For example, sex, age and ethnic group differences in the prevalence of chronic pain conditions have been widely reported. Moreover, these demographic factors have been associated with responses to experimentally-induced pain. Similarly, both genetic and psychosocial factors contribute to clinical and experimental pain responses. Importantly, these different biopsychosocial influences interact with each other in complex ways to sculpt the experience of pain. Some genetic associations with pain have been found to vary across sex and ethnic group. Moreover, genetic factors also interact with psychosocial factors, including stress and pain catastrophizing, to influence pain. The individual and combined influences of these biological and psychosocial variables results in a unique mosaic of factors that contributes pain in each individual. Understanding these mosaics is critically important in order to provide optimal pain treatment, and future research to further elucidate the nature of these biopsychosocial interactions is needed in order to provide more informed and personalized pain care.

Figure 1

Pain ratings in response to a heat stimulus (48 deg C) by 321 healthy young adults. Each line represents the pain rating (from 0 [no pain] to 100 [most intense pain imaginable]) by a single person. As can be seen, the mean pain rating was 71.8, but ratings ranged from 4 to 100. These data illustrate dramatic inter-individual differences in responses to a standardized experimental pain stimulus.

Figure 2

Patterns of pain prevalence across the adult lifespan. The top panel shows that prevalence increases monotonically with age for several pain conditions, including joint pain, lower extremity pain, and neuropathic pains. The middle panel shows that for general chronic pain, prevalence seems to increase until middle age, at which time it plateaus. The bottom panel shows a pattern of increasing prevalence until middle age followed by a decrease in prevalence in later life for several conditions, including headache, abdominal pain, back pain, chest pain. References supporting these patterns can be found in [32]. It is important to recognize that these prevalence patterns are based on cross-sectional rather than longitudinal data; therefore, one cannot deduce pain trajectories within people from these data.

Figure 3

Biopsychosocial model of pain. The figure illustrates that the experience of pain is sculpted by the influences of biological, psychological and social factors. Notably, while each of these factors can independently influence pain (as depicted by small bidirectional arrows), the more important and complex influences emerge from interactions among the factors, as depicted by the larger three-way arrows. These interactions among multiple biopsychosocial factors results in a unique mosaic of individual difference factors contributing to pain in each person.