Classifying Chronic Pain Using the American Pain Society’s Taxonomy

A complex and challenging condition to effectively and optimally manage, chronic pain places significant burden on the individual and the society as a whole.

The subjective nature of chronic pain and the wide individual variation in its tolerance suggest that physiological factors may not be the only ones playing a role in an individual’s pain experience.¹

Experimental and clinical studies have identified key psychological processes that both appear to have a powerful influence on the nature and development of chronic pain, and on an individual’s perception and response to pain.^2,3

In fact, a systematic review identified several psychosocial variables that contribute to the transition from acute to chronic pain.² These factors, considered to have a greater influence than biomedical and social variables, include previous traumatic experience in childhood, challenges and distress in daily life, coping behavior, anxiety, depression and work dissatisfaction.

In addition, catastrophizing, beliefs, and suppressing or ignoring pain as a coping strategy can worsen the pain experience, affect the response to analgesic medications, and increase the risk of chronicity of acute pain.^2,4 The numerous studies indicating a significant role of psychosocial influences on chronic pain suggest that its optimal management should include strategies to improve psychological well-being.

Therefore, a chronic pain management strategy focused on a biopsychosocial model of pain, incorporating psychosocial screening with biomedical-targeted interventions may be a cost-effective way of improving clinical outcomes.⁵ Additional evidence highlighting the influence of psychosocial factors as mediators and moderators of chronic pain is necessary, in order to better design treatments. ⁴

The complexity and individual variability of the chronic pain experience highlights the need for a comprehensive approach to its assessment. A variety of approaches have been used to develop diagnostic criteria for chronic pain, however, current approaches to chronic pain classification, and on which the diagnostic criteria are based, lack an evidence-based taxonomy.

Furthermore, the existing diagnostic approaches typically do not take into consideration, or incorporate the evidence that support the influence of biopsychosocial mechanisms in modulating the pain experience.⁶

An empirically based pain classification system that recognizes individual differences as well as the significant influence of biopsychosocial domains in the pain experience, can serve to inform policy, clarify prognosis, guide treatment decisions, and overall, improve pain management.

The Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities, and Networks (ACTTION) initiative is a public-private partnership, in collaboration with the United States Food and Drug Administration (FDA), designed to expedite the discovery and development of safer and more efficacious analgesic medications.^4,6

In partnership with the American Pain Society, an evidence-based chronic pain classification system – the ACTTION-American Pain Society Pain Taxonomy (AAPT) was developed to address the need for evidence-based diagnostic criteria for the major chronic pain conditions.^1,4 

AAPT recognizes and incorporates psychosocial concepts and processes in its assessment of chronic pain.⁶ A significant advance from the core diagnostic criteria currently used for numerous pain conditions (dimension 1), the AAPT also provides dimensions on which to categorize common features and comorbidities of chronic pain (dimensions 2 and 3), as well as detailing the consequences (dimension 4) and the contributory mechanisms (dimension 5).⁴

These dimensions, individually and collectively, are variables that can provide assessment of the risk for developing a chronic pain condition from acute pain, the severity of pain-related consequences such as disability, and the success or failure of various pain treatments.

The AAPT classification system is a positive contribution to improving the management of chronic pain, as it enables the assessment of the multidimensional contributors to the pain experience by incorporating the psychosocial influences.

Assessing the psychosocial components of chronic pain does not necessarily translate to improved treatment and outcomes. It is essential that a treatment strategy is designed to improve not only physical function, but also affect improvement in the psychosocial domains, such as catastrophizing, self-efficacy, depression, and improved coping skills.

It is necessary that clinicians identify specific psychosocial factors that may be perceived by their patients as obstacles to their response to treatment or recovery from their condition. This approach must be individualized so that a highly distressed and challenged individual with chronic pain may require more specific psychological expertise, compared to an individual with less severe psychosocial problems.

Such a strategy offers a patient-centered approach to pain management in which psychological principles are blended with a biomedical approach for individualized patient care.

Summary and Clinical Applicability

Improved understanding of the social influences on the perception of pain and response to treatment offer new approaches to classification and treatment of chronic pain.

The AAPT is an evidence-based multidimensional chronic pain classification system that incorporates psychosocial concepts and processes in the assessment of chronic pain. The improved classification of chronic pain offers opportunity to broaden and enhance therapeutic interventions that may include more effective blending of psychological intervention with a biomedical approach to chronic pain management.