Chronic Pain Explained

Steven D. Feinberg, M.D., M.P.H., M.S. - Board Certified, Physical Medicineand Rehabilitation, Board Certified, Pain Medicine; Adjunct Clinical Professor, Stanford Anesthesiology, Preoperative and Pain Medicine Department, Stanford University - School of Medicine

William M. Zachry, Director, CompSense, Consortium Solutions

Introduction

This paper is intended for workers' compensation claims professionals and attorneys. Its purpose is to explain why people with chronic pain often present in ways that can be confusing, appear inconsistent, or seem out of proportion to objective findings. More importantly, it demonstrates why proper recognition and treatment of chronic pain serves both injured workers' recovery and employers' financial interests—a true alignment of incentives that should guide our approach to these complex cases.

What is Pain?

No two individuals experience pain in quite the same way. The InternationalAssociation for the Study of Pain (IASP) in 2020 redefined pain^[i] as “An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”

When the IASP revised the definition of pain, it intended to convey the nuances and complexity of pain with the hope that it would lead to improved assessment and management for those with pain.

The IASP definition of pain:

• Pain is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors.

• Pain and nociception (tissue damage) are different phenomena. Pain cannot be inferred solely fromactivity in the nervous system.

• Through their life experiences, individuals learn the concept of pain.

• A person’s report of an experience as pain should be respected.

• Although pain usually serves an adaptive role, it may have adverse effects on function and social and psychological well-being.

• Verbal description is only one of several behaviors to express pain; inability to communicate does not negate the possibility that an individual experiences pain.

A multinational, multidisciplinary Task Force developed the revised definition with input from all potential stakeholders, including persons in pain and their caregivers. This definition recognizes the key role of processes in the nervous system and brain (both neurological and psychological) in the experience of pain.

Pain and tissue damage are different phenomena (so the absence of major imaging findings does not mean the person has no pain). Pain cannot be inferred solelyfrom tissue damage or activity in the nervous system, nor can tissue damage or dysfunction be inferred solely from complaints of pain.

Pain Terminology^[ii]

The highly subjective and personalized nature of pain makes it a complex problem todiagnose and treat.

Pain is categorized as:

1. nociceptive (from tissue injury)
2. neuropathic (from nerve injury)
3. nociplastic (pain driven by a highly sensitized nervous system rather than ongoing tissue damage)

Nociceptive pain can coexist with nociceptive and neuropathic mechanisms (mixed pain), which is common in chronic low back pain cases.

Why Can't We Objectively MeasurePain?

There is no current technology that accurately measures pain.

Despite the old idiom “I feel your pain,” no one can feel another person’s pain. While we might commiserate with another, pain is nonetheless very much a personal experience.

Pain is a subjective phenomenon and cannot be measured objectively. Although measures such as heart rate, respiration rate, blood pressure, and sympathetic discharge of the body may indicate the presence of pain, these are not direct measures of a person’s pain and therefore cannot quantify it. In addition, pain scores (0 is no pain and 10 is the worst pain imaginable) cannot be applied universally across people since the meaning of pain varies between individuals; for example, a pain rating of 7/10 may mean a moderate level of tolerable pain to one and a severe level of intolerable pain to another. Therefore, pain scores are best used individually to compare a baseline score against itself in time or in response to the treatment.

The response to pain is affected by the individual's past life experiences, beliefs, and emotional state.

Acute vs. Chronic Pain: KeyDifferences

Acute pain(duration 1-3 months) is a physiological response to noxious stimuli that can become pathological, is normally sudden in onset, time-limited, and often caused by illness, injury, trauma, or medical treatments such as surgery.

Pain is not all bad. Acute pain is an essential part of human life and has survival value. Painful experiences teach us to avoid things that hurt or can physically damage us. Pain may be a sign that something has happened or that something is wrong. Acute pain is usually time-limited and resolves with appropriate treatment. Pain can help us identify diseases, locate the source of bodily damage, avoid injury, and support recovery. In musculoskeletal injuries, acute pain plays an important role in diagnosis and recovery.

Chronic pain (duration of ≥3 months) can be the result of an underlying medical disease or condition, injury, medical treatment, inflammation, or an unknown cause.

Chronic pain usually starts from an injury or disease. However, even after the initial injury has healed or stabilized, the pain persists and relentlessly intensifies.

In chronic pain, physical and psychological factors are typically both present and overlap. Chronic pain is rarely purely physical or only psychological.

Chronic pain disrupts the nervous, immune system, endocrine, inflammatory, and other systems and bodily functions.

How Chronic Pain Affects Lives

Chronic pain systematically dismantles every aspect of a person's life. Physically, it causes unrelenting pain, profound fatigue, sleep disruption, and deconditioning from reduced activity.

Cognitively and emotionally, it impairs concentration and memory, causes depression and anxiety, and creates hopelessness about the future.

Socially, it strains relationships, leads to isolation, dramatically increases divorce and suicide risk, and frequently results in work disability and financial devastation.

The relationship between chronic pain and psychological factors runs in both directions: pre-existing depression, anxiety, or poor coping skills increase vulnerability to developing chronic pain after injury.

Chronic pain can also cause these conditions in people who had none before. This means finding psychological distress doesn't indicate pain is "in their head” - it indicates either a risk factor requiring early intervention or a consequence requiring treatment.

Once chronic pain develops, traditional workers' compensation approaches like prolonged rest, excessive medications (especially opioids), and repeated invasive procedures often worsen outcomes rather than help, as they don't address nervous system dysfunction driving chronic pain and may reinforce disability.

There is thus a challenge in differentiating causes from effects. There is a strong relationship between pain and emotions. Research has confirmed that the severity of depression, anxiety, and anger are some of the most critical factors in determining chronic pain in injured workers with the greatest suffering and dysfunction.^[iii]

Red Flags: Malingering VersusTypical Chronic Pain

Due to the difficulty of diagnosing, differentiating, or substantiating chronic pain, and although not the norm, purposefully lying or exaggerating (malingering^[iv]) can occur and should be ruled out.

Malingering should not be assumed merely because findings are limited. Typical chronic pain behaviors (fear-avoidance, inconsistency, distress) are neurobiologically based responses, not volitional deception. The absence of objective findings does not indicate malingering—this is a fundamental feature of nociplastic pain.

Sometimes, chronic pain is diagnosed as a somatoform symptom disorder^[v] (formerly known as"somatization disorder" or "somatoform disorder"), which isa form of mental illness that causes or exacerbates one or more bodilysymptoms, including pain.

Delayed Recovery Factors

Several factors contribute to delayed recovery from acute injury, increasing the risk of transition to chronic pain in workers' compensation cases. These include biopsychosocial elements such as fear-avoidance behaviors, where individuals limit activity due to pain-related anxiety, leading to deconditioning and amplified pain perception. Catastrophizing—exaggerated negative thinking about pain—and perceived injustice from the claims process further prolong disability, alongside system delays in treatment authorization, poor employer communication, and pre-existing comorbidities like depression or low physical activity. Early screening for these modifiable risks at 6-12 weeks post-injury enables targeted interventions, such as active rehabilitation and psychosocial support, to prevent chronification and support return-to-work.

The Critical Role of Adverse Childhood Experiences

Adverse childhood experiences represent a significant but often overlooked risk factor for chronic pain development and poor treatment outcomes in workers' compensation cases.

Adverse childhood experiences, or ACEs^[vi], are potentially traumatic events that occur in childhood (0-17 years). Examples include:

• Experiencing violence, abuse(sexual, physical, mental), or neglect.

• Witnessing violence in the home or community.

• Having a family member attempt or die by suicide.

Research shows individuals with ≥4 ACEs have significantly worse pain outcomes and lower quality of life, while ≥3 ACEs correlate with higher anxiety and depression.^[vii] Adults exposed to ACEs are approximately twice as likely to develop chronic pain.^[viii] The relationship is mediated through emotion dysregulation, depression, anxiety, and inflammatory pathways. This evidence supports why psychological screening is essential, not optional.

The Uniqueness of Chronic Pain

Pain remains one of the most feared symptoms for injured workers, having significant medical, social, psychological, and financial consequences. While pain can be a symptom of an injury or illness, when pain becomes chronic^[ix] and leads to prolonged suffering, it becomes a disease unto itself and typically can result in disability and dysfunction.

For clinicians, the treatment of chronic pain can be a complex and arduous duty. The difficulty in accurately diagnosing and successfully treating chronic pain can make practitioners feel defeated or discouraged, especially if the presentation is complex and if the worker presents without hope or with a disabled mindset.

The clinician who does not recognize the potential onset or understand the nature of chronic pain may inadvertently contribute to this syndrome by ignoring psychosocial factors and focusing on “fixing” the individual with pills, procedures, and surgery – sometimes with disastrous results.

Acute Biomedical Care vs Biopsychosocial Chronic Pain Rehabilitation

The traditional biomedical model for treating acute injury and pain focuses on repairing tissue damage, surgery, and short-term medications.

A biopsychosocial approach to chronic pain treatment focuses on restoring function, coping skills, and work capacity despite ongoing pain.

The biopsychosocial approach is currently viewed as the most appropriate perspective for understanding, assessing, and treating chronic pain disorders and disability.^{[x][xi] [xii] [xiii] [xiv]}  This whole-person rehabilitation approach encourages the injured worker to take responsibility for their own health and well-being (the “locus of control” is with the injured worker) while learning about their condition. It involves using evidence-based approaches, including minimizing passive therapy and invasive treatments, optimizing medications, and employing psychological pain management and physical restorative treatments.

Multi/interdisciplinary rehabilitation may be cost-effective when targeting patients with severe functional deficits, lack of response to less intensive therapies, or significant psychosocial components.

Communication and Treatment Success

The primary goal is to medically stabilize the injured worker, return to work, and close the case while avoiding massive and unnecessary medical costs.

The best and most effective method to mitigate potential chronic pain issues in workers’ compensation is to promptly determine compensability, communicate the claims process and status with the injured worker, provide immediate quality evidence-based medical care, and identify delayed recovery factors. And, most importantly, working with the doctor and employer to encourage stay-at-work (SAW) and return-to-work (RTW) even when that requires modified duties. In order to attain the best outcome, every effort should be taken to promptly communicate with the healthcare provider, patient, employer, and any other stakeholder who will help the injured worker get expedited treatments in order to return to full functionality and work. Working is the best preventative and best medicine to support and enhance an employee’s perception of being valued and to prevent chronic pain.

Treatment success is achieved by building a bond of trust and communication not only between the injured worker and the clinician but also with the employer, the claims handlers, attorneys, case managers, and others.

The physician–claims interaction is critical towards avoiding authorization delays and care denials.

Working as partners can make the difference between early return to work and a positiveoutcome versus never returning to work, loss of enjoyment of life, high cost, and a resulting chronic pain syndrome.

While an injured worker may have risk factors for delayed recovery (be a potential chronic pain injured worker), this does not rule out the need for medications, procedures, or even surgery. It is important to recognize that these approaches may not have the expected outcome when there are nonphysical factors that are affecting the injured worker.

Some treatment modalities for chronic pain may be inappropriate, such as ever-increasing doses of opioids or experimental or unproven surgeries. The chronic pain-injured worker is at particular risk of inconclusive results, followed by further decompensation from disappointment or frustration with the treatments being provided,  and may be unable to form realistic expectations regarding experimental or investigative treatment options. 

If an injured worker is diagnosed with chronic pain, claims should realize that successful treatment may take time and may also be costly. Treatment may include additional efforts, such as engagement in a functional restoration program.

Injured workers with chronic pain benefit from being well-informed about their diagnosis and the associated treatments. Such education may also entail additional costs in time spent with physicians, therapists, and others. This knowledge may alleviate fears that may interfere with receiving the maximum benefits from carefully and appropriately selected treatments. Education can also prevent unrealistic expectations that lead to disappointment with less-than-expected benefits or even a bad outcome from treatment.

Individuals successful with chronic pain take control of and re-engage in their life activities. They achieve mastery over when and how to access the medical community in ways that are most beneficial for them. The goal is a mitigation of suffering, being independent, and returning to a productive life, including return-to-work, despite a chronic/persistent pain problem.

Workers' Compensation & Chronic Pain

Workers’ compensation benefit delivery systems are complex and difficult for injured workers to navigate and understand. Injured workers can often feel lost in the process. They may feel disbelieved and disrespected, which can fuel a sense of hopelessness and abandonment and may contribute to the development of chronic pain perceptions and poorer outcomes.

Workers’ compensation factors that contribute to creating a chronic pain patient:

• Employers who treat all injuries as fraudulent and injured workers as frauds.

• Employers who do not immediately report all injuries delay prompt compensability determinations and benefits.

• Employers who create barriers that delay return-to-work.

• Employers (front-line supervisors or managers) who do not remain in contact with injured employees (particularly during time off from work).

• Delays in compensability determination by the claims administrator.

• Medical treatment authorization delays result in a lack of access to quality, evidence-based medical care due to a complex and unnecessary authorization process.

• Failure to recognize underlying delayed recovery factors (ACEs).

• Inaccurate or delayed diagnosis by the medical provider.

• Physicians who focus on pathology and not on the whole person.

• Health care providers who do not provide the time for meaningful patient interaction and education.

• Health care providers who do not follow evidence-based medicine treatment protocols.

• Health care providers or the injured worker’s hostility toward the employer/payer.

• Attorneys who do not focus on assisting the injured worker in returning to health and work.

• Lack of communication between stakeholders delays care and leads to chronic pain and unemployability.

Delayed recovery and ever-worsening disability are even more pronounced in individuals with poor coping skills and other behavioral, characterological, personality, and psychological issues. Underlying personality structure and motivation are often determinants of disability. Chronic pain complaints may be linked with significant disability.^[xv]

Action Steps for Claims and LegalTeam

• Screen Early^[xvi]: Chronic pain risk at 6–12 weeks (high pain + fear/kinesiophobia) – Be on the lookout for and recognize:

  • Delayed recovery factors (including ACEs).

  • Escalating and more complex treatment requests without evidence of benefit.

• Minimize delays in compensability determinations and treatment authorizations.

• Make timely referrals for the right treatment:

  • When an injured worker is identified as a risk for chronic pain, make prompt referrals to appropriate medical professionals.

  • Authorize biopsychosocial/functional restoration to cut long-tail costs (MTUS supports).

• Communication and Education: Informed workers RTW faster, settle cleaner (reduces trials).

• Partner: Collaborate with treating doctors on RTW plans to avoid DOR delays.

Summary

Chronic pain is a complex disease of the nervous system and the whole person, not just a symptom of tissue damage, and effective workers’ compensation management requires early recognition, prevention, and coordinated biopsychosocial treatment rather than prolonged passive care or opioids.

Pain is always personal, shaped by biological, psychological, and social factors, and cannot be inferred solely from imaging or other objective tests. No technology can directly and objectively measure pain. Chronic pain dismantles physical, emotional, cognitive, social, and vocational functioning, increasing risks of depression, anxiety, isolation, divorce, suicide, work disability, and financial hardship. Psychological factors both predispose individuals to chronic pain and result from it, so depression or anxiety should be seen as risk factors or consequences needing treatment, not proof that pain is “in the patient’s head.” Typical chronic pain behaviors (fluctuating symptoms, avoidance, apparent inconsistency) are often misread as lack of motivation, obstruction, or malingering, and should be distinguished from intentional lying or exaggeration.

We advocate shifting from an acute biomedical “fix the tissue” model to a biopsychosocial rehabilitation model that addresses biological pathology, psychological factors (fear, catastrophizing, depression), and social factors (work environment, family responses, legal/claims processes). Comprehensive interdisciplinary programs, active rehabilitation, education, and return-to-work focus (rather than endless passive care and escalating opioids) are the most effective strategies, with opioids characterized as rarely appropriate for chronic pain.

Workers’ compensation processes can either prevent or create chronic pain in patients, depending on how they function. System contributors to chronic pain include employers who assume fraud, delays in injury reporting and compensability decisions, treatment authorization delays, lack of modified duty, poor communication, failure to recognize delayed recovery factors such as ACEs, and providers who ignore psychosocial issues or evidence-based guidelines. These factors, combined with poor coping skills or personality vulnerabilities, can drive prolonged disability and escalating costs.

For claims professionals and attorneys, we recommend early screening for chronic pain risk at 6–12 weeks (high pain plus fear/avoidance), prompt recognition of delayed recovery factors, and minimization of delays in compensability and treatment authorization. It urges timely referrals to appropriate medical professionals and biopsychosocial/functional restoration programs, close communication and education of injured workers, and active collaboration with treating physicians and employers on stay-at-work/return-to-work plans. The central message is that early, coordinated, function-focused management of chronic pain both improves outcomes for injured workers and reduces long-tail claims costs for employers and payers.

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REFERENCES

1. ACPA–Stanford Resource Guide to Chronic Pain Management: An Integrated Guide to Comprehensive Pain Therapies.

2. Stretanski MF, Kopitnik NL, Matha A, et al. Chronic Pain. [Updated 2025 Sep 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553030/

3. Wang J, Doan LV. Clinical pain management: Current practice and recent innovations in research. Cell Rep Med. 2024 Oct 15;5(10):101786. doi:10.1016/j.xcrm.2024.101786. Epub 2024 Oct 8. PMID: 39383871; PMCID: PMC11513809. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11513809/

ENDNOTES

^[i] Terminology | International Association for the Study of Pain (iasp-pain.org)

^[ii] Terminology | International Association for the Study of Pain (iasp-pain.org)

^[iii] Gilam G. et al. Classifying chronic pain using multidimensional pain-agnostic symptom assessments and clustering analysis. Science Advances. 8 Sep 2021;7(37). DOI:10.1126/sciadv.abj0320

^[iv] Malingering is falsification or profound exaggeration of illness (physical or mental) to gain external benefits such as avoiding work or responsibility, seeking drugs, avoiding trial, seeking attention, avoiding military services, leave from school, paid leave from a job, among others. It is not a psychiatric illness according to DSM-5.

^[v] Somatic symptom disorder (SSD) is characterized by somatic symptoms that are either very distressing or result in significant disruption of functioning, as well as excessive and disproportionate thoughts, feelings, and behaviors regarding those symptoms (DSM-5).

^[vi] Center for Disease Control (CDC): Adverse Childhood Experiences (ACEs)

^[vii] Craner JR, Lake ES, Barr AC, Kirby KE, O’Neill M. Childhood Adversity Among Adults With Chronic Pain: Prevalence and Association With Pain-related Outcomes. Clin J Pain. 2022 Sep 1;38(9):551-561. doi:10.1097/AJP.0000000000001054. PMID: 35777964.

^[viii] Dalechek DE, Caes L, McIntosh G, Whittaker AC. Anxiety, history of childhood adversity, and experiencing chronic pain in adulthood: A systematic literature review and meta-analysis. Eur J Pain. 2024 Jul;28(6):867-885. doi:10.1002/ejp.2232. Epub 2024 Jan 8. PMID: 38189218.

^[ix] Chronic (or persistent) pain can be described as ongoing or recurrent pain, lasting beyond the usual course of acute illness or injury healing.

^[x] Gatchel RJ. Comorbidity of chronic mental and physical health disorders: The biopsychosocial perspective. American Psychologist. 2004;59:792-805.

^[xi] Gatchel RJ. Clinical Essentials of Pain Management. American Psychological Association, Washington, DC, 2005.

^[xii] Gatchel RJ, Okifuji A. Evidence-based scientific data documenting the treatment- and cost-effectiveness of comprehensive pain programs for chronic nonmalignant pain. Journal of Pain. 2006;7:779-793.

^[xiii] Turk DC, Gatchel RJ (Eds.). Psychological Approaches to Pain Management: A Practitioner’s Handbook, 2nd ed. Guilford, New York, 2002.

^[xiv] Turk DC, Monarch ES. Biopsychosocial perspective on chronic pain. In: Turk DC, Gatchel RJ (Eds.), Psychological Approaches to Pain Management: A Practitioner’s Handbook, 2nd ed. Guilford, New York, 2002.

^[xv] Aronoff GM. Chronic pain and the disability epidemic. Clin J Pain. 1991;7:330-338.

^[xvi] Examples of tools: The STarT Back Tool (9 questions assessing pain and psychosocial factors), Örebro Musculoskeletal Pain Screening Questionnaire (25 items predicting chronicity and work absenteeism), and the Traumatic Injuries Distress Scale (TIDS) for peritraumatic distress.