Pain management providers in the field tend to be eclectic and flexible in their choice of modalities and attempt different treatments until they find something that suits the patient, a phenomenon known as the “Goldilocks effect” which derives from the children’s story The Story of the Three Bears. Research studies in pain management have concluded that the diverse treatment interventions currently available all appear to be equivocally effective. In the past, the practice of psychotherapy confronted a similar issue-- research studies concluded that all psychotherapies were effective which led to a verdict later termed the “Dodo bird effect” referencing a scene from Alice’s Adventures in Wonderland. This conclusion led to the distinction of two possible mechanisms of psychotherapeutic change, specific versus non-specific effects, also known as “common factors.” The purpose of the current review is to outline the applicability of the common factors model to pain management and provide supportive evidence from existing research.

Keywords:chronic pain, pain management, common factors, dodo bird effect

Chronic pain is a pervasive problem that affects about 20% of adults globally, and continues to grow annually by 10% with newly diagnosed patients.¹ In the past two decades, the field of pain management has witnessed advances in the understanding of the mechanisms of pain and the application and practice of pharmacological, interventional, physical, psychological, rehabilitative, and alternative modalities in the treatment of pain. According to the International Association for the Study of Pain, pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of tissue damage, or both”.² This definition is the culmination of centuries of ideas and work that have explored the concept of pain. Pain can be classified as acute pain (last a moment to weeks or longer, and is typically associated with tissue injury or disease) and chronic, or persistent, pain (pain signals remain active in the nervous system beyond the normal time of healing, and does not have a simple or immediate treatment).

Traditional, “bio-medical” methods used to treat acute pain have proven unacceptable in the treatment of chronic, non-cancer pain. Bio-medical methods tend to utilize technology as its diagnostic strategy, are short-term in time span, assess the cause, and define pain as a symptom which separates the body and mind relationship. Single modalities of treatment, whether they are pharmacological, interventional, physical, psychological, rehabilitative, or an alternative modality, rarely have been found to be sufficient in the treatment of chronic pain.³ Thus, the rules about treating chronic pain have changed in the medical field in the past two decades. Governing agencies have suggested that if pain persists beyond three to six months, or the normal time of healing, then the patient should be approached using the “bio-psycho-social” method. The bio-psycho-social method suggests that the pain provider not only identify bio-medical factors, but also encourages them to focus on the psychological and social elements (including spiritual) of the individual which are believed to be responsible for the persistence of the pain.⁴ Bio-psycho-social methods tend to utilize comprehensive psychosocial diagnostic strategies, are long-term in time span, assess the effects of pain, and define pain as a complex problem which acknowledges the need to treat the whole person, mind, body, and spirit.

Effective pain management has been deemed a human right,^5,6 but some chronic pain patients perceive that to mean they are entitled to opioid analgesics for prolonged pain control.⁷ In response to these expectations, physicians may feel pressured to continue prescribing opioids-thereby reinforcing the patient’s beliefs and reliance on medication.⁸ This has contributed to a dramatic rise in opioid analgesic misuse and a death from prescription drug overdose,⁹ and was identified in 2013 by the Centers for Disease Control and Prevention¹⁰ as a “public health epidemic.” Unfortunately, the medical education system lags behind with regards to teaching future practitioners the difference between treating acute versus chronic, non-cancer pain.^11,12 Providers may consider several factors when choosing a treatment for pain, including pain-related, individual-related, and environment factors. Thus, providers in the field of pain management tend to be eclectic and flexible in their choice of treatment methods and try different treatments until they find something that suits the patient, a phenomenon known as the “Goldilocks effect” which derives from the children’s story The Story of the Three Bears.¹³ As a result, research has shown that the overall treatment effectiveness for chronic pain remains inconsistent and fairly poor.

A general conclusion about the treatment of chronic, non-cancer pain is that the results presented are disheartening. Of all the treatment modalities delineated below, the best evidence for pain reduction averages around 30% in about half of treated patients.³ In other words, one could only expect for a person suffering from chronic, non-cancer pain reporting a “9” on the Numeric Rating Scale (with “0” meaning no pain, “1 to 3” mild pain, “4 to 6” moderate pain, and “7 to 10” severe pain) to see a three point reduction in their severity score half of the time. Clinical trials have indicated the comparable efficacy of numerous diverse treatment interventions, such as acupuncture, behavioral therapy, exercise therapy, and non-steroidal anti-inflammatory medications, for chronic, non-cancer pain.¹⁴ Overall, the current evidence provides little support for choosing one approach over another. The following is a review of the effectiveness of treatments for chronic, non-cancer pain. An appraisal of treatments for specific diagnoses is beyond the scope of this examination.

Pharmacological treatments

Medication management has continued to be the mainstay of chronic pain treatment over the past two decades. The classes of drugs most commonly used for the treatment of chronic, non-cancer pain are opioids, non-steroidal anti-inflammatory drugs (NSAIDs), antidepressants, anticonvulsants, muscle relaxants, and topical agents. The effectiveness of opioids has been evaluated for the treatment of various forms of chronic, non-cancer pain using a meta-analysis. The study strongly concluded that opioids result in small improvements in pain severity and function compared with placebo.¹⁵ The efficacy of NSAIDs has been established for some patients with pain (i.e., arthritis and back), but has not been investigated in others (i.e. neuropathic pain and fibromyalgia).^16,17 Meta-analyses have also suggested that antidepressants result in moderate symptom reduction and are superior to placebo for the treatment of chronic, non-cancer pain.¹⁸ The best evidence supports the efficacy of anticonvulsant drugs for the treatment of chronic, non-cancer pain, specifically gabapentin and pregabalin and carbamazepine.^19–21 Muscle relaxants are typically recommended as adjuvant therapy and seem to have a restricted role in the treatment of chronic, non-cancer pain.^22,23 Topical agents have also been shown to effectively reduce chronic pain in comparison to placebo.²⁴

Interventional treatments

Interventional pain medicine involves the application of various techniques, such as injections, surgery, and implantable devices that can be used for diagnostics or pain relief. Epidural steroid and facet injections are the most commonly used in the U.S.²⁵ However, the evidence for epidural steroid injection use as long-term monotherapy is not clear.^26,27 Facet injections have some evidence for use with facet joint pain, but not clearly effective for other syndromes.^28,29 In terms of surgery, evidence has rated lumber fusion as fair and both discectomy and laminectomy as good,³⁰ with the proviso that significant pain can persist even after spinal surgery.^31,32 Several meta-analyses have evaluated the efficacy of spinal cord stimulation and concluded that there was moderate evidence for improvement in pain.^33–36 A more recent systematic review evaluated the efficacy of epidural and intrathecal drug delivery systems, and determined that there was a moderate reduction in pain but the long-term effectiveness remains unclear.³⁷

Physical medicine and rehabilitation approaches

Evidence suggests that exercise can effectively decrease pain and improve function, but no conclusions can be made about exercise type.³⁸ Physical medicine approaches are commonly included as components of interdisciplinary pain rehabilitation programs. Interdisciplinary pain rehabilitation programs are the embodiment of the bio-psycho-social model of care for patients with chronic pain.³⁹ It has long been recognized that the complexities of chronic pain require the collaborative expertise from multiple disciplines (although the professional staff may vary from one practice setting to another), including pain specialty anesthesiologists, osteopathic physicians, physiatrists, psychologists, pharmacists, and registered nurses. The patient is also considered an integral member of the team, and is responsible for self-management which may include the use of heat/ice, stretching, walking, repositioning, etc. The reduction of pain after treatment at an interdisciplinary pain rehabilitation program has been reported to be significant.^40–42

Psychological approaches

Psychological treatment as a whole results in modest improvements in pain and physical and emotional functioning, but there is insufficient evidence to recommend one therapeutic approach, such as behavioral therapy, cognitive-behavioral therapy, psychodynamic therapy, stress management, emotional disclosure, biofeedback, and hypnosis, over another.^41–46 Interestingly, the modest reductions in pain severity witnessed with psychological interventions were similar to those noted with pharmacological, interventional, physical, and rehabilitative approaches.⁴⁷

Complementary & alternative approaches

Complementary and Alternative Medicine (CAM) is a group of medical and health care systems, practices, and products which can be categorized into four general categories: mind-body medicine (e.g., biofeedback, hypnosis, yoga), natural-biological based (e.g., aromatherapy and herbs), manipulation-body based (e.g., chiropractor, massage, spinal manipulation), and energy medicine (e.g., acupuncture and healing touch). There is promising scientific evidence to support the use of CAM for non-cancer pain conditions, such as low back pain (e.g. massage, spinal manipulation, progressive relaxation, and yoga), arthritis (e.g. acupuncture), and headaches (e.g. acupuncture and spinal manipulation); and limited support for neck pain (e.g. acupuncture and spinal manipulation) (National Center for Complementary & Alternative Medicine, 2014).⁴⁸

The practice of psychotherapy confronted a similar issue, deciding which approach to choose over another, in the past. The field of pain management may be able to glean insight from the psychological research literature in “common factors.” The purpose of the current review is to outline the applicability of the common factors model to pain management and provide supportive evidence from existing research.

References to the concept of “common factors” in psychotherapy began as early as 1936.⁴⁹ At that time, research studies were concluding that all psychotherapies were effective and “all must have prizes,” a verdict later termed the “Dodo bird effect” which references a scene from Alice’s Adventures in Wonderland. ⁵⁰ It wasn’t until 1952 when Eysenck⁵¹ announced his refutation, psychotherapy did not lead to improved patient outcomes, that research into the efficacy of psychotherapy witnessed resurgence. It was then when discussions about common factors began to appear in psychology textbooks and manuscripts. Soon thereafter, several meta-analyses have illustrated the absolute efficacy of psychotherapy.^50,52–54 Two important findings have been noted from those analyses, 1) that improved research methods did not increase the effects found and 2) that effect sizes were comparable across all treatments.

These conclusions led to the distinction of two possible mechanisms of psychotherapeutic change, specific versus non-specific effects. Specific effects were associated with unique interventions to certain therapy approaches, while non-specific effects were linked with contextual factors of the clinical encounter (Figure 1). Evidence from systematic reviews of diverse psychotherapy interventions indicate that factors common across therapies contribute more to treatment outcomes than effects associated with specific technical interventions.^55,56 Specific groupings and examples of these “common factors” were later categorized into five areas, including change processes, therapist qualities, relationship elements, treatment structures, and client characteristics. Meta-analytic studies then summarized psychotherapy outcome research and reduced the factors into four areas, including client factors (explaining 40% of the variance in outcomes), therapeutic relationship factors (30%), expectancy/placebo/hope (15%), and techniques/models (15%).^57,58 This research later inspired a book on common factors theory titled The Great Psychotherapy Debate.⁵⁶ It concluded that non-specific effects were responsible for more than four times the amount of variance in treatment outcomes across various interventions.

Figure 1 Common Factors Model in Pain Management.

A common factor speaks to pain management being an art form in addition to a science. From a psychotherapy perspective, specific interventions, such as techniques/models discussed previously, will not be fully effective without the contribution from the other common factors. The following is a review of the evaluative evidence (including theoretical and literature reviews) indicating that factors common across all therapies, such as patient factors, therapeutic relationship factors, and expectancy/placebo/hope, may also be responsible for general effects in pain management (Tables 1-3). English-language articles and books were identified through the Google Scholar database when searched for approximately the last thirty years. Many of the themes under each common factor put forth had overlapping content and thus were parceled by the dominant theme.

Patient factors

Patient factors are characteristics of the patient and his/her environment. Several different themes were explored when investigating the current research literature on patient factors, such as remission, inner strength, resiliency, goal directedness, purpose, motivation, personal agency, sense of control, fortuitous events, by chance, social support, faith, life experiences, strengths and abilities, and readiness to change. More than twenty retrieved articles were related to this factor (Table 1). Themes such as faith, strengths/abilities, and social support seemed to have more literature related to it than other themes like motivation whose model of pain management was only recently developed. In summarizing the findings from the various studies, it would appear that treatment outcomes were better when the patient:

1. was employed which affects remission
2. had high treatment outcome expectations
3. was resilient and remained positive
4. was engaged in activities that were purposeful
5. was motivated to manage pain
6. had an internal locus of control
7. felt they had control over their pain
8. perceived having social support
9. believed in God or a spiritual power greater than themselves
10. did not experience any recent/daily life stressors
11. had positive beliefs and used coping strategies
12. had an increased readiness for change

Therapeutic relationship factors

Therapeutic relationship factors are perhaps the most researched common factor, besides the specific interventions. The therapeutic relationship, or therapeutic alliance, is a psychotherapy common factor identified by Grencavage & Norcross.⁵⁹ Therapeutic relationship factors are characteristics of the provider and the patient that facilitate change and are present regardless of the type of intervention. Several different themes were explored when investigating the current research literature on therapeutic relationship factors, including empathy, warmth, respect, genuineness, acceptance, encouragement and instruction, communication, and the patient-provider relationship. Approximately 25 retrieved articles were related to this factor (Table 2). Themes such as the patient-provider relationship and encouragement/instruction seemed to have more literature related to it than other themes like warmth. In summarizing the findings from the many examinations, it would appear that:

1. provider empathy plays a crucial role in pain treatment
2. providers who are warm are more effective
3. patients are more satisfied when they perceive they are respected by providers
4. patient suffering may be affected by acknowledgement of genuineness of pain
5. patient need to reframe treatment as acceptance of chronic pain
6. patient encouragement and instruction decreases pain and increases satisfaction
7. the communication process influences self-management of pain
8. patient-provider relationship is significantly associated with outcome

Expectancy factors

Expectancy factors are improvements that result from the patient and provider’s belief that treatment is effective. Several different themes were explored when investigating the current research literature on expectancy factors, such as expectations, placebo, noncompliance, relapse, optimism, hope, and credibility. Themes such as expectations seemed to have the most literature available. Almost twenty retrieved articles were related to this factor (Table 3). In summarizing the results from numerous investigations, it would appear that treatment outcomes were enhanced when:

1. patients’ expect and believe treatment is potentially beneficial
2. providers consider how placebo effects and regression to the mean improve outcomes
3. providers consider the patient’s potential to be noncompliant and relapse
4. patients are optimistic, have hope, and/or accept their pain
5. patients feel providers believe their pain is credible

Other factors

While conducting the current literature review, several common themes that are aligned with the pain medicine environment began to appear and reoccur throughout the search, including healthcare system, sociocultural, ethical/legal, and disease specific factors. In terms of healthcare system factors, it appears that the approach utilized to treat chronic pain in the healthcare system may have an effect on outcomes. For example, Pérula de Torres et al.,⁶⁰ compared usual treatment from family physicians with the patient-centered approach in a primary care setting, and found significantly better results in self-rated pain and physical mobility in the patients who received care using the patient-centered approach. They further suggests that providers combine the patient-centered approach with other common factors aforementioned, including defining the illness and communicating it to the patient; offering support and being friendly, approachable, and empathic; engaging in mutual discussion and partnership; and providing clear information and looking for common ground.

There is also research which indicates that sociocultural factors may play a role in chronic pain outcomes. Sociocultural factors are the larger scale forces within cultures and societies that affect the thoughts, feelings, and behaviors of individuals. Sociocultural factors related to the pain experience may include pain expression, pain language, lay remedies for pain, social roles, tangibles, and perceptions of the medical care system. Sanchez-Ayendez et al.,⁶¹ evaluated how cultural values, standards, and beliefs in New England versus Puerto Rico affect health care professionals’ responses to patients’ pain, patient-provider relationships, and the patients’ responses to illness. They found dissimilarities in cultural views about the mind-body relationship between the two different health care contexts which in turn affected patient’s pain. Bair et al.,⁶² identified several issues with tangibles, such as transportation and finances, as being barriers to self-management among patients who suffer from chronic pain. Matthias et al.,⁶³ also concluded that the needs of pain management provider’s, including instrumental support, cannot be ignored when considering patient pain care.

There are ethical and legal factors which influence the practice of pain management. Effective pain management has been deemed a right to health according to international human rights law. Thus, inadequate pain treatment is considered a violation to protect against cruel, inhuman, and degrading treatment. Chamberlain et al.,⁶⁴ analyzed the narratives of patients who suffer from low back pain, and found they also perceive pain as being a “moral event,” or concerning priorities and attitudes. As a result, providers may alter their practice in response to these expectations. However, it remains difficult to support this position as a point of law or as a matter of ethics.

Research also suggests that there are disease specific factors which influence the practice of pain management. Previous analyses show that high pain expectancy substantially increases pain. However, attention to the body reduced pain, partially suppressing the effects of expectancy. Furthermore, increased body focus had larger pain-reducing effects when pain expectancy was high, suggesting that attempts to focus on external distracters are counter-productive in this situation. Overall, the results show that attention to the body cannot explain pain enhancing expectancy effects, and that focusing on sensory/discriminative aspects of pain might be a useful pain-regulation strategy when severe pain is expected.⁶⁵

Using models developed in other professions to inform inquiry in another field is appropriate and there is some precedence in the literature, specifically in physical medicine and rehabilitation.⁶⁶ The current review explored the applicability of the common factors model to pain management and provided supportive evidence from existing research. Research studies in pain management have concluded that the diverse treatment interventions currently available all appear to be equivocally effective, a verdict one should propose be termed the “Manumea effect.” This term references Samoa’s endangered counterpart to the dodo bird, which is apropos since it is a relative of the famously extinct bird (alike pain management and psychotherapy being relative) and its cryptic, almost invisible, nature (alike the use of common factors model in pain medicine being obscure). Even though a common factors model in pain management is not fully developed, such a model should be considered in order to further advance knowledge and practice in pain medicine. The true causes of improvements in pain after treatment remain unknown in the absence of independently evaluated randomized controlled trials. Additional research is needed to more clearly define the common factors model in pain management, specifically in 1) defining common factor categories which are more aligned with the pain medicine environment (e.g. healthcare system, sociocultural, ethical/legal, and/or disease specific factors); 2) estimating the impact of common factors on outcomes in comparison to the specific pain treatments; and 3) exploring the inter-relationships of the common factors. Only then will we be able to increase the effectiveness and quality of health services during pain medicine consultations.

None.

Author declares there are no conflicts of interest.

None.

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