전체메뉴
Search
Article Search

JoP

Review Article

Split Viewer

Related articles in JAMS

More Related Articles

Article

Review Article

2008; 1(1): 1-12

Published online September 1, 2008 https://doi.org/10.1016/S2005-2901(09)60001-7

Copyright © Medical Association of Pharmacopuncture Institute.

A Review of Psychosocial Predictors of Treatment Outcomes: What Factors Might Determine the Clinical Success of Acupuncture for Pain?

Felicity L. Bishop*, George T. Lewith

Complementary Medicine Research Unit, University of Southampton, UK

Correspondence to:Felicity L. Bishop

Received: February 26, 2008; Accepted: March 5, 2008

http://creativecommons.org/licenses/by-nc-nd/4.0/

Abstract

This narrative review examines the psychosocial factors that might predict clinical outcomes in acupuncture for pain. Given existing evidence concerning the clinical effectiveness and safety of acupuncture in painful conditions, it is important to consider how clinicians might further improve their effectiveness. The relevant theoretical frameworks focus primarily on the patient, suggesting that their background characteristics and their beliefs about pain and acupuncture should be considered as potential predictors of outcome. The self-regulation model within health psychology helps us understand how people manage their health and integrate interventions like acupuncture into the management of their illness. This model also implies that the therapeutic relationship, in particular patients' perceptions of that relationship, is likely to be related to outcome. The empirical literature in this area is sparse. However, the findings to date do suggest that a number of psychosocial factors, in particular patients' beliefs about acupuncture, are significant predictors of treatment outcomes from acupuncture for pain. Factors related to the therapeutic relationship are also likely to be important in facilitating good clinical outcomes. We discuss the limitations of the existing studies and make recommendations for future research in this area. If we can better understand the psychosocial factors involved in acupuncture, then we should be able to enhance acupuncture treatments and improve outcomes for patients. These observations will, therefore, have potential to allow us to develop techniques that may improve clinical outcomes in the treatment of pain.

Keywords: acupuncture, attitude to health, outcome and process assessment, placebo effect, review

1. Introduction: Acupuncture for Pain

Chronic pain is common and costly with existing treatments having limited success: 40% of chronic pain patients in a recent European survey (2003) reported inadequate pain management with 13% of those surveyed having used acupuncture for their pain [1]. In the United States, 4.1% of the total population surveyed in 2002 had visited an acupuncturist at some time [2] as had 1.6% of the UK general public (1998) [3]. Many British general practitioners (GPs) also hold positive beliefs about this intervention. The British Medical Acupuncture Society estimates that approximately 3500 doctors use acupuncture themselves while two thirds of GPs believe acupuncture should be available on the National Health Service [4].

There is growing evidence from randomized controlled trials (RCTs) and meta-analyses that acupuncture has clinically significant effects (efficacy over placebo controls) in chronic back pain [5, 6, 7, 8] and other painful conditions including neck pain [9, 10], osteoarthritis of the knee [11], migraine [12] and tension headache [13, 14]. There is good evidence that acupuncture is both extremely safe [15, 16] as well as being a cost-effective intervention for persistent [17] and chronic low back pain [18], chronic neck pain [19] and headache [20]. There is also growing indirect evidence that acupuncture has large nonspecific clinical effects, in addition to any specific efficacy. The variation in the proportion of patients reporting improvements across different individual trials suggests the presence of mediating factors that contribute to positive clinical outcomes. Furthermore, in RCTs both placebo acupuncture and real acupuncture can have similarly large effects compared with waiting list controls or “treatment as usual” [7]. The difference in effectiveness of acupuncture and no acupuncture is far greater than the difference between acupuncture and so-called “placebo acupuncture”. This is similar to the situation for anti-depressants and psychotherapy, both of which are considered effective treatments and both of which have repeatedly demonstrated large nonspecific effects and smaller specific effects [21, 22].

The broader chronic pain literature has a growing focus on treatment process and predictors of outcome [23]. Psychosocial factors have been shown to be important predictors of outcomes such as disability, even when controlling for demographic, clinical and physiological factors [24, 25]. This focus is designed to improve understanding of how individual treatments produce successful outcomes and to suggest whether specific treatments should be targeted to particular patient groups. In the case of acupuncture, the relative contribution of nonspecific effects to overall treatment effectiveness is consistent with the suggestion that psychosocial factors such as patient beliefs about illness and treatment and the therapeutic relationship make a very large contribution to its clinical effectiveness [26]. This makes it both important and feasible to study the psychosocial factors that predict outcomes from acupuncture in the same way as one would for all interventions for chronic pain. The aim of this review is to collate and critique the theoretical and empirical literature concerning the psychosocial factors that might predict outcomes from acupuncture for pain while recognizing that it is probably an effective and cost effective clinical intervention. If we can identify psychosocial factors that predict outcomes in acupuncture then we can use this knowledge clinically to improve the effectiveness of acupuncture for patients with pain.

2. Identifying Psychosocial Factors that might be Associated with Acupuncture Outcomes in Pain

It is one thing to accept that factors other than needle placement might be relevant to acupuncture outcomes, it is quite another to be able to identify them. In this section we consider the insights available from theoretical frameworks and qualitative research concerning which psychosocial factors might be associated with outcomes and why.

2.1. Relevant theoretical frameworks

Theoretical frameworks from placebo research, chronic pain and health psychology identify psychosocial factors that might be associated with treatment outcomes in acupuncture for pain. These frameworks suggest patients' beliefs about and experiences of both chronic pain and acupuncture are probably important determinants of treatment outcomes.

2.1.1. Placebo theories

According to placebo theorists two psychological mechanisms, conditioning and expectancies, are thought to underlie placebo effects [27]. Put very simply, a patient is thought to respond to an inert placebo intervention (often a pill) through: (1) largely unconscious learning mechanisms (i.e. conditioning) through which the placebo intervention (the stimulus) generates pain relief through its (unconscious, learnt) association with previous pain-reducing treatments; and/or (2) largely conscious mechanisms (i.e. expectancy) through which a patient's conscious anticipation that pain reduction (a non-volitional response) will follow a (placebo) intervention has a direct causal effect on the actual non-volitional response of pain reduction [28]. Empirical evidence suggests that conscious expectations mediate the role of conditioning in the context of pain and other conscious physiological processes [29, 30, 31], suggesting patients' expectations of acupuncture in particular might be directly associated with clinical outcome. Indeed there is good evidence that patients' expectations of outcomes are associated with actual outcomes: in one systematic review, 15 of 16 high quality original studies found a significant effect of expectations on outcomes [32]. Placebo theories and studies thus suggest that expectations of acupuncture and, indirectly, past experience of acupuncture might be associated with acupuncture outcomes in pain. Clinically it might be particularly important for patients to have a successful first experience of acupuncture and also to expect to experience pain relief from acupuncture.

2.1.2. A cognitive behavioral model of pain

The fear-avoidance behavioral-cognitive model of chronic pain [33, 34] suggests that patients' beliefs about and responses to pain are key determinants of pain chronicity and can thus strongly influence treatment outcome. According to this theory, patients are more likely to develop chronic pain if they interpret their pain as threatening. This catastrophizing then triggers pain-related fear which is linked to avoidance behaviors and hyper-vigilance to physical sensations. Patients then become more disabled and decrease their activities still further, developing negative affectivity (i.e. depression). Finally patients interpret their pain as more threatening, and the cycle continues. This framework thus focuses on patients' perceptions of pain. The back pain literature supports the importance of patients' pain beliefs for outcomes of multidisciplinary and conventional primary care interventions for back pain. Patients who do not perceive their back pain as threatening (i.e. those who have low scores on measures of catastrophizing) or who consider their back pain as less threatening as it improves over the course of treatment have better treatment outcomes [24, 35, 36, 37, 38]. Patients who report less pain-related fear, or who experience decreasing pain-related fear during a course of treatment, experience better treatment outcomes [37, 39, 40, 41, 42, 43, 44, 45]. Patients who have increased confidence in their ability to manage or cope with pain (higher pain self-efficacy) have improved outcomes [43, 46]; cross-sectional studies also find associations between functional self-efficacy and physical function [47, 48]. Empirical evidence supports the theoretical proposition that specific dimensions of pain beliefs are associated with treatment outcomes in chronic pain and knowing this may help practitioners become better therapists. Three specific factors: catastrophizing, fear and anxiety pain responses, and pain self-efficacy, should be considered as potential predictors of acupuncture outcomes.

2.1.3. A framework from health psychology

Health psychology theory suggests that patients' beliefs about treatment and illness, while important, are not the only potential psychosocial predictors of treatment outcome. An extended version of Leventhal's common sense model of self-regulation [49, 50] also incorporates patients' initial experiences of treatment as potential influences on outcomes. According to this model, people construct representations of their illness and use these to select a potentially effective treatment for their condition. Having initiated a treatment, people then continue to use (adhere to) that treatment while evaluating their experiences of both the treatment itself and the practitioner. Both adherence and patients' appraisals of treatment can influence health status. This model also situates the individual within their broader context, specifying that background variables (such as pain duration, gender, age, work status, psychological health etc.) are related to peoples' beliefs about illness and treatment. This model holds true across a range of settings [51] for example empirical evidence in back pain shows that psychological ill-health is associated with poor outcomes [39, 42, 43, 52, 53, 54]. In addition there is evidence from conventional medicine that patients who have positive evaluations of their practitioner also have better treatment outcomes [55]. According to this model, we should consider two further groups of factors as potential predictors of acupuncture outcomes in pain: background factors (e.g., personal psychological characteristics) and patients' early experiences of the intervention itself, including their therapeutic relationship. For clinicians this suggests a focus on the interpersonal aspects of the consultation, in addition to the acupuncture intervention, might itself help improve clinical outcomes.

2.2. Qualitative research on acupuncture

Qualitative research mostly aims to explore phenomena using a bottom-up approach, grounding emergent themes and theories in participants' everyday experiences. As such, qualitative studies can provide insight into the psychosocial aspects of treatment that acupuncture patients and practitioners value, and hence suggest factors that might be associated with outcomes. Di Blasi suggests that qualitative methods have an important contribution to make in identifying factors that contribute to treatment effects in particular contexts [56]. Indeed this literature does highlight potential predictors of outcome that are not emphasized in the theoretical frameworks reviewed above.

2.2.1. The therapeutic relationship

A number of qualitative studies suggest that both patients and practitioners value the therapeutic relationship in acupuncture [57, 58, 59, 60, 61, 62]. The valued features include its collaborative nature (in comparison to more paternalistic relationships found in conventional medicine), and patients' sense of feeling cared for and their perceptions of practitioners as empathic. These features could be associated directly with positive outcomes, and there is quantitative evidence to support this [55]. It is also possible that patients who value collaborative therapeutic relationships are more likely to benefit from acupuncture than patients who value more paternalistic relationships. Patients and practitioners also value a holistic focus within the therapeutic relationship, which involves a broad approach to health and wellbeing rather than a focus on a single problem [57, 58, 60, 61]. Again, a holistic therapeutic style might, in itself, promote positive outcomes and/or patients who prefer a holistic style might respond better to acupuncture than others. There might be potential for clinicians to enhance outcomes through focusing on patient preferences and their own orientation and beliefs in relation to the therapeutic relationship.

2.2.2. Patient factors

Specific patient-related factors that might be associated with acupuncture outcomes relate to treatment seeking, expectations, perceptions of needling, and personality. Acupuncture patients often seek out acupuncture themselves (particularly in private practice in the United Kingdom), but they can also be offered it by a treating clinician such as a physiotherapist. Whether acupuncture is patient-initiated or clinician-initiated might conceivably impact outcome through an influence on patients' expectations [59]. Whether or not acupuncture treatment is self-initiated, patients come to it with a range of expectations about different aspects of treatment [62, 63, 64]. In one study, patients' expectations (in acupuncture, homeopathy and osteopathy) included complete cure and improved ability to cope with symptoms. They also expected symptomatic relief and improved quality of life as well as interventions with fewer risks than conventional treatments [64]. Patients' expectations regarding a range of outcomes (not just pain) need to be considered as potential outcome predictors. Some patients also hold specific expectations concerning acupuncture needles [62, 63] suggesting that apprehension or anxiety about needles might influence outcomes. Similarly some patients perceive their experiences of needling sensation as important features of acupuncture [59, 63]. The possibility that needling sensation (deqi) might be important for acupuncture outcome is consistent with acupuncture theory [65]. Some qualitative studies, particularly those carried out with a longitudinal perspective, demonstrate the extent of changes that can occur over treatment including changes in patients' beliefs, goals and health behaviors [60, 61, 62]. Patients who are ready to make changes, or who are open to new experiences, might be more likely to benefit from acupuncture. Fostering such positive patient attitudes (if realistic and ethical) might be one way in which clinicians could enhance treatments.

2.2.3. Practitioner factors

Two studies suggest that practitioners' training, skills and attitudes form an important part of the context of acupuncture. These factors might also therefore be associated with treatment outcomes [61, 66]. There are differences between acupuncturists from different theoretical perspectives (TCM/5-elements compared with western acupuncture) in terms of their therapeutic intentions and approaches to treatment [66]. Paterson and Britten describe how acupuncturists' diagnostic and needling skills form an important part of their process model of acupuncture treatment [61]. Patients' perceptions of an acupuncturist's skills might also be indirectly associated with treatment outcome. For example a patient who has low confidence in their acupuncturist's technical skills might therefore also have lower expectations of the efficacy of their treatment, which could then contribute to poorer outcomes.

3. Empirical Evidence of Associations between Psychosocial Factors and Clinical Outcomes

The psychosocial factors that should be considered as potential determinants of acupuncture outcomes in pain are specified in the figure. We have shown how theoretical frameworks and qualitative studies suggest that incorporating an awareness of these factors into clinical practice might enhance patient outcomes. While we have highlighted the potential relevance of this work to clinical practice, it would be unwise and unscientific to recommend changes to practice at this stage; our ideas are purely theoretical at the moment and require evaluation in a relevant clinical environment. In this section we examine the relevant empirical evidence that might contribute to the future development of recommendations concerning practice. We have identified previous studies that have sought to determine whether psychosocial factors predict outcome in acupuncture for pain-related conditions. The literature is relatively sparse, consisting of a loose collection of individual papers which tend to raise more questions than they answer. While we acknowledge that additional studies have been conducted in other populations [67, 68, 69, 70, 71, 72, 73, 74], this review is limited to studies carried out in painful conditions. Using modern meta-analytic techniques is precluded by the enormous heterogeneity within this literature, not only in relation to quality but also in terms of basic study design, potential predictors assessed and outcomes measured. Instead we offer a narrative summary of the published empirical studies before making recommendations for future work to overcome existing limitations.

Figure 1. Psychosocial factors that should be considered as potential predictors of outcome in acupuncture for pain (according to relevant theory and qualitative findings).

3.1. Patient factors

3.1.1. Beliefs about acupuncture

Strong evidence for the role of expectations comes from an interesting analysis by Kalauokalani and colleagues [75]. As part of an RCT for back pain, patients' expectations of massage and acupuncture were assessed before randomization to one of those treatments. Not only were expectations of benefit associated with positive outcomes, but also those patients who expected acupuncture to be superior to massage and received acupuncture had better outcomes than those who received massage, and vice versa. These results held when controlling for a number of covariates, such as baseline health status and socio-demographic factors, although other psychosocial variables (e.g., empathy) were not assessed. Patients with higher expectations had relative odds of improvement that were five times greater than those with lower expectations. Kalauakalani et al also found that patients' general expectations of improvement were not associated with outcomes; patients needed to have expectations that a specific intervention might help them.

Prospective studies have also reported these associations between positive expectations and outcomes. Linde et al [76] pooled data from four very large German acupuncture studies involving RCTs of acupuncture for migraine, tension-type headache, chronic low back pain and knee osteoarthritis. There was a significant relationship between positive expectations (measured at baseline and after 3 sessions) and outcomes (at treatment completion and 6 month follow-up), even when controlling for medical and socio-demographic covariates in a multivariate analysis. In a smaller prospective observational study Harborow and Ogden [77] found that positive expectations at baseline predicted positive changes in overall well-being in a sample of patients with various conditions. Meng et al [78] investigated the impact of expectations on outcome in an RCT of acupuncture for chronic low back pain. Patients who had previous positive experiences of acupuncture had better outcomes than those who reported previous neutral or negative acupuncture experiences, as did patients who reported “positive impressions” of acupuncture.

Weaker evidence for associations between expectations and outcome is provided by studies that measure expectation retrospectively or use measures of treatment credibility as a proxy for expectation. Vas et al [10] found that patients' confidence in using acupuncture treatment in the future or recommending it to others (at the end of treatment) was highly correlated with pain outcomes in an RCT of acupuncture for neck pain. Bausell et al [79] analyzed data from two RCTs of acupuncture analgesia for pain after dental surgery. Although there was no difference between placebo and acupuncture groups, participants' beliefs had a significant effect on outcomes: participants who believed they had real treatment reported significantly less pain than those who believed they had received the placebo treatment.

A number of further studies report mixed findings. Birch and Jamison [80] carried out a small RCT of Japanese acupuncture for myofascial neck pain. Before treatment they assessed patients' past experiences and expectations of acupuncture, and towards the end of treatment they assessed patients' confidence in the acupuncturist and ratings of the credibility of treatment. The only psychosocial factors associated statistically with improvement in pain at the end of treatment were having had previous acupuncture and being confident that acupuncture could alleviate pain in the future (pre-treatment expectations did not predict outcomes). In their RCT of acupuncture for persistent low back pain, Thomas et al [6] examined associations between bodily pain at 24 months and baseline responses to two items: belief that acupuncture could help back pain and expectations of having some improvement in back pain in 6 months time. Patients who expected their back pain to improve had better outcomes than those who did not expect improvement, but patients who were unsure whether their back problem might be helped by acupuncture had better outcomes than those who thought that acupuncture would probably help their back.

Negative findings have also been reported. Lao et al studied the impact of psychological factors on outcomes in a small RCT of acupuncture for pain control after dental surgery [81]. Acupuncture was superior to placebo in controlling dental pain and there were no between-group differences on patients' pre-treatment or post-treatment acupuncture-related beliefs. This pattern of results was interpreted as evidence that psychological factors are not associated with outcome, but no direct test of that hypothesis was reported and so this must be interpreted cautiously. Baischer found no association between expectations and outcome in a small scale observational study of acupuncture for migraine [82]. MacPherson and colleagues similarly found no significant association between expectations and outcomes in a retrospective UK-based observational study [83]. One prospective observational study found that people who had lower, not higher, expectations received significantly more benefit from acupuncture [84].

Published work on treatment beliefs has focused on patients' expectations. However one study by Lu and colleagues [85] suggests that needle phobia, as well as more general expectations of acupuncture, is associated with outcomes. They compared acupuncture and hypnosis in patients with head and neck pain and noted a tendency for patients who had positive attitudes towards acupuncture to experience better outcomes and for patients with acute pain who were needle phobic to experience worse outcomes than those who were not needle phobic.

3.1.2. Beliefs about pain

We identified four studies of pain-related beliefs and acupuncture outcomes. Kreitler et al investigated cognitive orientation in chronic pain patients undergoing acupuncture and found that patients' beliefs about goals, norms, oneself and their general beliefs were strong predictors of improvement after treatment (accounting for 85% of the variance) [86]. The patients who received the most benefit were those whose beliefs were more strongly oriented towards pain relief across the four domains. None of the beliefs were actually explicitly related to either pain or acupuncture, highlighting the importance of the patients' broader psychosocial context. So [84] looked at more general illness beliefs and found that patients who held beliefs that ‘powerful others’ control their health were more likely to benefit from acupuncture. Other beliefs (hopefulness and belief in mind-body dualism) were not significantly associated with outcomes. Toomey et al found no difference between responders and non-responders on a measure of locus of control [87]. Creamer et al also reported no association between self-efficacy and clinical outcomes in a small retrospective study of acupuncture for knee osteoarthritis [88].

3.1.3. Personal characteristics

One early clinical observational study investigated potential psychological mediators of response to acupuncture in chronic pain patients [87]. Toomey et al found that responders (n = 17) were less likely than non-responders (n = 21) to be depressed or exhibit a personality cluster characterized by passivity, overly conventional and stereotyped thought and behavior, and lack of spontaneity. Responders also had lower levels of stress than non-responders, but there were no differences on a number of other dimensions, including locus of control.

Tavola et al examined personality in an RCT of acupuncture for headache [89]. Outcome was not associated with any single dimension on an established personality measure (the MMPI), but the pattern of scores “Conversion V” was associated with poor acupuncture outcomes. (The Conversion V pattern of scores entails high scores of hysteria and hypochondriasis and low scores of depression.) In Baischer's small scale observational study of acupuncture for migraine better outcomes were associated with higher scores on the personality traits extroversion, composure, and sociability, and lower scores on inhibition [82].

Depression has predicted outcomes in two RCTs. Karst and colleagues carried out an RCT of acupuncture for tension headache [90]. Higher depression scores predicted poorer outcomes (higher religiousness scores predicted better outcomes). Furthermore, depression and baseline headache frequency were stronger predictors of outcome than whether a participant received verum or placebo acupuncture. Depression also predicted outcomes in a large multicentre observational study of acupuncture for chronic low back pain [91]. People without depression showed significantly higher improvement in physical health than those with depression; depression did not however relate to changes in pain intensity.

Additional studies have found no significant associations between acupuncture outcomes and personal characteristics. Creamer et al found no evidence for a relationship between clinical outcomes and depression or helplessness, and only non-significant trends for anxiety and fatigue to be negatively associated with pain outcomes [88]. In an early study of acupuncture for dental analgesia, a number of personal characteristics (personality, suggestibility, anxiety and unspecified “attitudes”) did not predict analgesia [92]. Kreitler also found no evidence of an association between personality and acupuncture outcomes [86]. In an RCT of acupuncture and physiotherapy for headache/migraine there were no significant associations between outcomes and seven psychosocial variables (anxiety, depression, psychiatric morbidity, somatization, illness behavior, social problems and quality of marital relationships) [93].

3.2. Therapeutic relationship factors

Compared with the number of studies that have focused on patient factors there have been few published studies on the therapeutic relationship in relation to acupuncture outcomes. Berk et al investigated the role of treatment context and operationalized that concept in such a way as to incorporate both patients' expectations and the therapeutic relationship [94]. Within an RCT of acupuncture for shoulder pain they compared the effect of real acupuncture and placebo acupuncture, each carried out in positive and negative contexts. Patients in the positive context were read positive statements about the effectiveness of acupuncture and were actively engaged in the therapeutic process by the acupuncturist while those in the negative context were read statements that emphasized the doubts and inconsistencies surrounding acupuncture and were discouraged from any communication during treatment. Patients in the positive condition reported more improvements in pain and there were no associations between pain outcomes and scores on validated measures of suggestion and hypnotic susceptibility. These results strongly suggest that the context of the therapeutic relationship is related to acupuncture outcomes, and also highlight the need for further work to elucidate the complex relationships among multiple possible factors.

In a retrospective UK-based observational study, improvements in wellbeing and changes in onés main complaint were associated with a stronger sense of enablement in a sample of patients with various complaints [83]. Patients who perceived their practitioner as more empathetic reported higher enablement scores; enablement scores were not however associated with patients' expectations of treatment and neither empathy nor patient expectations were associated with other outcomes. In a later prospective observational study, Price and colleagues investigated the relationships between empathy, enablement and outcomes in patients receiving acupuncture for various complaints [95]. Empathy was associated with both enablement and health outcomes, and the association between increased perceptions of practitioner empathy and better health outcomes remained significant after statistically controlling for demographic factors and baseline health measures. Indeed perceptions of empathy explained a significant proportion of the variance in outcomes (16%) suggesting that it might have a clinically important effect on outcome.

3.3. Practitioner factors

We could identify few published studies on whether factors related to the practitioner are associated with acupuncture outcomes. Harborow and Ogden [77], as well as measuring patients' expectations of outcome, also measured referring GPs' beliefs about prognosis and the acupuncturist's expectations of success. In addition to patients' expectations predicting outcome, acupuncturists' (but not GPs') positive expectations also predicted positive changes in overall well-being in their patients. Birch and Jamison [80] focused on patients' treatment beliefs (see above), but also measured patients' confidence in their acupuncturist, which was not associated with outcome. A large German observational study of acupuncture for chronic pain found a negligible difference in outcome between practitioners with different amounts of training (140 hours vs. 350 hours training) [96].

4. Current Limitations and Directions for Future Research

4.1. Study design

The majority of studies have been conducted in RCT settings [6, 10, 74, 75, 76, 79, 80, 81, 88, 89, 90, 91, 93]; some observational studies have been carried out in the context of usual clinical practice, with either cross-sectional/retrospective designs [83] or prospective designs [77, 84, 86, 91, 95]. The relative strengths of RCT and observational study designs are summarized in the Table. While RCTs clearly offer a number of advantages, their low external validity constitutes a serious limitation for the study of psychosocial predictors of outcome, to the extent that we would recommend more use of observational designs in future as this will be the only way to understand these potentially important predictors of outcome. Researchers are beginning to explore the contextual differences between RCTs and normal clinical contexts [97, 98]. The evidence suggests that trial settings can have very different implications and meanings for patients and practitioners (compared with usual clinical practice) which will likely translate into differences in expectations and the therapeutic relationship if not other psychosocial factors too. An investigation of certain psychosocial factors within a trial setting might thus have very limited validity when the findings are transferred to everyday clinical practice: observational designs should therefore be considered as offering a vital, ecologically valid, perspective on psychosocial predictors of outcome in acupuncture. However observational studies must be of high quality: adherence to recent gold standards for epidemiological studies could enhance the design and reporting of observational studies of predictors of acupuncture outcomes [99]. There is a lack of potentially useful mixed methods designs that incorporate qualitative approaches. Individual patients' and practitioners' perspectives could be studied using mixed methods to enable explication of the psychosocial processes of change that occur during acupuncture treatment.

Table. A comparison of the strengths of using randomized controlled trials (RCTs) and observational designs to investigate predictors of acupuncture outcomes.

Strengths of RCT designsStrengths of observational designs
More control over the treatment and to an extent the practitioner (increasing the homogeneity of both)Greater external, or ecological, validity: patient and practitioner beliefs are more similar to those encountered in everyday practice, therapeutic relationship factors are more similar to those encountered in everyday practice, patients are more similar to those encountered in everyday practice (e.g., not just attending and being treated for one condition)
More “captive audience” (participants who are already involved in the research and who can complete additional measures of psychosocial factors relatively easily, although this might be considered overly burdensome for them)
Established procedures for outcomes assessment (less burdensome for researchers)
Established inclusion and exclusion criteria for patients (increasing the homogeneity of participants)


4.2. Statistical power and controlling for confounders

Many studies reviewed above rely on small samples of participants (e.g., n < 50 [77, 80, 81, 82, 85, 86, 87, 88, 89, 94, 95]) which can lead to under-powered analyses. While small scale studies are helpful for providing initial tests and generating hypotheses, they have limited potential for furthering our understanding in this area. Importantly, small samples preclude the much-needed inclusion of more than one psychosocial factor within each study and the use of sophisticated multivariate statistics to control for potential confounders.

Results from back pain literature illustrate the importance of carrying out multivariate analyses of psychosocial predictors of outcome. For example, age and pre-treatment pain intensity [41, 45, 53, 100, 101, 102] as well as duration of pain episode [41, 101, 102, 103, 104] and gender [35, 40, 42, 43, 104] have all been shown to influence outcome. Employment and compensation status have also been associated with outcomes [35, 36, 40, 101, 105]. It would seem prudent to take into account both demographic and clinical factors in future analyses of psychosocial predictors of acupuncture outcomes in pain. Larger samples are required in order to conduct the necessary multivariate analyses, and could be achieved either through single large-scale studies [91] or through pooling data from multiple smaller studies [76].

4.3. Validity of measurements

Measures of psychosocial constructs need to be pilot-tested and have strong psychometric properties in order to be considered valid. A number of studies have used unvalidated measures of important variables such as expectations [6, 76, 77, 79] and this clearly raises questions about the validity of their findings. As White has suggested, the poor availability of validated measures of expectancy might explain negative findings [106]. The variation in quality and nature of measures used also makes collating and interpreting the differences across individual studies rather problematic. We recommend the use of standardized core outcome measures [107] to improve comparisons across studies, with the proviso that supplementary acupuncture-specific measures are considered. The further development and consistent use of valid measures of relevant psychosocial factors is also important; a number of existing measures could be improved with further psychometric development [108, 109, 110].

4.4. Theoretical considerations

Many of the studies reviewed above demonstrate little explicit a priori theoretical justification for the factors examined as potential predictors of outcome, and most have not been carried out within existing theoretical frameworks. Future studies would greatly benefit from being grounded within theoretical frameworks and explicitly testing specific hypotheses. It would be impossible to measure all psychosocial factors that could be related to outcome, and taking a theory driven approach can help to identify factors most likely to affect outcome and to develop well-grounded, specific and testable hypotheses. Furthermore, the use of theory-driven and hypothesis-testing approaches could enhance the comparability of individual studies and result in a more cohesive body of knowledge in this area.

Identifying psychosocial predictors of outcome in acupuncture has wider implications for understanding which aspects of acupuncture might be considered characteristic and which might be considered incidental. According to Paterson and Dieppe [111] it is vital to think about acupuncture and other complex interventions in these terms in order to develop appropriate tests of efficacy and effectiveness. Making direct comparisons of psychosocial predictors of outcome across different treatments (e.g., acupuncture and conventional physiotherapy for back pain) has the potential to inform this debate. Such studies have not yet been conducted.

5. Conclusion

The existing literature concerning psychosocial predictors of outcome in acupuncture for pain is both limited and diffuse. Nevertheless the results suggest this is an important area for future work. While acknowledging a probable publication bias, the findings to date do suggest that a number of psychosocial factors, in particular patients' beliefs about acupuncture, predict treatment outcomes in acupuncture for pain to a significant extent. There is a considerable gap between the psychosocial factors implicated in outcomes by theoretical frameworks and qualitative studies and those factors that have been studied in the context of quantitative RCTs and observational studies. In particular there needs to be a greater focus in quantitative studies on examining the role of factors related to the practitioner and the therapeutic relationship. Overall theory driven, well-powered multivariate studies which incorporate well-validated measures carried out in everyday clinical practice are needed to further advance our understanding of the factors that predict outcome from acupuncture. Until the evidence-base in this area is improved it will be impossible to derive concrete recommendations for clinical practice. Instead we make the much more tentative suggestion that a focus on certain psychosocial factors has the potential to enhance patient outcomes; the circumstantial evidence for this is now growing and further research is needed in this area. In particular we would advocate that practitioners develop an improved awareness of the potential impact of patients' outcome expectations as well as a positive therapeutic relationship.

Fig 1.

Figure 1.Psychosocial factors that should be considered as potential predictors of outcome in acupuncture for pain (according to relevant theory and qualitative findings).
Journal of Acupuncture and Meridian Studies 2008; 1: 1-12https://doi.org/10.1016/S2005-2901(09)60001-7

Table. A comparison of the strengths of using randomized controlled trials (RCTs) and observational designs to investigate predictors of acupuncture outcomes.

Strengths of RCT designsStrengths of observational designs
More control over the treatment and to an extent the practitioner (increasing the homogeneity of both)Greater external, or ecological, validity: patient and practitioner beliefs are more similar to those encountered in everyday practice, therapeutic relationship factors are more similar to those encountered in everyday practice, patients are more similar to those encountered in everyday practice (e.g., not just attending and being treated for one condition)
More “captive audience” (participants who are already involved in the research and who can complete additional measures of psychosocial factors relatively easily, although this might be considered overly burdensome for them)
Established procedures for outcomes assessment (less burdensome for researchers)
Established inclusion and exclusion criteria for patients (increasing the homogeneity of participants)

References

  1. Breivik H, Collett B, Ventafridda V, Cohen R, Gallacher D. Survey of chronic pain in Europe: prevalence, impact on daily life, and treatment. Eur J Pain 2006;10:287-333.
    Pubmed CrossRef
  2. Burke A, Upchurch DM, Dye C, Chyu L. Acupuncture use in the United States: findings from the National Health Interview Survey. J Altern Complement Med 2006;12:639-48.
    Pubmed CrossRef
  3. Thomas KJ, Nicholl JP, Coleman P. Use and expenditure on complementary medicine in England: a population based survey. Complement Ther Med 2001;9:2-11.
    Pubmed CrossRef
  4. Perry R, Dowrick CF. Complementary medicine and general practice: an urban perspective. Complement Ther Med 2000;8:71-5.
    Pubmed CrossRef
  5. Manheimer E, White A, Berman B, Forys K, Ernst E. Metaanalysis: acupuncture for low back pain. Ann Intern Med 2005;142:651-63.
    Pubmed CrossRef
  6. Thomas KJ, MacPherson H, Thorpe L, Brazier J, Fitter M, Campbell MJ, et al. Randomised controlled trial of a short course of traditional acupuncture compared with usual care for persistent non-specific low back pain. BMJ. doi:10.1136/bmj.38878.907361.7C.
    Pubmed KoreaMed CrossRef
  7. Brinkhaus B, Witt CM, Jena S, Linde K, Streng A, Wagenpfeil S, et al. Acupuncture in patients with chronic low back pain: a randomized controlled trial. Arch Intern Med 2006;166:450-7.
    Pubmed CrossRef
  8. Furlan AD, van Tulder M, Cherkin D, Tsukayama H, Lao L, Koes B, et al. Acupuncture and dry-needling for low back pain: an updated systematic review within the framework of the Cochrane Collaboration. Spine 2005;30:944-63.
    Pubmed CrossRef
  9. White P, Lewith G, Prescott P, Conway J. Acupuncture versus placebo for the treatment of chronic mechanical neck pain: a randomized, controlled trial. Ann Intern Med 2004;141:911-9.
    Pubmed CrossRef
  10. Vas J, Perea-Milla E, Mendez C, Sanchez Navarro C, Leon Rubio JM, Brioso M, et al. Efficacy and safety of acupuncture for chronic uncomplicated neck pain: a randomised controlled study. Pain 2006;126:245-55.
    Pubmed CrossRef
  11. Witt C, Brinkhaus B, Jena S, Linde K, Streng A, Wagenpfeil S, et al. Acupuncture in patients with osteoarthritis of the knee: a randomised trial. Lancet 2005;366:136-43.
    Pubmed CrossRef
  12. Linde K, Streng A, Jurgens S, Hoppe A, Brinkhaus B, Witt C, et al. Acupuncture for patients with migraine: a randomized controlled trial. JAMA 2005;293:2118-25.
    Pubmed CrossRef
  13. Melchart D, Streng A, Hoppe A, Brinkhaus B, Witt C, Wagenpfeil S, et al. Acupuncture in patients with tensiontype headache: randomised controlled trial. BMJ 2005;331:376-82.
    Pubmed KoreaMed CrossRef
  14. Vickers AJ, Rees RW, Zollman CE, McCarney R, Smith CM, Ellis N, et al. Acupuncture for chronic headache in primary care: large, pragmatic, randomised trial. BMJ 2004;328:744.
    Pubmed KoreaMed CrossRef
  15. MacPherson H, Thomas K, Walters S, Fitter M. The York acupuncture safety study: prospective survey of 34,000 treatments by traditional acupuncturists. BMJ 2001;323:486-7.
    Pubmed KoreaMed CrossRef
  16. White A, Hayhoe S, Hart A, Ernst E. Adverse events following acupuncture: prospective survey of 32,000 consultations with doctors and physiotherapists. BMJ 2001;323:485-6.
    Pubmed KoreaMed CrossRef
  17. Ratcliffe J, Thomas KJ, MacPherson H, Brazier J. A randomised controlled trial of acupuncture care for persistent low back pain: cost effectiveness analysis. BMJ. doi: 10.1136/bmj.38932.806134.7C.
    Pubmed KoreaMed CrossRef
  18. Witt CM, Jena S, Selim D, Brinkhaus B, Reinhold T, Wruck K, et al. Pragmatic randomized trial evaluating the clinical and economic effectiveness of acupuncture for chronic low back pain. Am J Epidemiol 2006;164:487-96.
    Pubmed CrossRef
  19. Willich SN, Reinhold T, Selim D, Jena S, Brinkhaus B, Witt CM. Cost-effectiveness of acupuncture treatment in patients with chronic neck pain. Pain 2006;125:107-13.
    Pubmed CrossRef
  20. Wonderling D, Vickers AJ, Grieve R, McCarney R. Cost effectiveness analysis of a randomised trial of acupuncture for chronic headache in primary care. BMJ 2004;328:747.
    Pubmed KoreaMed CrossRef
  21. Kirsch I, Sapirstein G. Listening to prozac but hearing placebo: a meta-analysis of antidepressant medication. Prev Treat 1998;1:2a. doi:10.1037/1522-3736.1.1.12a.
    CrossRef
  22. Wampold BE, Minami T, Tierney SC, Baskin TW, Bhati KS. The placebo is powerful: estimating placebo effects in medicine and psychotherapy from randomized clinical trials. J Clin Psychol 2005;61:835-54.
    Pubmed CrossRef
  23. McCracken LM, Turk DC. Behavioral and cognitive-behavioral treatment for chronic pain: outcome, predictors of outcome, and treatment process. Spine 2002;27:2564-73.
    Pubmed CrossRef
  24. Burton AK, Tillotson KM, Main CJ, Hollis S. Psychosocial predictors of outcome in acute and subchronic low back trouble. Spine 1995;20:722-8.
    Pubmed CrossRef
  25. Wessels T, van Tulder M, Sigl T, Ewert T, Limm H, Stucki G. What predicts outcome in non-operative treatments of chronic low back pain? A systematic review. Eur Spine J 2007;15:1633-44.
    Pubmed CrossRef
  26. Kaptchuk TJ. The placebo effect in alternative medicine: can the performance of a healing ritual have clinical significance? Ann Intern Med 2002;136:817-25.
    Pubmed CrossRef
  27. Stewart-Williams S, Podd J. The placebo effect: dissolving the expectancy versus conditioning debate. Psychol Bull 2004;130:324-40.
    Pubmed CrossRef
  28. Kirsch I. Response expectancy theory and application: a decennial review. Appl Prev Psychol 1997;6:69-79.
    CrossRef
  29. Benedetti F, Pollo A, Lopiano L, Lanotte M, Vighetti S, Rainero I. Conscious expectation and unconscious conditioning in analgesic, motor, and hormonal placebo/nocebo responses. J Neurosci 2003;23:4315-23.
    Pubmed KoreaMed CrossRef
  30. Kirsch I. Conditioning, expectancy, and the placebo effect: comment on Stewart-Williams and Podd (2004). Psychol Bull 2004;130:341-3.
    Pubmed CrossRef
  31. Price DD, Milling LS, Kirsch I, Duff A, Montgomery GH, Nicholls SS. An analysis of factors that contribute to the magnitude of placebo analgesia in an experimental paradigm. Pain 1999;83:147-56.
    Pubmed CrossRef
  32. Mondloch MV, Cole DC, Frank JW. Does how you do depend on how you think yoúll do? A systematic review of the evidence for a relation between patients' recovery expectations and health outcomes. CMAJ 2001;165:174-9.
  33. Vlaeyen JWS, Kole-Snijders AMJ, Boeren RGB, van Eek H. Fear of movement/(re)injury in chronic low back pain and its relation to behavioral performance. Pain 1995;62:363-72.
    Pubmed CrossRef
  34. Vlaeyen JWS, Linton SJ. Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art. Pain 2000;85:317-32.
    Pubmed CrossRef
  35. Dionne CE, Koepsell TD, Von Korff M, Deyo RA, Barlow WE, Checkoway H. Predicting long-term functional limitations among back pain patients in primary care settings. J Clin Epidemiol 1997;50:31-43.
    Pubmed CrossRef
  36. Hildebrandt J, Pfingsten M, Saur P, Jansen J. Prediction of success from a multidisciplinary treatment program for chronic low back pain. Spine 1997;22:990-1001.
    Pubmed CrossRef
  37. Jellema P, van der Horst HE, Vlaeyen JWS, Stalman WAB, Bouter LM, van der Windt DAWM. Predictors of outcome in patients with (sub)acute low back pain differ across treatment groups. Spine 2006;31:1699-705.
    Pubmed CrossRef
  38. Smeets RJEM, Vlaeyen JWS, Kester ADM, Knottnerus JA. Reduction of pain catastrophizing mediates the outcome of both physical and cognitive-behavioral treatment in chronic low back pain. J Pain 2006;7:261-71.
    Pubmed CrossRef
  39. Boersma K, Linton SJ. Expectancy, fear and pain in the prediction of chronic pain and disability: a prospective analysis. Eur J Pain 2006;10:551-7.
    Pubmed CrossRef
  40. Dionne CE, Bourbonnais R, Fremont P, Rossignol M, Stock SR, Nouwen A, et al. Determinants of "return to work in good health" among workers with back pain who consult in primary care settings: a 2-year prospective study. Eur Spine J 2007;16:641-55.
    Pubmed KoreaMed CrossRef
  41. Swinkels-Meewisse IEJ, Roelofs J, Schouten EGW, Verbeek ALM, Oostendorp RAB, Vlaeyen JWS. Fear of movement/(re)injury predicting chronic disabling low back pain: a prospective inception cohort study. Spine 2006;31:658-64.
    Pubmed CrossRef
  42. Poiraudeau S, Rannou F, Le Henanff A, Coudeyre E, Rozenberg S, Huas D, et al. Outcome of subacute low back pain: influence of patients' and rheumatologists' characteristics. Rheumatology (Oxford) 2006;45:718-23.
    Pubmed CrossRef
  43. Mannion AF, Junge A, Taimela S, Muntener M, Lorenzo K, Dvorak J. Active therapy for chronic low back pain. Part 3. Factors influencing self-rated disability and its change following therapy. Spine 2001;26:920-9.
    Pubmed CrossRef
  44. Woby SR, Watson PJ, Roach NK, Urmston M. Are changes in fear-avoidance beliefs, catastrophizing, and appraisals of control, predictive of changes in chronic low back pain and disability? Eur J Pain 2004;8:201-10.
    Pubmed CrossRef
  45. George SZ, Bialosky JE, Donald DA. The centralization phenomenon and fear-avoidance beliefs as prognostic factors for acute low back pain: a preliminary investigation involving patients classified for specific exercise. J Orthop Sports Phys Ther 2005;35:580-8.
    Pubmed CrossRef
  46. Altmaier EM, Russell DW, Kao CF, Lehmann TR, Weinstein JN. Role of self-efficacy in rehabilitation outcome among chronic low back pain patients. J Couns Psychol 1993;40:335-9.
    CrossRef
  47. Asante AK, Brintnell ES, Gross DP. Functional self-efficacy beliefs influence functional capacity evaluation. J Occup Rehabil 2007;17:73-82.
    Pubmed CrossRef
  48. Lackner JM, Carosella AM. The relative influence of perceived pain control, anxiety, and functional self efficacy on spinal function among patients with chronic low back pain. Spine 1999;24:2254-60.
    Pubmed CrossRef
  49. Horne R. Representations of medication and treatment: advances in theory and measurement. In: Petrie KJ, Weinman JA, editors. Perceptions of Health and Illness. Amsterdam: Harwood Academic Publishers, 1997:155-88.
  50. Leventhal HA, Brissette I, Leventhal EA. The common-sense model of self-regulation of health and illness. In: Cameron LD, Leventhal H, editors. The Self-regulation of Health and Illness Behaviour. London: Routledge, 2003:42-65.
  51. Hagger MS, Orbell S. A meta-analytic review of the common-sense model of illness representations. Psychol Health 2003;18:141-84.
    CrossRef
  52. Grotle M, Vollestad NK, Veierod MB, Brox JI. Fear-avoidance beliefs and distress in relation to disability in acute and chronic low back pain. Pain 2004;112:343-52.
    Pubmed CrossRef
  53. Gheldof ELM, Vinck J, Van den Bussche E, Vlaeyen JWS, Hidding A, Crombez G. Pain and pain-related fear are associated with functional and social disability in an occupational setting: evidence of mediation by pain-related fear. Eur J Pain 2006;10:513-25.
    Pubmed CrossRef
  54. Koleck M, Mazaux JM, Rascle N, Bruchon-Schweitzer M. Psycho-social factors and coping strategies as predictors of chronic evolution and quality of life in patients with low back pain: a prospective study. Eur J Pain 2006;10:1-11.
    Pubmed CrossRef
  55. Di Blasi Z, Harkness E, Ernst E, Georgiou A, Kleijnen J. Influence of context effects on health outcomes: a systematic review. Lancet 2001;357:757-62.
    Pubmed CrossRef
  56. Di Blasi Z, Kleijnen J. Context effects. Powerful therapies or methodological bias? Eval Health Prof 2003;26:166-79.
    Pubmed CrossRef
  57. Cassidy CM. Chinese medicine users in the United States. Part II. Preferred aspects of care. J Altern Complement Med 1998;4:189-202.
    Pubmed CrossRef
  58. Gould A, MacPherson H. Patient perspectives on outcomes after treatment with acupuncture. J Altern Complement Med 2001;7:261-8.
    Pubmed CrossRef
  59. Griffiths V, Taylor B. Informing nurses of the lived experience of acupuncture treatment: a phenomenological account. Complement Ther Clin Pract 2005;11:111-20.
    Pubmed CrossRef
  60. MacPherson H, Thorpe L, Thomas K. Beyond needling⎯ therapeutic processes in acupuncture care: a qualitative study nested within a low-back pain trial. J Altern Complement Med 2006;12:873-80.
    Pubmed CrossRef
  61. Paterson C, Britten N. Acupuncture as a complex intervention: a holistic model. J Altern Complement Med 2004;10:791-801.
    Pubmed CrossRef
  62. Walker G, de Valois B, Young T, Davies R, Maher J. The experience of receiving traditional Chinese acupuncture: a qualitative study involving women with breast cancer having treatment for the menopausal symptoms associated with tamoxifen. Eur J Orient Med 2004;4:59-65.
  63. Bernstein KS. The experience of acupuncture for treatment of substance dependence. J Nurs Scholarsh 2000;32:267-72.
    Pubmed CrossRef
  64. Richardson J. What patients expect from complementary therapy: a qualitative study. Am J Public Health 2004;94:1049-53.
    Pubmed KoreaMed CrossRef
  65. Kong J, Gollub R, Huang T, Polich G, Napadow V, Hui K, et al. Acupuncture de qi, from qualitative history to quantitative measurement. J Altern Complement Med 2007;13:1059-70.
    Pubmed CrossRef
  66. Hughes JG, Goldbart J, Fairhurst E, Knowles K. Exploring acupuncturists' perceptions of treating patients with rheumatoid arthritis. Complement Ther Med 2007;15:101-8.
    Pubmed CrossRef
  67. Ballegaard S, Karpatschoff B, Holck JA, Meyer CN, Trojaborg W. Acupuncture in angina pectoris: do psycho-social and neurophysiological factors relate to the effect? Acupunct Electrother Res 1995;20:101-16.
    Pubmed CrossRef
  68. Chae Y, Park HJ, Hahm DH, Yi SH, Lee H. Individual differences of acupuncture analgesia in humans using cDNA microarray. J Physiol Sci 2006;56:425-31.
    Pubmed CrossRef
  69. Choi PYL, Tweed A. The holistic approach in acupuncture treatment: implications for clinical trials. J Psychosom Res 1996;41:349-56.
    Pubmed CrossRef
  70. Margolin A, Avants SK, Holford TR. Interpreting conflicting findings from clinical trials of auricular acupuncture for cocaine addiction: does treatment context influence outcome? J Altern Complement Med 2002;8:111-21.
    Pubmed CrossRef
  71. Norton GR, Goszer L, Strub H, Man SC. The effects of belief on acupuncture analgesia. Can J Behav Sci 1984;16:22-9.
    CrossRef
  72. Roscoe JA, Morrow GR, Hickok JT, Bushunow P, Pierce HI, Flynn PJ, et al. The efficacy of acupressure and acustimulation wrist bands for the relief of chemotherapy-induced nausea and vomiting. A University of Rochester Cancer Center Community Clinical Oncology Program multicenter study. J Pain Symptom Manage 2003;26:731-42.
    Pubmed CrossRef
  73. Schneider A, Enck P, Streitberger K, Weiland C, Bagheri S, Witte S, et al. Acupuncture treatment in irritable bowel syndrome. Gut 2006;55:649-54.
    Pubmed KoreaMed CrossRef
  74. Schneider A, Lowe B, Streitberger K. Perception of bodily sensation as a predictor of treatment response to acupuncture for postoperative nausea and vomiting prophylaxis. J Altern Complement Med 2005;11:119-25.
    Pubmed CrossRef
  75. Kalauokalani D, Cherkin DC, Sherman KJ, Koepsell TD, Deyo RA. Lessons from a trial of acupuncture and massage for low back pain. Spine 2001;26:1418-24.
    Pubmed CrossRef
  76. Linde K, Witt CM, Streng A, Weidenhammer W, Wagenpfeil S, Brinkhaus B, et al. The impact of patient expectations on outcomes in four randomized controlled trials of acupuncture in patients with chronic pain. Pain 2007;128:264-71.
    Pubmed CrossRef
  77. Harborow PW, Ogden J. The effectiveness of an acupuncturist working in general practice: an audit. Acupunct Med 2004;22:214-20.
    Pubmed CrossRef
  78. Meng CF, Wang D, Ngeow J, Lao L, Peterson M, Paget S. Acupuncture for chronic low back pain in older patients: a randomized, controlled trial. Rheumatology (Oxford) 2003;42:1508-17.
    Pubmed CrossRef
  79. Bausell RB, Lao L, Bergman S, Lee WL, Berman BM. Is acupuncture analgesia an expectancy effect? Preliminary evidence based on participants' perceived assignments in two placebo-controlled trials. Eval Health Prof 2005;28:9-26.
    Pubmed CrossRef
  80. Birch S, Jamison RN. Controlled trial of Japanese acupuncture for chronic myofascial neck pain: assessment of specific and nonspecific effects of treatment. Clin J Pain 1998;14:248-55.
    Pubmed CrossRef
  81. Lao L, Bergman S, Hamilton GR, Langenberg P, Berman B. Evaluation of acupuncture for pain control after oral surgery: a placebo-controlled trial. Arch Otolaryngol Head Neck Surg 1999;125:567-72.
    Pubmed CrossRef
  82. Baischer W. Acupuncture in migraine: long-term outcome and predicting factors. Headache 1995;35:474.
    Pubmed CrossRef
  83. MacPherson H, Mercer SW, Scullion T, Thomas KJ. Empathy, enablement, and outcome: an exploratory study on acupuncture patients' perceptions. J Altern Complement Med 2003;9:869-76.
    Pubmed CrossRef
  84. So DW. Acupuncture outcomes, expectations, patient- provider relationship, and the placebo effect: implications for health promotion. Am J Public Health 2002;92:1662-7.
    Pubmed KoreaMed CrossRef
  85. Lu DP, Lu GP, Kleinman L. Acupuncture and clinical hypnosis for facial and head and neck pain: a single crossover comparison. Am J Clin Hypn 2001;44:141-8.
    Pubmed CrossRef
  86. Kreitler S, Kreitler H, Carasso R. Cognitive orientation as predictor of pain relief following acupuncture. Pain 1987;28:323-41.
    Pubmed CrossRef
  87. Toomey TC, Ghia JN, Mao W, Gregg JM. Acupuncture and chronic pain mechanisms: the moderating effects of affect, personality, and stress on response to treatment. Pain 1977;3:137-45.
    Pubmed CrossRef
  88. Creamer P, Singh BB, Hochberg MC, Berman BM. Are psychosocial factors related to response to acupuncture among patients with knee osteoarthritis? Altern Ther Health Med 1999;5:72-6.
    Pubmed
  89. Tavola T, Gala C, Conte G, Invernizzi G. Traditional Chinese acupuncture in tension-type headache: a controlled study. Pain 1992;48:325-9.
    Pubmed CrossRef
  90. Karst M, Reinhard M, Thum P, Wiese B, Rollnik J, Fink M. Needle acupuncture in tension-type headache: a randomized, placebo-controlled study. Cephalalgia 2001;21:637-42.
    Pubmed CrossRef
  91. Weidenhammer W, Linde K, Streng A, Hoppe A, Melchart D. Acupuncture for chronic low back pain in routine care: a multicenter observational study. Clin J Pain 2007;23:128-35.
    Pubmed CrossRef
  92. Zaretsky HH, Lee MHM, Rubin M. Psychological factors and clinical observations in acupuncture analgesia and pain abatement. J Psychol 1976;93:113-20.
    Pubmed CrossRef
  93. Wylie KR, Jackson C, Crawford PM. Does psychological testing help to predict the response to acupuncture or massage/relaxation therapy in patients presenting to a general neurology clinic with headache? J Tradit Chin Med 1997;17:130-139.
    Pubmed
  94. Berk SN, Moore ME, Resnick JH. Psychosocial factors as mediators of acupuncture therapy. J Consult Clin Psychol 1977;45:612-9.
    Pubmed CrossRef
  95. Price S, Mercer SW, MacPherson H. Practitioner empathy, patient enablement and health outcomes: a prospective study of acupuncture patients. Patient Educ Couns 2006;63:239-45.
    Pubmed CrossRef
  96. Weidenhammer W, Streng A, Linde K, Hoppe A, Melchart D. Acupuncture for chronic pain within the research program of 10 German Health Insurance Funds: basic results from an observational study. Complement Ther Med 2007;15:238-46.
    Pubmed CrossRef
  97. McManus CA, Kaptchuk TJ, Schnyer RN, Goldman R, Kerr CE, Nguyen LT, et al. Experiences of acupuncturists in a placebo-controlled, randomized clinical trial. J Altern Complement Med 2007;13:533-8.
    Pubmed CrossRef
  98. Stone DA, Kerr CE, Jacobson E, Conboy LA, Kaptchuk TJ. Patient expectations in placebo-controlled randomized clinical trials. J Eval Clin Pract 2005;11:77-84.
    Pubmed CrossRef
  99. von Elm E, Altman DG, Egger M, Pocock SJ, Gotzsche PC, Vandenbroucke JP, et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Ann Intern Med 2007;147:573-7.
    Pubmed CrossRef
  100. Karjalainen K, Malmivaara A, Mutanen P, Pohjolainen T, Roine R, Hurri H. Outcome determinants of subacute low back pain. Spine 2003;28:2634-40.
    Pubmed CrossRef
  101. Bekkering GE, Hendriks HJM, van Tulder MW, Knol DL, Simmonds MJ, Oostendorp RA, et al. Prognostic factors for low back pain in patients referred for physiotherapy: comparing outcomes and varying modeling techniques. Spine 2005;30:1881-6.
    Pubmed CrossRef
  102. Jones GT, Johnson RE, Wiles NJ, Chaddock C, Potter RG, Roberts C, et al. Predicting persistent disabling low back pain in general practice: a prospective cohort study. Br J Gen Pract 2006;56:334-41.
    Pubmed KoreaMed
  103. Skargren EI, Oberg BE. Predictive factors for 1-year outcome of low-back and neck pain in patients treated in primary care: comparison between the treatment strategies chiropractic and physiotherapy. Pain 1998;77:201-7.
    Pubmed CrossRef
  104. Leboeuf-Yde C, Gronstvedt A, Borge JA, Lothe J, Magnesen E, Nilsson O, et al. The Nordic back pain subpopulation program: demographic and clinical predictors for outcome in patients receiving chiropractic treatment for persistent low-back pain. J Manipulative Physiol Ther 2004;27:493-502.
    Pubmed CrossRef
  105. Groth-Marnat G, Fletcher A. Influence of neuroticism, catastrophizing, pain duration, and receipt of compensation on short-term response to nerve block treatment for chronic back pain. J Behav Med 2000;23:339-350.
    Pubmed CrossRef
  106. White PJ. Attitude and outcome, is there a link in complementary medicine? Am J Public Health 2003;93:1038.
    Pubmed KoreaMed CrossRef
  107. Dworkin RH, Turk DC, Farrar JT, Haythornthwaite JA, Jensen MP, Katz NP, et al. Core outcome measures for chronic pain clinical trials: IMMPACT recommendations. Pain 2005;113:9-19.
    Pubmed CrossRef
  108. Devilly GJ, Borkovec TD. Psychometric properties of the credibility/expectancy questionnaire. J Behav Ther Exp Psychiatry 2000;31:73-86.
    Pubmed CrossRef
  109. Mao JJ, Armstrong K, Farrar JT, Bowman MA. Acupuncture expectancy scale: development and preliminary validation in China. Explore (NY) 2007;3:372-7.
    Pubmed KoreaMed CrossRef
  110. Vincent C. Credibility assessment in trials of acupuncture. Complement Med Res 1990;4:8-11.
  111. Paterson C, Dieppe P. Characteristic and incidental (placebo) effects in complex interventions such as acupuncture. BMJ 2005;330:1202-5.
    Pubmed KoreaMed CrossRef