2 Evidence-Based Complementary and Alternative Medicinefor assessing acupuncture. This would suggest that a lack of et al.  cite following placebo acupuncture do not dis-diﬀerence between real and placebo acupuncture in RCTs count the possibility of expectancy eﬀects. There is alsomay result from the omission of important components of evidence that the more invasive the placebo, the larger theacupuncture, such as facilitating patients active involvement placebo eﬀect. For example, four placebo pills reduced recov-in their recovery and lifestyle advice, that is common in ery times from duodenal ulcers compared with two placebothese trials [6, 11]. However, before such a conclusion can pills  and a subcutaneous placebo injection reduced painbe drawn, evidence is required that demonstrates a larger due to migraine headaches more eﬀectively than a placebobeneﬁt of providing acupuncture treatment than summing pill . As such, placebo acupuncture may simply producethe beneﬁt of providing the individual components of acu- stronger expectancy eﬀects than placebo pills do. Finally, ifpuncture alone, which, to our knowledge, has not yet been both real and placebo acupuncture exert their eﬀects as atested. result of expectancy, then this would lead to frequent null Placebo (or sham) controls adopted in RCTs of acupunc- diﬀerences and occasional statistically signiﬁcant diﬀerencesture include needle insertion at nonacupuncture points between the two treatments caused by sampling variation (cf.(sham acupuncture), shallow needle insertion that does not Type I error ), including placebo acupuncture appearingpenetrate below the skin (minimal or superﬁcial needling), superior to real acupuncture on occasion As a result, there isand blunt needles that touch, but do not penetrate the skin as yet no conclusive evidence that the currently used placebo(placebo needling). Lundeberg and colleagues [12–14] have controls are active beyond expectancy.argued that these techniques are not inert and are, therefore, Perhaps more importantly, the three alternative explana-invalid as placebo controls. They provide a list of eleven tions for the common lack of statistically signiﬁcant diﬀer-reasons why the placebo controls used in acupuncture RCTs ences between real and placebo acupuncture are not mutu-may be active treatments, including evidence of physiological ally exclusive. Needling may be more eﬃcacious when deliv-responses to sham acupuncture, evidence that superﬁcial and ered with lifestyle advice, but this does not mean thatsham needling producing larger eﬀects than a placebo pill, patients’ expectancies about the eﬃcacy of an acupunc-and, rather strangely, that placebo controls can be as eﬀective ture intervention cannot inﬂuence their outcomes via theor even more eﬀective than real acupuncture. placebo eﬀect. Similarly, currently used placebo controls for However, the evidence provided by Lundeberg et al.  acupuncture needling could be invalid, but this does notcan be explained equally well in the context of patient ex- preclude the possibility that expectancies could contribute topectancies. Expectancy is proposed to be a key mechanism of responses to real acupuncture. As demonstrated by Benedettithe placebo eﬀect. Placebo eﬀects are changes that occur in et al. , most medical treatments, whether eﬃcacious orresponse to receiving treatment but that are not due to the not, appear to be inﬂuenced by patient expectancies. Thus,inherent properties of the treatment itself . Many studies regardless of whether or not the combined eﬀects of anhave found that a saline injection or placebo cream admin- acupuncture intervention cannot be explained by the eﬀectsistered under the guise of a powerful analgesic can, in fact, of each component’s individual eﬃcacy or whether or notreduce pain, for example [16–22]. There is also evidence for the currently used placebo controls in acupuncture RCTs areplacebo eﬀects across a range of other conditions (see  for valid, it remains important to establish both if and how thea recent review). For example, placebo treatment appears to placebo eﬀect contributes to responses to acupuncture.reduce depressive symptoms , improve sleep quality  With this in mind, we conducted a systematic review ofimprove motor performance in patients with Parkinson’s the literature to examine whether expectancies can inﬂuencedisease , modulate heat rate in healthy volunteers , acupuncture outcomes. Although we had intended to useand improve cognitive performance in healthy volunteers meta-analysis to estimate and test the magnitude of the eﬀect. Perhaps most interestingly, Benedetti et al.  found of expectancy on treatment responses following acupunc-signiﬁcantly larger treatment eﬀects for postoperative pain, ture, the studies identiﬁed were too heterogeneous withmotor performance in patients with Parkinson’s disease, and respect to methodology and reporting to allow such analysis.heart rate in healthy participants when the initiation of We, therefore, provide a descriptive review of studies inves-treatment was signalled to the patient by a health profes- tigating placebo eﬀects in acupuncture, drawing particularsional compared with when it was initiated surreptitiously attention to methodological considerations, and outlinewithout the patients’ awareness, indicating that most medical some key goals for future research in this area.treatments involve a placebo component. On this basis, someresearchers have argued that the superiority of both realand placebo acupuncture techniques over no treatment (or 2. Methodsin some cases standard care) combined with failure to ﬁndsigniﬁcant diﬀerences between real and placebo acupuncture 2.1. Search Strategy. Articles were identiﬁed through com-can be explained by the placebo eﬀect [28, 29]. That is, puterized literature searches. Medline, PsycInfo, PubMed,they argue that any improvement following acupuncture and Cochrane Clinical Trials Register were searched fortreatment, whether real or placebo, results from the patients English publications from inception up to 1st December,expecting acupuncture to be eﬀective. 2010 using the search terms “expectancy OR expectancies If expectancies do lead to real changes in symptoms via OR expectation$ OR expected eﬃcacy OR placebo eﬀect$”the placebo eﬀect, then physiological changes must underlie in combination with “acupuncture” using title and abstractthese eﬀects. Therefore, the physiological changes Lundeberg ﬁelds. The reference lists of publications identiﬁed through
Evidence-Based Complementary and Alternative Medicine 3the electronic search were also screened for additional rele- Records identiﬁed throughvant articles. database searches: Cochrane CCTR (n = 75) Medline (n = 151)2.2. Selection Criteria. To be included, studies needed to PsychInfo (n =59)either assess or manipulate participants’ expectancies regard- PubMed (n = 107)ing the eﬃcacy of an acupuncture intervention involving Total: 392needling and to report on the relationship between theseexpectancies or the manipulation and at least one outcome Duplicates removed (n = 191)variable. The acupuncture intervention could include man-ual or electroacupuncture and could be standardised or Records screenedindividualised. Assessing expectancies regarding the eﬃcacy (n = 201)of acupuncture involved any question asking participantsto rate their expectancies for improvement as a result of Records excluded (n = 184)acupuncture but had to be prospective; that is, the ex-pectancy assessment had to occur before the acupuncture Full-text articles assessedtreatment. Manipulating expectancies meant allocating par- independently for eligibilityticipants to receive diﬀerent information about the likely (n = 17)eﬀects of their treatment, whether real or placebo acupunc- Records excluded because:ture was delivered. For example, Suarez-Almazor et al.  methodological concerns (n = 5) data reported elsewhere (n = 3)randomly allocated participants in a RCT comparing real andsham acupuncture for osteoarthritis of the knee to receive Studies included in qualitativesuggestion from the acupuncturist that either the treatment synthesis“will work” (high expectancy) or that it “may or may not (n = 9)work” (low expectancy). Studies investigating both clinicaland nonclinical conditions (e.g., experimentally-induced Figure 1: Flow diagram for study identiﬁcation and selection.pain) were included. The studies could assess any health-related outcome, whether subjective or objective, and therewere no constraints on study design, as long as the criteria for expectancies retrospectively in the form of guesses aboutassessing and/or manipulating expectancies were met. Only treatment allocation . One was excluded because it failedpeer-reviewed publications in English were included. to directly test the eﬀect of its expectancy manipulation .2.3. Study Selection. One author (B. Colagiuri) conducted 2.4. Data Extraction. The authors reviewed the retrievedthe initial search and excluded articles that were clearly not articles and independently extracted information on samplerelevant. Both authors then reviewed the full texts of each of characteristics, study design, outcome variables, relevantthe remaining articles and evaluated them against the selec- results, and whether the study fulﬁlled the inclusion criteriation criteria independently. Any disagreements were resolved using pre-deﬁned coding sheets. The sample characteristicsthrough discussion. included sample size, proportion of female participants, and The literature search identiﬁed a total of nine indepen- whether the participants had previously used acupuncture.dent studies reporting on the relationship between expect- Study design included the experimental design, charac-ancy and treatment response following acupuncture suitable teristics of the acupuncture treatment that was delivered,for inclusion. Figure 1 displays the ﬂow diagram for study and how expectancies were either assessed or manipulated.selection. The search of Medline, PsycInfo, PubMed, and Study outcomes involved all outcomes that were analysedCochrane Clinical Trials Register provided a total of 392 for relationships with expectancy and were classiﬁed intoEnglish references. After removing duplicates, there were 201 either self-report or objective outcomes. Diﬀerences werearticles, of which 184 were clearly not relevant. The full texts discussed, and a ﬁnal assessment was negotiated for eachof the remaining 17 articles were reviewed independently by study. The PRISMA guidelines for reporting of systematicboth authors. Of these, three articles were excluded because reviews and meta-analyses were followed [41, 42].their results were reported in other articles already identiﬁed[34–36]. This left 14 unique studies. One article was excluded 2.5. Risk of Bias Assessment. Scoring studies numericallybecause it reported on the relationship between expectancy based on their quality is controversial. This is because com-and acupuncture combined with expectancy and an exercise bining quality items into a single score is questionable, par-intervention . One article was excluded because no ticularly in terms of whether or not these items are additivedetails of the expectancy assessment were provided . One [43, 44], and because there is evidence that currently usedwas excluded because it focused on patients with psycho- quality scores do not actually predict variance in eﬀect sizeslogical comorbidity , which although not an a priori [45, 46]. We, therefore, chose not to attribute quality scoresexclusion criteria, both authors agreed might aﬀect the re- to the included studies. Instead, we conducted a risk oflationship between expectancy and treatment outcomes. bias assessment using the Cochrane Collaborations tool forOne was excluded because it only assessed participants’ assessing risk of bias , which includes six dimensions,
4 Evidence-Based Complementary and Alternative Medicinenamely, adequate sequence generation, allocation conceal- the studies with some studies ﬁnding evidence suggestive ofment, blinding, incomplete data, selective reporting, and an interaction [49, 52, 53] and others failing to ﬁnd suchother forms of bias. Both authors completed the risk of evidence [33, 54]. Interaction eﬀects were either not reportedbias assessment for each study independently, with any dis- [48, 51, 55] or not relevant (because only one acupuncturecrepancies resolved through discussion. treatment was administered ) in the remaining studies. No study found evidence of signiﬁcant eﬀects of expectancy2.6. Data Analysis. Meta-analysis of the studies was not pos- on objective outcomes following acupuncture; however, onlysible due a combination of heterogeneous methodology used three studies included objective outcome variables [33, 48,across studies and incomplete reporting of results in some 55].studies. Study results were considered statistically signiﬁcant There were some patterns in terms of the study char-if P < 0.05. acteristics and whether or not a signiﬁcant relationship between expectancy and acupuncture outcomes was found. All three studies investigating experimentally-induced pain3. Results found evidence of a signiﬁcant relationship [52–54], whereas only two of the six studies investigating clinical outcomes3.1. Study Characteristics. A summary of the characteristics found evidence of a signiﬁcant relationship [49, 51]. Threeof the nine studies we identiﬁed is provided in Table 1. The of the four studies that manipulated expectancies foundmajority of studies were on pain-related conditions, both evidence of a signiﬁcant relationship [33, 52, 54], whereasclinical [33, 48–51] and experimentally-induced [52–54]. only one of the ﬁve studies that assessed expectancies foundOne study focused on angina pectoris . In six of the evidence of a signiﬁcant relationship . Four of the ﬁvestudies, participants were acupuncture naive [33, 48, 51– studies involving electroacupuncture found evidence of a54], in two studies, participants had not previously received signiﬁcant relationship between expectancies and treatmentacupuncture for the condition being treated [50, 55], and response [33, 52–54], whereas only one out of the fourin one study no information was provided on participants’ studies involving manual acupuncture found evidence ofprevious use of acupuncture . Electro acupuncture was such a relationship . A high degree of caution is, however,used in ﬁve studies [33, 52–55], manual acupuncture was necessary when attempting to generalise from these patternsused in three studies [48, 49, 51], and one study only as simple vote counting, that is, summing and comparing theinvestigated placebo acupuncture . Five of the studies number of signiﬁcant results with the number of nonsigniﬁ-assessed expectancies [49–51, 53, 55], four manipulated cant results, is associated with a number of problems . Inexpectancies [33, 48, 52, 54]. Assessing expectancies gener- the current case, for example, even though only two of the sixally involved asking participants to rate how eﬀective they studies investigating clinical outcomes found evidence of aexpected acupuncture to be for improving their condition signiﬁcant relationship between expectancy and acupunctureon Likert-type scales. In the majority of studies assessing outcomes [33, 49], these were the two largest in termsexpectancies, participants were either dichotomised into of sample size and likely had the most statistical power.high and low expectancies [49, 53, 55] or trichotomised The same applies to the only study ﬁnding a signiﬁcantinto high, medium, or low expectancies . Manipulating relationship that assessed expectancies . It is also worthexpectancies typically involved randomising participants to noting that studies with healthy volunteers in experimentalreceive information aimed at enhancing their expectancies settings should require fewer participants to achieve the samefor improvement following acupuncture or either neutral or power as studies in clinical settings, because the former arenegative information although one study used a conditioning often better able control for potential confounding variablesprocedure . All studies included self-reported outcomes, due to the controlled laboratory setting, which furtherbut three also included objective outcome variables [33, 48, complicates comparison across these studies. Therefore,55]. while it seems clear that expectancies can aﬀect acupuncture outcomes under at least some circumstances, it is diﬃcult to3.2. The Eﬀect of Expectancy on Responses to Acupuncture. identify which circumstances these are and how strong thisTable 2 provides a descriptive summary of each of the nine relationship is from the available evidence.studies’ ﬁndings. The results of the studies were clearlymixed, with some studies ﬁnding at least some evidence of 3.3. Risk of Bias. As shown in Table 3, all but one study a statistically signiﬁcant eﬀect of expectancy on acupuncture had either some risk or an unclear risk of bias on at leastoutcomes [33, 49, 52–54] and others failing to ﬁnd any one of the six dimensions assessed. Speciﬁcally, sequencesuch eﬀects [48, 50, 51, 55]. Interestingly, there were also generation was inadequate in one study  and unclearsome ﬁndings that were suggestive of an interaction between in four studies [48, 53–55]. Allocation concealment was notexpectancy and type of acupuncture (real versus placebo). used in one study  and was unclear in three studiesFor example, Linde et al.  found that the improve- [48, 54, 55]. Participants were blinded to whether or notment in patients classiﬁed as having “high expectancy” they were receiving real or placebo acupuncture in all studies,compared with those classiﬁed as having “low expectancy” but in four studies the blinding of outcome assessors waswas signiﬁcantly more marked in patients receiving real unclear [48, 49, 53, 54]. All studies satisfactorily addressedacupuncture compared with placebo acupuncture. However, incomplete data, and only one had unclear risk regardingevidence of this type of interaction was inconsistent across selective reporting . In terms of other biases, four studies
Table 1: Summary of included studies’ characteristics. Sample TreatmentStudy Design Expectancy Outcome N % Female Previous use Acupuncturea Placebo Acupuncture at LI11, 2 × 2 between-subjects LI4, LI15, GB39, SI9, Noninsertion at the Manipulated—participants randomised design with S10, and M-UE-48 three study acupuncture to receive acupuncture with positive acupuncture (real Objective—Berk et al. times over 3 weeks. points involving milieu suggesting that acupuncture is an versus placebo) and 42 29% No shoulder mobility.(1977)  Needles were manually gently pressing the tip eﬀective therapy or a negative milieu milieu (positive versus Self report—pain. manipulated, but of the needle against suggesting that acupuncture is an negative) as factors on retention time was not the skin. ineﬀective treatment. shoulder pain. reported. 3 × 3 between-subjects As per acupuncture, design with but stimulated study acupuncture (real, Electroacupuncture at points unilaterally on placebo, or none) LI4 and TH5 once for the arm not placed in Manipulated—participants led to expectKnox et al. versus expectancy 20 min unilaterally on the cold pressor. pain relief, no pain relief, or variable Self report—pain 72 50% No(1979)  (positive, negative, or the arm to be placed in A no treatment eﬀects from acupuncture or from lying at 30 sec. Evidence-Based Complementary and Alternative Medicine variable) for the cold pressor. control group lay down for 20 min. experimentally- Sensation not reported. down for 20 min and induced pain (cold did not receive either pressor). treatment. Assessed—expectancy questionnaire Electroacupuncture at RCT of acupuncture comparing treatments (e.g., surgery, LI5, LI11, SI5, and SI8 versus placebo for Insertion 2 cm distal morphine, aspirin, and acupuncture) forNorton et al. once for 15 min experimentally- 24 50% No to study acupuncture relieving pain and then categorised Self Report—pain.(1984)  unilaterally on the arm induced pain (cold points. participants in to high and low to be placed in the cold pressor). expectancy on the basis of this pressor. questionnaire. Assessed—rating of expectancy concerning anti-anginal eﬀects of Objective— acupuncture as “very high expectations”, exercise tolerance; Superﬁcial (shallow) Electroacupuncture LI4 “somewhat high”, “neutral”, “slightly rate pressure insertion outsideBallegaard RCT of acupuncture for 20 mim. Ten negative”, “moderately negative product; Not for heart Chinese meridianset al. (1995) versus placebo for 32 22% treatments over 3 weeks. expectations”, or “don’t know”. These nitroglycerin disease. and not on trigger angina pectoris. De qi and visible muscle scores were dichotomised into either consumption; points with no twitch achieved. maximal expectation consisting of those angina attack rate. stimulation. who responded “very high expectations” Self report—daily and into submaximal expectations for all wellbeing. others responses. 5
6 Table 1: Continued. Sample TreatmentStudy Design Expectancy Outcome a N % Female Previous use Acupuncture Placebo Assessed—(a) “How eﬀective do you consider acupuncture in general?” and could respond “very eﬀective”, “eﬀective”, Pooled analysis of 4 Superﬁcial needling at Acupuncture protocol “slightly eﬀective”, “not eﬀective”, or Self report—50% RCTs of acupuncture nonacupuncture speciﬁc to RCT, but all “don’t know”. (b) “What do you improvement in versus placebo for points (relevant toLinde et al. were treated once per personally expect from the acupuncture primary outcome migraine, headaches, 864 75% Not stated. each RCT) also once(2007)  week for 12 weeks and you will receive?” and could respond related to trial back pain, and per week for 12 weeks each session lasted “cure”, “clear improvement”, “slight condition; pain osteoarthritis of the and each session 30 min. improvement”, “no improvement”, “don’t disability index. knee. lasting 30 min. know”. Dichotomised into high expectancy (top two responses) versus low expectancy (all other responses). Streitberger placebo Comparison of placebo needles twice per acupuncture versus Not for arm Assessed—“rate how intense you think week for 2 weeks atBertisch et al. placebo pill within a pain and not the pain or discomfort will be 2 weeks 60 53% N/A between 5–10 sites Self report—pain.(2009)  larger RCT for distal within last from now if you are assigned to and unilaterally or upper arm pain due to year. acupuncture” 5-point scale. bilaterally depending RSI. on the patients pain. 2 × 2 between-subjects Streiberger placebo Manipulated—participants given design with needles placed on the stimulation of pain with intensity acupuncture (real surface of the skin at surreptitiously manipulated so as toKong versus placebo) and Electroacupuncture at the study provide experience of acupunctureet al. (2009) expectancy (high 48 50% No LI3 and LI4 once for acupuncture points treatment decreasing pain (high Self report—pain.[35, 54] versus low) as factors 25 min. Di qi achieved. and connected to a expectancy) or with intensity identical to for experimentally- deactivated baseline so as to provide experience of induced pain (heat electroacupuncture acupuncture failing to decrease pain (low stimulation). device. expectancy). Evidence-Based Complementary and Alternative Medicine
Table 1: Continued. Sample TreatmentStudy Design Expectancy Outcome N % Female Previous use Acupuncturea Placebo (a) Placebo acupuncture (a) Individualised involving sham acupuncture with points insertion using a and sensation toothpick in a needle determined based on RCT of individualised guide tube as per the patients’ individual acupuncture, standardised Assessed—participants rated how helpful diagnosis. Ten SelfSherman standardised acupuncture, they believed acupuncture would be for treatments in 7 weeks. report—disability;et al. (2010) acupuncture, placebo 477 61% No including their back pain on 11-point scale. (b) Standardised symptom acupuncture, and manipulation via Responses trichotomised into low (0–5), Evidence-Based Complementary and Alternative Medicine acupuncture at B23, bothersomeness. standard care for twisting the tooth medium (6 and 7), and high (8–10). B40, K3 bilaterally and chronic back pain. pick. Du3, main trigger point (b) Standard care was unilaterally for 20 min the usual care with manual stimulation participants received to elicit “de qi”. from their physicians, if any. Electro-acupuncture at 2 × 2 trial with GB34, SP6, SP9, communication style Self report—pain, Ear-Knee, Ex-LE2, Manipulated—participants randomised (positive or negative) satisfaction;Suarez- Ex-LE4, Ex-LE5, and 1-2 to an acupuncturist who communicated and acupuncture (real Shallow insertion at physical andAlmazor trigger points. Needle positive messages about acupuncture, for or placebo) as factors 527 61% No acupoints not mental satisfaction.et al. (2010) retention was 20 min example, “I think this will work for you”, and an additional relevant to the knee. Objective—range and treatment lasted 6 or to neutral communication such as, “It waitlist control group of motion; timed weeks although the may or may not work for you”. for osteoarthritis of the up and go test. number of sessions per knee. week was not reported.a All bilateral acupuncture points stimulated bilaterally unless speciﬁed otherwise. 7
8 Evidence-Based Complementary and Alternative Medicine Table 2: Summary of included studies’ results.Study Expectancy Summary of resultsa There were no signiﬁcant diﬀerences between real and placebo acupuncture. There were also no signiﬁcant diﬀerences on shoulder mobility for those given positive versus negative information aboutBerk et al.  Manipulated acupuncture. Those given positive information reported lower shoulder pain than those given negative information, but this did not reach statistical signiﬁcance (P = 0.053). Interaction between acupuncture and expectancy not reported. There were no signiﬁcant main eﬀects of acupuncture or expectancy. However, posttreatment experimentally-induced pain reduced signiﬁcantly from baseline in participants given real acupuncture with positiveKnox et al. (1979)  Manipulated information but not in participants given real acupuncture with variable or negative information, nor in participants given placebo acupuncture with positive, variable, or negative information. There was a signiﬁcant interaction between acupuncture and expectancy. Simple eﬀects revealed participants receiving real acupuncture reported signiﬁcantly less experimentally-induced pain if they had “highNorton et al. (1984)  Assessed (dichotomised) expectancy” compared with “low expectancy”. Participants with “high expectancy” who received real acupuncture also reported signiﬁcantly less pain than those also with “high expectancy” but who received placebo acupuncture. Main eﬀects of acupuncture and expectancy not reported. There were no signiﬁcant diﬀerences on any angina outcome between participants categorised as having “maximal expectancy” and “submaximalBallegaard et al. (1995)  Assessed (dichotomised) expectancy”. Main eﬀect of acupuncture and its interaction with expectancy not reported. Those receiving real acupuncture were more likely to respond to treatment than those receiving placebo acupuncture. Higher expectancies for acupuncture’s eﬃcacy in general and speciﬁcally for the patients’ presenting condition were associated with a higher likelihood of experiencing a 50% improvement in the studies’ main outcome and aLinde et al. (2007)  Assessed (dichotomised) reduction in pain disability index both immediately posttreatment and at follow up. Signiﬁcant interaction on “some” outcomes indicating the improved outcomes for those with “high expectancy” compared with “low expectancy” were more marked for patients receiving real acupuncture than those receiving placebo acupuncture. No signiﬁcant relationship was found between expectancies and upper armBertisch et al. (2009)  Assessed pain following placebo acupuncture in both unadjusted and multivariate analysis. No main eﬀect of acupuncture. Participants allocated to receive pre-conditioning consistent with acupuncture having an analgesic eﬀect reported signiﬁcantly less experimentally-induced pain followingKong et al. (2009) [35, 54] Manipulated acupuncture than those allocated to receive pre-conditioning of acupuncture having no eﬀect. There was no interaction between acupuncture and expectancy. Individualised, standardised, and placebo acupuncture were more eﬀective at reducing chronic low back pain than usual care, but there were noSherman et al. (2010)  Assessed (trichotomised) signiﬁcant diﬀerences among these three treatments. There were also no signiﬁcant diﬀerences between those with “high”, “medium”, and “low” expectancies. Interaction between treatment and expectancy not reported. No diﬀerences were found between real and placebo acupuncture, but both led to better outcomes compared with the waitlist control group.Suarez-Almazor et al. Participants allocated to receive positive information had signiﬁcantly Manipulated(2010)  lower pain and higher satisfaction than those allocated to receive neutral information and this was independent of whether real or placebo acupuncture was administered.a All results are main eﬀects unless stated otherwise.
Evidence-Based Complementary and Alternative Medicine 9 Table 3: Risk of bias assessment for the included studies. Adequate Allocation Blinding?a Incomplete Free of selectiveStudy sequence Concealment? data Free of other bias? generation? Outcome addressed? reporting bias? Participant AssessorBerk et al. Unclear Unclear Yes Unclear Yes Yes Yes(1977) Knox et al. No No Yes Yes Yes Yes Yes(1979)  No—small sample size forNorton et al. Unclear Yes Yes Unclear Yes Yes correlational study; dichotomised(1984)  expectancy No—small sample size forBallegaard et al. Unclear Unclear Yes Yes Yes Unclear correlational study; dichotomised(1995)  expectancyLinde et al. Yes Yes Yes Unclear Yes Yes No—dichotomised expectancy(2007) Bertisch et al. No—small-medium sample size Yes Yes Yes Yes Yes Yes(2009)  for correlational studyKong et al. Unclear Unclear Yes Unclear Yes Yes Yes(2009) [35, 54]Sherman et al. Yes Yes Yes Yes Yes Yes No—trichotomised expectancy(2010) Suarez-Almazor Yes Yes Yes Yes Yes Yes Yeset al. (2010) a Risk of bias for blinding was assessed only for whether participants were intended to be blind to the type of acupuncture they received (real or placebo) andwhether outcome assessors were blind to the participants’ allocation. Blinding of acupuncturists regarding acupuncture treatment is not possible, nor is itpossible to blind participants regarding an expectancy manipulation; therefore, these were not included in the risk of bias assessment. b In Bertisch et al. ,even though only placebo acupuncture was delivered for the period of interest, they were told they may receive real or placebo acupuncture and are, therefore,considered as blind to treatment allocation.simpliﬁed their expectancy assessment via dichotomisation on experimentally-induced pain to manipulate expectanciesor trichotomisation and three studies [49, 51, 53, 55] had and to employ electro-acupuncture, meaning that the eﬀectsrelatively small sample sizes given their correlational nature of each cannot be disentangled on the basis of the available[50, 53, 55]. data. Further, the largest study on a clinical outcome, that assessed expectancies, and that involved manual acupunc-4. Discussion ture, did ﬁnd evidence of a signiﬁcant relationship between expectancy and acupuncture outcomes . It was also theGiven that patient expectancies are often proposed to be a case that some studies were at higher risk of bias than others.key factor in acupuncture’s eﬀectiveness compared with no The diﬀerences in study design and inconsistent resultstreatment or standard care [28, 29], relatively few studies across the identiﬁed studies raise important considerationshave examined the relationship between expectancies and regarding which methodological approach is best equippedtreatment responses following acupuncture. Our systematic to determine the contribution of patient expectancies tosearch identiﬁed only 14 unique studies testing the relation- acupuncture outcomes. The two most pertinent method-ship between patient expectancies and outcomes following ological issues are (1) whether to assess or manipulate ex-acupuncture needling, of which nine met our criteria for pectancies and (2) how to accurately assess expectancies.inclusion. The high level of heterogeneity across studies Of the nine studies identiﬁed here, ﬁve assessed expectan-and incomplete reporting in some meant that meta-analysis cies [49–51, 53, 55] and four manipulated expectancies [33,was not possible. A descriptive review revealed that while 48, 52, 54]. Studies that involve manipulating expectanciesthere was evidence of a signiﬁcant relationship between are better able to determine how patient expectancies con-patient expectancies and acupuncture needling outcomes in tribute to acupuncture outcomes because of their experi-some studies, others failed to ﬁnd these eﬀects. The pat- mental nature and might be considered superior for this rea-tern of results suggested that studies on experimentally- son. However, studies that only manipulate expectancies areinduced pain, that manipulated expectancies, or those in- entirely reliant on the ability of the manipulation to inﬂuencevolving electroacupuncture were more likely to ﬁnd a sig- expectancies. This leads to problems determining whetherniﬁcant relationship. However, caution is required in gen- an unsuccessful manipulation failed because it did not suf-eralising these results, as it was more common for studies ﬁciently inﬂuence expectancies or because the participants’
10 Evidence-Based Complementary and Alternative Medicineexpectancies had no eﬀect on their treatment response, as to the high heterogeneity in methodology and incompleteis the case in Berk et al.’s  study. Studies that assess reporting in some studies. While this does mean that we wereexpectancies have the advantage of being able to directly eval- unable to determine an average eﬀect size across studies, theuate the relationship between expectancy and acupuncture descriptive review provided here does highlight a numberoutcomes, thereby overcoming problems to do with relying of important methodological considerations that will informon the eﬃcacy of an expectancy manipulation. However, future research in this area. Secondly, as with most systematicthese types of studies might be considered a weaker source reviews, there is the possibility of publication bias. In theof evidence because they are correlational in nature. current case, this could mean that studies failing to ﬁnd a An apparently simple way to overcome this issue is to statistically signiﬁcant relationship between expectancy andinclude an assessment of expectancy in studies involving acupuncture outcomes were less likely to be published thanmanipulations. However, there are a number of other poten- those ﬁnding statistically signiﬁcant eﬀects, which may leadtial limitations associated with assessing expectancies that to overestimation of the inﬂuence of expectancy. We, there-need consideration. First, questioning participants about fore, encourage researchers conducting RCTs of acupuncturetheir expectancies regarding acupuncture’s eﬃcacy could to report, even brieﬂy, of any failures to ﬁnd a signiﬁcantundermine the study’s validity if it inﬂuences what they relationship between expectancy and acupuncture outcomes.expect or if it makes them question the purpose of the study. Finally, only papers published in English were reviewed,Second, determining the best time to assess expectancies is meaning that other relevant studies may be published inalso diﬃcult. Assessing them immediately before the ﬁrst other languages.acupuncture treatment provides a prospective assessment, In summary, there have been relatively few research stud-but expectancies may change during the course of the ies testing the relationship between expectancy and acupunc-treatment, especially if it lasts for more than a few days. ture outcomes. While there did appear to be evidence forOn the other hand, assessing expectancies immediately a signiﬁcant relationship between patient expectancies andbefore or immediately after the outcomes are assessed could treatment responses following acupuncture, there were somelead to priming that artiﬁcially inﬂates the strength of the inconsistencies across studies. Future studies attempting torelationship between expectancy and the outcome. Thirdly, address this question should, where possible, both manipu-there have been few systematic attempts to develop methods late and assess expectancies. However, considerations regard-of assessing expectancies, both within acupuncture research ing currently used methods of assessing expectancy, such asand in the placebo literature more broadly. Most of the timing and wording of the questions, need to be addressedstudies that assessed expectancies identiﬁed here used a ﬁrst in order to establish the best approach and to ensuresingle expectancy item. For the most part, these were 5-point the validity of these assessments and any conclusions drawnLikert-type scales, although, as can be seen in Table 1, both about the relationship between expectancy and acupuncturethe wording of the question and the labels for the response outcomes. Further, investigating potential moderators of theoptions varied considerably. It was also common for studies relationship between expectancy and acupuncture outcomes,assessing expectancies to dichotomise [49, 53, 55], or in such as type of acupuncture (real versus placebo), typeone case trichotomise , patients’ responses into diﬀerent of stimulation (manual versus electroacupuncture) wouldlevels of expectancy, however, categorising such variables has prove useful for better understanding the circumstancesbeen heavily criticised, because it can substantially reduce under which expectancies can inﬂuence treatment responsesstatistical power [57–59]. following acupuncture. Therefore, while studies that both manipulate and assessexpectancies are best able to test the relationship betweenexpectancy and acupuncture outcomes, questions regarding Acknowledgmentsthe inﬂuence of asking patients to report their expectancies We have no conﬂicts of interest in producing this review. Noand both when and how expectancies should be assessed funding was obtained for the review.need to be addressed empirically in order to determinethe most appropriate method of assessing expectancies. Ofcourse, it may not always be practical to incorporate an Referencesexpectancy manipulation into a trial of acupuncture, asthis may require substantially larger samples to achieve the  D. C. Cherkin, K. J. Sherman, A. L. Avins et al., “A randomizedsame level of power or may raise ethical considerations if trial comparing acupuncture, simulated acupuncture, anddeception is required. In these circumstances, it is still useful usual care for chronic low back pain,” Archives of Internalto assess expectancies as this can provide estimates of the Medicine, vol. 169, no. 9, pp. 858–866, 2009.relationship between expectancy and treatment responses  M. Haake, H. H. M¨ ller, C. 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