Placebo-like analgesia via response imagery

Conclusions Regarding the Role of Expectations in Placebo Analgesia Studies May Depend on How We Investigate It: A Meta-Analysis, Systematic Review, and Proposal for Methodological Discussions

OBJECTIVE

Expectations are highlighted as a key component in placebo effects. However, there are different approaches to whether and how placebo studies should account for expectations, and the direct contribution has yet to be estimated in meta-analyses. Using different methodological approaches, this meta-analysis and systematic review examines the extent to which expectations contribute to pain in placebo studies.

METHODS

The databases PubMed, PsycINFO, Embase, and Web of Science were searched for placebo analgesia mechanism studies with numerical measures of both expectations and pain. Thirty-one studies, comprising 34 independent study populations (1566 subjects: patients and healthy participants) were included. Two meta-analyses were conducted: meta-analysis 1, using study-level data, estimated the effect of expectation interventions without taking measures of expectations into account (expectations assumed); and meta-analysis 2, using individual-level data, estimated the direct impact of participants' expectations on pain (expectations assessed). Risk of bias was assessed using the Cochrane risk-of-bias tool.

RESULTS

Meta-analysis 1 showed a moderate effect of expectation interventions over no expectation intervention on pain intensity (Hedges g = 0.45, I2 = 54.19). Based on 10 studies providing individual-level data, meta-analysis 2 showed that expectations predicted pain intensity in placebo and control groups ( b = 0.36, SE = 0.05), although inconsistently across study methodologies.

CONCLUSIONS

Participants' expectations contributed moderately to pain in placebo analgesia studies. However, this may largely be influenced by how we measure expectations and how their contribution is conceptualized and analyzed-both within and across studies.

Imaginary pills and open-label placebos can reduce test anxiety by means of placebo mechanisms

Placebos have been shown to be beneficial for various conditions even if administered with full transparency. Hence, so-called open-label placebos (OLPs) offer a new way to harness placebo effects ethically. To take this concept one step further, this study aimed at evaluating placebo effects without the use of a physical placebo, i.e., by imagining taking a pill. Healthy students (N = 173) with self-reported test anxiety were either randomized to an imaginary pill (IP; n = 55), an OLP (n = 59) or a control group (CG; n = 59). Both intervention groups were instructed to take two pills daily for three weeks. Primary outcome was test anxiety, secondary outcomes were sleep quality, general well-being and test performance. Groups test anxiety differed at study-endpoint, F(2,169) = 11.50, p < .001. Test anxiety was lower in the intervention groups compared to the CG, t(169) = - 4.44, p < .001, d = - 0.71. The interventions did not differ significantly, i.e., both were similarly efficacious, t(169) = 0.61, p = .540, d = 0.11. The interaction between group and time in explaining test anxiety was significant, F(5,407.93) = 6.13, p < .001. OLPs and IPs reduced test anxiety in healthy participants compared to the CG. This finding opens the door for a novel and ethical method to harness placebo effects.

Effects of Self-Efficacy and Outcome Expectations on Motor Imagery-Induced Thermal and Mechanical Hypoalgesia: A Single-Blind Randomised Controlled Trial

The main aim of this study was to assess whether self-efficacy (SE) and outcome expectations (OEs) modulate the hypoalgesic effect induced by motor imagery (MI). A total of 75 asymptomatic participants were randomly assigned to the positive (SE+, OE+), negative (SE-, OE-) or non-expectation (CG) groups. Heat pain threshold (HPT) and pain pressure threshold (PPT) were the main variables. Cold detection threshold (CDT), warm detection threshold (WDT), heart rate (HR) and perceived fatigue were the secondary variables. The variables were assessed preintervention, immediately postintervention and 10 min postintervention, except for HR, which was measured continuously during the intervention. Regarding HPT, significant within-group pre-post differences were found in the OE+ group, with a low effect size (p = 0.01, d = -0.39). With regard to ΔPPT, significant intergroup differences were found in Δpost-pre between the SE+ and CG groups (p = 0.012, d = 1.04) and also between SE+ and OE- (p = 0.006, d = 1.08), both with a large effect size. CG, SE-, and OE- groups had poorer CDT and WDT. Regarding HR, significant intergroup differences were found in the postintervention measurement between OE+ and SE-, with a large effect size (p = 0.016, d = 1.34). Lastly, no between-group differences were found regarding perceived fatigue (p > 0.05). The results obtained showed that positive expectations have a slight influence on the increase in heat and mechanical pain detection thresholds. Positive and non-expectancy groups showed an autonomic activation. The results also showed that negative expectations led to poorer perceptual processes.

Hypoalgesic effects of a blood flow restriction technique at moderate intensity with or without motor imagery: a single-blind randomized controlled trial

PURPOSE

The main objective was to assess the hypoalgesic effect of adding blood flow restriction (BFR) training with or without motor imagery (MI) to moderate-intensity exercise. The secondary objective was to analyse the correlations of the pain pressure thresholds (PPTs) regarding perceived pain intensity, perceived fatigue, and cuff pressure discomfort.

METHODS

A sample of 42 asymptomatic participants were randomly assigned to 3 groups: control group (CG), BFR group, and BFR with MI group. All participants performed a squat exercise at an intensity of 60% of 1RM. For the BFR groups, blood occlusion occurred at 80% of maximal arterial occlusive pressure. Local, bilateral, and distal PPT were assessed pre-intervention, post-intervention and 48 h post-intervention. The perceived fatigue was assessed post-intervention, and pain intensity was assessed only 48 h post-intervention.

RESULTS

There were intragroup differences in the CG and BFR + MI group in the local PPT between the pre-intervention and post-intervention measurements (p = 0.039, d= -0.32 and p = 0.009, d= -0.46, respectively) and only in the CG in the bilateral PPT (p = 0.002, d= -0.41). The CG and BFR group showed significant differences at 48 h post-intervention, with a decrease in local PPT (p = 0.009, d = 0.51 and p = 0.049, d = 0.43, respectively) and bilateral PPT (p = 0.004, d = 0.53 and p = 0.021, d = 0.46, respectively). There was a negative moderate correlation between local PPT at the post-intervention time and perceived discomfort of the occlusion device only in the BFR group (r=-0.54, p = 0.045).

CONCLUSION

Moderate-intensity resistance training with high occlusion did not generate hypoalgesia but did appear to generate a hyperalgesic response within 48 h after the intervention.

Underpredicting pain: an experimental investigation into the benefits and risks

ABSTRACT

Expectancies can shape pain and other experiences. Generally, experiences change in the direction of what is expected (ie, assimilation effects), as seen with placebo effects. However, in case of large expectation-experience discrepancies, experiences might change away from what is expected (ie, contrast effects). Previous research has demonstrated contrast effects on various outcomes, but not pain. We investigated the effects of strong underpredictions of pain on experienced pain intensity. In addition, we assessed related outcomes including (certainty of) expectations, fear of pain, pain unpleasantness, autonomic responses, and trust. Healthy participants (study 1: n = 81 and study 2: n = 123) received verbal suggestions that subsequent heat stimuli would be moderately or highly painful (correct prediction), mildly painful (medium underprediction; study 2 only), or nonpainful (strong underprediction). Both studies showed that participants experienced less intense pain upon strong underprediction than upon correct prediction (ie, assimilation). Expected pain, fear of pain, and pain unpleasantness were generally also lowered. However, strong underprediction simultaneously lowered certainty of expectations and trust in the experimenter. Study 2 indicated that the effects of strong underprediction vs medium underprediction generally did not differ. Moreover, study 2 provided some indications for reduced heart rate and skin conductance levels but increased skin conductance responses upon strong underprediction. In conclusion, even strong underpredictions of pain can reduce pain (ie, cause assimilation), although not significantly more than medium underpredictions. However, strong underpredictions can cause uncertainty and undermine trust. These findings suggest that healthcare providers may wish to be cautious with providing overly positive information about painful medical procedures.

Effects of additional action observation to an exercise program in patients with chronic pain due to knee osteoarthritis: A randomized-controlled trial

BACKGROUND

Knee osteoarthritis (OA) leads to pain, stiffness, and functional impairment and eventually decreased level of the quality of life. Although several treatment methods have been used to achieve pain relief, patients still complain of pain.

OBJECTIVE

The aim of this study was to investigate the effects of the addition of action observation therapy to an exercise program on pain severity, pressure pain threshold, kinesiphobia functionality, and pain catastrophization in knee OA patients with chronic pain.

METHODS

This prospective, randomized-controlled, superiority trial included a total of 36 patients with knee OA. The patients were randomly divided into two groups as the treatment group (n = 18) receiving action observation therapy in addition to exercise and control group (n = 18) receiving exercise alone. The interventions were performed three times weekly for six weeks. The primary outcomes were pain and pressure pain threshold. Secondary outcomes were kinesiphobia, functionality, and pain catastrophization. All participants were assessed at baseline (pre-intervention) and after the six-week treatment (post-intervention).

RESULTS

There was no significant difference in the primary and secondary outcome measures before and after the intervention between the groups (p > 0.05). Both groups showed a significant improvement in all outcome measures after the intervention (p < 0.01).

CONCLUSION

Our study results suggest that action observation therapy in addition to an exercise program does not contribute any additional benefits to pain, pressure pain threshold, kinesiophobia, pain catastrophization, and functionality in knee OA patients with chronic pain. Nonetheless, further large-scale, long-term, prospective studies are needed to gain a better understanding on this subject.

'External timing' of placebo analgesia in an experimental model of sustained pain

BACKGROUND

Research on placebo analgesia commonly focuses on the impact of information about direction (i.e., increase or decrease of pain) and magnitude of the expected analgesic effect, whereas temporal aspects of expectations have received little attention so far. In a recent study, using short-lasting, low-intensity stimuli, we demonstrated that placebo analgesia onset is influenced by temporal information. Here, we investigate whether the same effect of temporal suggestions can be found in longer lasting, high-intensity pain in a Cold Pressor Test (CPT).

METHODS

Fifty-three healthy volunteers were allocated to one of three groups. Participants were informed that the application of an (inert-)cream would reduce pain after 5 min (P5) or 30 min (P30). The third group was informed that the cream only had hydrating properties (NE). All participants completed the CPT at baseline and 10 (Test 10) and 35 min (Test 35) following cream application. Percentage change in exposure time (pain tolerance) from baseline to Test 10 (Δ10) and to Test 35 (Δ35) and changes in heart rate (HR) during CPT were compared between the three groups.

RESULTS

Δ10 was greater in P5 than in NE and P30, indicating that analgesia was only present in the group that was expecting an early onset of analgesia. Δ35 was greater in P5 and P30 compared to NE, reflecting a delayed onset of analgesia in P30 and maintained analgesia in P5. HR differences between groups were not significant.

CONCLUSIONS

Our data suggest that 'externally timing' of placebo analgesia may be possible for prolonged types of pain.

SIGNIFICANCE

Research on placebo effects mainly focuses on the influence of information about direction (i.e., increase or decrease of pain) and magnitude (i.e., strong or weak) of the expected effect but ignores temporal aspects of expectations. In our study in healthy volunteers, the reported onset of placebo analgesia followed the temporal information provided. Such 'external timing' effects could not only aid the clinical use of placebo treatment (e.g., in open-label placebos) but also support the efficacy of active drugs.

Imagined and Actual Acupuncture Effects on Chronic Low Back Pain: A Preliminary Study

Background

Research suggests that imagined experiences can produce brain responses similar to those produced by actual experiences. Shared brain responses that support both imagination and perception may underlie the functional nature of mental imagery. In a previous study, we combined acupuncture and imagery to develop a new treatment method, video-guided acupuncture imagery treatment (VGAIT). We found that VGAIT significantly increased pain thresholds in healthy subjects. The aim of this study is to extend our previous finding by investigating whether VGAIT can relieve symptoms in patients with chronic low back pain.

Methods

We first performed a single-arm study in which we administered video-guided acupuncture imagery treatment (VGAIT) on patients with chronic low back pain (cLBP) (Study 1, n = 18, 12 females). We then compared our findings to those from a recently published study in which real or sham acupuncture treatment was applied on patients with cLBP (Study 2, n = 50, 31 females) using a similar protocol. All patients in Studies 1 and 2 received 6 treatments over 4 weeks.

Results

All three treatments (VGAIT, real, and sham acupuncture) significantly reduced pain severity as measured by a low back pain bothersomeness score. VGAIT produced similar effects to real acupuncture (p = 0.97) and nonsignificantly greater pain bothersomeness relief compared to sham acupuncture (p = 0.14). Additional analysis showed that there was no significant difference on the sensations evoked by different treatment modalities.

Conclusion

These findings support VGAIT as a promising method for pain management.

Motor Imagery and Action Observation of Specific Neck Therapeutic Exercises Induced Hypoalgesia in Patients with Chronic Neck Pain: A Randomized Single-Blind Placebo Trial

The aim of the present study was to explore the pain modulation effects of motor imagery (MI) and action observation (AO) of specific neck therapeutic exercises both locally, in the cervical region, and remotely. A single-blind, placebo clinical trial was designed. A total of 30 patients with chronic neck pain (CNP) were randomly assigned to an AO group, MI group, or placebo observation (PO) group. Pain pressure thresholds (PPTs) of C2/C3, trapezius muscles, and epicondyle were the main outcome variables. Secondary outcomes included heart rate measurement. Statistically significant differences were observed in PPTs of the cervical region in the AO and MI groups between the preintervention and first postintervention assessment. Significant differences were found in the AO group in the epicondyle between the preintervention, first and second post-intervention assessments. Regarding heart rate response, differences were found in the AO and MI groups between the preintervention and average intervention measurements. AO and MI induce immediate pain modulation in the cervical region and AO also induces remote hypoalgesia. OA appears to lead to greater pain modulation as well as a greater heart rate response, however, both should be clinically considered in patients with CNP.

The impact of valence framing on response expectancies of side effects and subsequent experiences: a randomised controlled trial

Objective: Pre-treatment side effect expectancies often influence subsequent experiences; however, expectancy-based reduction strategies are lacking. We explored whether framing information about adverse responses (in positive or negative formats) altered expectancies and experiences of a cold pressor task. We further investigated associations between expectancies and experiences, to inform potential interventions. Design: Healthy volunteers (N = 134), randomised to receive positively- or negatively-framed pre-cold pressor task information, self-rated 12 expectancies for cold pressor experiences, emotional state and coping style. Main Outcome Measures: Self-reports of the same 12-experiences (recorded during and after the experiment) were assessed. Results: Framing had minimal impact on expectancies and experiences; however, discomfort threshold (p = .08, d = 0.22) showed a trend in the expected direction. Hierarchical regressions revealed expectancies uniquely, significantly predicted 6-23% of the variance for 11 subsequent experiences. Following a popular charity event (Ice Bucket Challenge), all participants showed higher 'discomfort thresholds' (p = .001, d = 0.59), and those in the negative frame reported more overall 'discomfort' (p = .01, d = 0.60) than participants in the positive condition. Conclusion: Expectancies uniquely influenced subsequent cold pressor experiences. Framing had minimal impact in this 'analogue' medical setting, only influencing 'discomfort threshold'. 'Discomfort threshold' and overall 'discomfort' were also impacted by a social media challenge, highlighting a potential area for intervention.

The effects of a gamified approach avoidance training and verbal suggestions on food outcomes

There is initial support for the effectiveness of approach-avoidance trainings in altering food-related health behaviors. Furthermore, outcome expectancies induced by verbal suggestions might optimize the effectiveness of these interventions, as shown in placebo research. The present study investigated the effectiveness of a gamified approach-avoidance training on food-related outcomes and whether verbal suggestions could strengthen those effects. A total of 120 participants were randomly assigned to 1 of 4 conditions: serious gaming only, verbal suggestions only, serious gaming combined with verbal suggestions, or a gaming control condition. Virtual food preference and food choice were assessed with a food choice task, with pairs differing in healthiness or in healthiness and attractiveness. Implicit food preference was assessed with an Implicit Association Test and food intake with a bogus taste test. Participants in both serious gaming conditions made healthier food choices for pairs differing in healthiness and attractiveness and had healthier implicit food preferences compared to gaming control. No effects were found on food intake. These findings provide the first preliminary support for the effects of a gamified approach-avoidance training on virtual food choice and implicit food preference. Future studies should further elucidate these effects, also in other health domains such as physical activity.

[Placebo and nocebo effects on itch : Methodological and clinical implications]

Patients often experience positive (placebo) or negative (nocebo) treatment effects due to the positive or negative expectations they have about the treatment. Placebo and nocebo effects have only relatively recently received attention for itch. Experimental studies indicate that, in line with research in other areas, such as pain, learning via verbal suggestion and conditioning plays a key role in placebo and nocebo effects on itch. Results on contagious itch emphasize the role of observational learning and suggest that itch sensations might be particularly susceptible to suggestion and therefore placebo and nocebo effects. Substantial itch reductions in the placebo arms of clinical trials suggest that placebo effects are also important for clinical practice. In this article, an overview is given of how placebo and nocebo effects on itch can optimally be used in research and for the treatment of itch.