Indirect acquisition of pain-related fear: an experimental study of observational learning using coloured cold metal bars

Placebo Hypoalgesia and Nocebo Hyperalgesia Induced by Observational Learning May Be Difficult to Disentangle in a Laboratory Setting

Observational learning (OBL) (seeing pain/pain treatment in others) can evoke placebo hypoalgesia and nocebo hyperalgesia. Data that compare these effects and illuminates the role of expectations and empathy are scarce. Healthy participants (n = 105) were randomized to: 1) placebo OBL, 2) nocebo OBL, or 3) no-observation control group. OBL consisted of a model simulating pain relief or increase after a sham ointment was applied to one arm. Pain was evoked with thermal stimuli on both arms (ointment, contralateral) at baseline and postobservation. Expectations, pain ratings, and physiological data (eg, skin conductance level) were collected. A 3 × 2 × 2 (Group × Arm × Phase) mixed analyses of variance revealed a 3-way interaction that confirmed that OBL modulates pain: F(2, 93) = 6.08, P = .003, ηp2 = .12. Significant baseline-to-post-observation pain increases were shown in the nocebo OBL group, with a bigger increase for the arm with ointment (both P ≤ .007). In the placebo OBL group, pain was higher for the contralateral relative to the ointment arm (P < .001). Baseline-to-post-observation pain increase was significant for the contralateral arm (P < .001). Expectation mediated these effects. Skin conductance level decreased over time during ointment trials in the nocebo OBL group, suggesting reduced physiological arousal. The findings illustrate that OBL modulates pain through expectations. In the placebo OBL group, the pain did not decrease for the ointment but increased for the contralateral stimuli, which may reflect nocebo learning. Experimental OBL paradigms typically examine relative differences between ointment and contralateral cues. This can complicate disentangling placebo hypoalgesia and nocebo hyperalgesia in laboratory settings. Implications for existing theories are discussed. PERSPECTIVE: Data that systematically compare placebo hypoalgesia and nocebo hyperalgesia induced by OBL are scarce. The current work illustrates that these effects may be more difficult to disentangle than previously assumed, which could have implications for existing theories on OBL and placebo effects and their translation to clinical practice.

Learning pain from others: a systematic review and meta-analysis of studies on placebo hypoalgesia and nocebo hyperalgesia induced by observational learning

ABSTRACT

Observing someone experience pain relief or exacerbation after an intervention may induce placebo hypoalgesia or nocebo hyperalgesia. Understanding the factors that contribute to these effects could help in the development of strategies for optimizing treatment of chronic pain conditions. We systematically reviewed and meta-analyzed the literature on placebo hypoalgesia and nocebo hyperalgesia induced by observational learning (OL). A systematic literature search was conducted in the databases PubMed, PsycINFO, Web of Science, ScienceDirect, PsycARTICLES, Scopus, and Academic Search Ultimate. Twenty-one studies were included in the systematic review, 17 of which were suitable for meta-analysis (18 experiments; n = 764 healthy individuals). The primary end point was the standardized mean difference (SMD) for pain following placebo cues associated during OL with low vs high pain. Observational learning had a small-to-medium effect on pain ratings (SMD 0.44; 95% confidence interval [CI] 0.21-0.68; P < 0.01) and a large effect on pain expectancy (SMD 1.11; 95% CI 0.49-2.04; P < 0.01). The type of observation (in-person vs videotaped) modulated the magnitude of placebo hypoalgesia/nocebo hyperalgesia ( P < 0.01), whereas placebo type did not ( P = 0.23). Finally, OL was more effective when observers' empathic concern (but no other empathy-related factors) was higher ( r = 0.14; 95% CI 0.01-0.27; P = 0.03). Overall, the meta-analysis demonstrates that OL can shape placebo hypoalgesia and nocebo hyperalgesia. More research is needed to identify predictors of these effects and to study them in clinical populations. In the future, OL could be an important tool to help maximize placebo hypoalgesia in clinical settings.

The Effect of Observing High or Low Pain on the Development of Central Sensitization

It is unknown whether watching other people in high pain increases mechanical hypersensitivity induced by pain. We applied high-frequency electrical stimulation (HFS) on the skin of healthy volunteers to induce pinprick mechanical hypersensitivity. Before HFS participants were randomly allocated to 2 groups: in the low pain group, which was the control condition, they watched a model expressing and reporting lower pain scores, in the high pain group the model expressed and reported higher scores. The 2 videos were selected on the basis of a pilot/observational study that had been conducted before. We tested the differences in perceived intensity of the HFS procedure, in the development of hypersensitivity and the role of fear and empathy. The high pain group reported on average higher pain ratings during HFS. The perceived intensity of hypersensitivity, but not the unpleasantness or the length of the area was higher in the high pain group. Our results suggest that watching a person expressing more pain during HFS increases one's own pain ratings during HFS and may weakly facilitate the development of secondary mechanical hypersensitivity, although this latter result needs replication. PERSPECTIVE: Observing a person in high pain can influence the perceived pain intensity of a procedure leading to secondary mechanical hypersensitivity, and has a weak effect on hypersensitivity itself. The role of fear remains to be elucidated.

Action observation as a treatment option for fear avoidance behavior in chronic spinal pain

Psychological factors play an essential role in the maintenance of various chronic pain states, with fear avoidance beliefs contributing to significant functional limitation and disability in chronic spinal pain. Fear avoidance behaviors are typically managed with cognitive-behavioral interventions such as graded exposure to feared movements and graded activity programs. However, attempts to make patients with high pain-related fear perform painful actions using graded exposure therapy can be very challenging. These fear avoidance beliefs in individuals with pain are usually acquired through previous pain experiences, observation, and threating verbal input from others that movement is harmful to the spinal structures. Observational learning of fear has been recently demonstrated in several experimental studies, where participants acquired fear of pain after observing the distressed painful expressions of the volunteers performing a painful cold pressor task. The primary purpose of this paper is to propose action observation, a cognitive rehabilitation technique, as one of the treatment options for reducing fear avoidance behavior in chronic spinal pain. Action observation involves the visualization of others performing a movement or an action to influence motor behavior positively and is mainly used in stroke rehabilitation. The paper hypothesizes that the pain-related fear of movement may be reduced through observation of others performing threatening movements successfully without displaying pain or discomfort. Action observation of others successfully executing a strenuous task may break the preexisting cognitive association between movement and pain among patients with high pain-related fear. Other possible mechanisms through which observation may influence pain-related fear could be the activation of mirror neuron systems and subsequent modulation of nociceptive information through the interconnections between the amygdala (one of the brain centers for fear), descending pain modulatory system and higher cortical centers. Few initial studies that investigated the effects of action observation on other outcomes of pain, such as pain severity are described to review the hypothesis. Considering the influence of observational learning on pain-related fear, action observation may be explored as potential adjunctive treatment to reduce fear avoidance behavior in chronic spinal pain.

How Does Observational Learning Produce Placebo Effects? A Model Integrating Research Findings

There is a growing body of evidence proving that observational learning, in addition to classical conditioning and verbal suggestions, may induce both placebo analgesia and nocebo hyperalgesia. However, much less is known about the mechanisms and factors influencing placebo effects induced by observational learning. The paper critically reviews the research findings in the field in the context of Bandura’s social learning theory. We apply Bandura’s taxonomy of the sources of social learning (behavioral, symbolic, and verbal modeling) and discuss the results of previous studies. Critical points in the placebo effects induced by observational learning are identified. We discuss aspects of behavior presented by the model (both verbal and non-verbal) involved in the formation of placebo effects induced by observational learning as well as the role of expectancies in this process. As a result, we propose a model that integrates the existing research findings. The model shows the main ways of transmission of pain-related information from the model to the observer. It highlights the role of expectancies and the individual characteristics of the observer in formation of placebo analgesia and nocebo hyperalgesia induced by observational learning. Finally, we propose future research directions based on our model.

Activity Limitations in Patients with Axial Spondyloarthritis: A Role for Fear of Movement and (Re)injury Beliefs

Objective.

To determine whether fear of movement and (re)injury [FOM/(R)I] beliefs, measured with the Tampa Scale for Kinesiophobia 11-item version (TSK-11), influence activity limitations and mediate the relationship between pain severity and activity limitations in axial spondyloarthritis (axSpA).

Methods.

In 173 patients with axSpA, these data were collected: sex, body mass index, disease duration, medication, activity limitations (BASFI; Bath Ankylosing Spondylitis Functional Index), disease activity [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI); BASDAIinf, items 5 and 6; BASDAIpain, items 2 and 3; C-reactive protein and physician’s global assessment], spinal mobility (BASMI; Bath Ankylosing Spondylitis Metrology Index), and FOM/(R)I (TSK-11). Scaling assumptions and reliability of TSK-11 were tested with item-to-total correlations, item variances, and Cronbach’s alpha coefficient. Hypothesis testing determined TSK-11’s construct validity. Multiple linear regression showed the contribution of TSK-11 to BASFI (enter and backward modeling). Mediation by TSK-11 was analyzed (bias-corrected bootstrapping and Sobel test).

Results.

Adequate scale (Cronbach’s alpha = 0.80) and item internal consistency (range item-scale correlations 0.41–0.58, except for item 5, r = 0.23), equal item-scale correlations, and item variances were found for TSK-11. Construct validity was confirmed, except for the hypothesized positive relationship between TSK-11 and BASMI. Regression models (enter method, adjusted R2 range 53–74%) consistently identified TSK-11 as a determinant of BASFI (β range 0.155 to 0.321, p < 0.05), although BASMI (β range 0.441 to 0.537) and disease activity (β range 0.243 to 0.571, p < 0.05) were the largest determinants. TSK-11 partially mediated the BASDAIpain/BASFI relationship (B = 0.107; Sobel test, p = 0.004; bias-corrected CI 0.046–0.197).

Conclusion.

TSK-11 is a promising and valid tool to assess fearful beliefs in relation to activity limitations in axSpA. Future research applying TSK-11 may reveal FOM/(R)I as a novel treatment target in axSpA.

Assessment of social transmission of threats in humans using observational fear conditioning

Across the human life span, fear is often acquired indirectly by observation of the emotional expressions of others. The observational fear conditioning protocol was previously developed as a laboratory model for investigating socially acquired threat responses. This protocol serves as a suitable alternative to the widely used Pavlovian fear conditioning, in which threat responses are acquired through direct experiences. In the observational fear conditioning protocol, the participant (observer) watches a demonstrator being presented with a conditioned stimulus (CS) paired with an aversive unconditioned stimulus (US). The expression of threat learning is measured as the conditioned response (CR) expressed by the observer in the absence of the demonstrator. CRs are commonly measured as skin conductance responses, but behavioral and neural measures have also been implemented. The experimental procedure is suitable for divergent populations, can be administered by a graduate student and takes ∼40 min. Similar protocols are used in animals, emphasizing its value as a translational tool for studying socioemotional learning.

Towards a science and practice of resilience in the face of pain

The primary objective of this paper is to discuss how a resilience approach to (chronic) pain may advance our current understanding of (mal)adaptation to pain. Different resilience perspectives are described, and future challenges for research, prevention and treatment of (chronic) pain are discussed. Literature searches were performed in Web of Science and PubMed to identify relevant literature on risk and resilience in the context of pain. Resilience can be best defined as the ability to restore and sustain living a fulfilling life in the presence of pain. The Psychological Flexibility Model, the Broaden-and-Build Theory, and Self-Determination Theory are described as theories that may provide insight into resilience within the context of (chronic) pain. We describe how a resilience paradigm shifts the outcomes to pursue in pain research and intervention and argue the need for including positive outcomes in addition to negative outcomes. Psychological flexibility, positive affect and basic psychological needs satisfaction are described as potentially important resilience mechanisms with the potential to target both sustainability and recovery from pain. A resilience approach to chronic pain may have important implications for the prevention and treatment of chronic pain problems, as it may give specific indications on how to empower patients to continue living a fulfilling life (in the presence of pain).

SIGNIFICANCE

The resilience approach put forward in this review spotlights sustainability of positive outcomes (e.g. engagement in meaningful activities) in the presence of pain as an outcome to pursue beyond recovery of negative outcomes. We illuminate the evidence-base and practical application of promising resilience mechanisms (positive emotions, psychological flexibility, needs satisfaction). For this article, a commentary is available at the Wiley Online Library.