The Signaling Theory of Symptoms : An Evolutionary Explanation of the Placebo Effect

The double invisibility of Long Covid in children

The Covid-19 pandemic has been dominated by discussions of mild and short-lasting cases or acutely serious or lethal forms of the disease; less attention has been paid to long-term Covid-19 symptoms ('Long Covid'), particularly in children. This analysis of the experiences of children and adolescents with Long Covid, and those of their parents/caregivers, argues that children with Long Covid encounter a 'double invisibility' due to the condition's limited social currency and their status as the youngest members of society. We draw on 39 narrative interviews about children's and adolescents' experiences, conducted in 2021-2022 in the United Kingdom. The occurrence of Long Covid in children challenges key aspects of a dominant pandemic narrative, some of which have persisted from the early stages of the pandemic into 2023. Analysis of our qualitative interviews demonstrates that participant experiences were shaped and undermined by the convergence of three elements of the dominant pandemic narrative: that Covid-19 is mild, and everyone recovers; that children are not badly affected by Covid-19; and that worst of the pandemic was essentially 'over' as early as 2021/2022. In the face of these characterisations of Covid-19 experience, young people and their families reported significant additional challenges in making the illness experiences of children and adolescents visible, and thus in gaining appropriate support from medical and educational professionals. We interpret this in relation to 'social currency' - the extent to which an illness elicits understanding and acceptance by wider society. Children and adolescents with Long Covid struggled to signal the severity of their condition and elicit care in the manner expected for other debilitating illnesses. This was exacerbated by assumptions and stereotypes about unwell children and adolescents, and their parents, and questioning of their candidacy as reliable, trustworthy patients.

Pain: Behavioural expression and response in an evolutionary framework

An evolutionary perspective offers insights into the major public health problem of chronic (persistent) pain; behaviours associated with it perpetuate both pain and disability. Pain is motivating, and pain-related behaviours promote recovery by immediate active or passive defence; subsequent protection of wounds; suppression of competing responses; energy conservation; vigilance to threat; and learned avoidance of associated cues. When these persist beyond healing, as in chronic pain, they are disabling. In mammals, facial and bodily expression of pain is visible and identifiable by others, while social context, including conspecifics' responses, modulate pain. Studies of responses to pain emphasize onlooker empathy, but people with chronic pain report feeling disbelieved and stigmatized. Observers frequently discount others' pain, best understood in terms of cheater detection-alertness to free riders that underpins the capacity for prosocial behaviours. These dynamics occur both in everyday life and in clinical encounters, providing an account of the adaptiveness of pain-related behaviours.

Brain-to-brain mechanisms underlying pain empathy and social modulation of pain in the patient-clinician interaction

Social interactions such as the patient-clinician encounter can influence pain, but the underlying dynamic interbrain processes are unclear. Here, we investigated the dynamic brain processes supporting social modulation of pain by assessing simultaneous brain activity (fMRI hyperscanning) from chronic pain patients and clinicians during video-based live interaction. Patients received painful and nonpainful pressure stimuli either with a supportive clinician present (Dyadic) or in isolation (Solo). In half of the dyads, clinicians performed a clinical consultation and intake with the patient prior to hyperscanning (Clinical Interaction), which increased self-reported therapeutic alliance. For the other half, patient-clinician hyperscanning was completed without prior clinical interaction (No Interaction). Patients reported lower pain intensity in the Dyadic, relative to the Solo, condition. In Clinical Interaction dyads relative to No Interaction, patients evaluated their clinicians as better able to understand their pain, and clinicians were more accurate when estimating patients' pain levels. In Clinical Interaction dyads, compared to No Interaction, patients showed stronger activation of the dorsolateral and ventrolateral prefrontal cortex (dlPFC and vlPFC) and primary (S1) and secondary (S2) somatosensory areas (Dyadic-Solo contrast), and clinicians showed increased dynamic dlPFC concordance with patients' S2 activity during pain. Furthermore, the strength of S2-dlPFC concordance was positively correlated with self-reported therapeutic alliance. These findings support that empathy and supportive care can reduce pain intensity and shed light on the brain processes underpinning social modulation of pain in patient-clinician interactions. Our findings further suggest that clinicians' dlPFC concordance with patients' somatosensory processing during pain can be boosted by increasing therapeutic alliance.

The suffering ape hypothesis

The "fearful ape hypothesis" could be regarded as one aspect of a more general "suffering ape hypothesis": Humans are more likely to experience negative emotions (e.g., fear, sadness), aversive symptoms (e.g., pain, fever), and to engage in self-harming behavior (e.g., cutting, suicide attempts) because these might motivate affiliative, consolatory, and supportive behavior from their prosocial environment thereby enhancing evolutionary fitness.

Should I trust you? Investigating trustworthiness judgements of painful facial expressions

Past research indicates that patients' reports of pain are often met with skepticism and that observers tend to underestimate patients' pain. The mechanisms behind these biases are not yet fully understood. One relevant domain of inquiry is the interaction between the emotional valence of a stranger's expression and the onlooker's trustworthiness judgment. The emotion overgeneralization hypothesis posits that when facial cues of valence are clear, individuals displaying negative expressions (e.g., disgust) are perceived as less trustworthy than those showing positive facial expressions (e.g., happiness). Accordingly, we hypothesized that facial expressions of pain (like disgust) would be judged more untrustworthy than facial expressions of happiness. In two separate studies, we measured trustworthiness judgments of four different facial expressions (i.e., neutral, happiness, pain, and disgust), displayed by both computer-generated and real faces, via both explicit self-reported ratings (Study 1) and implicit motor trajectories in a trustworthiness categorization task (Study 2). Ratings and categorization findings partly support our hypotheses. Our results reveal for the first time that when judging strangers' facial expressions, both negative expressions were perceived as more untrustworthy than happy expressions. They also indicate that facial expressions of pain are perceived as untrustworthy as disgust expressions, at least for computer-generated faces. These findings are relevant to the clinical setting because they highlight how overgeneralization of emotional facial expressions may subtend an early perceptual bias exerted by the patient's emotional facial cues onto the clinician's cognitive appraisal process.

How reported outbreak data can shape individual behavior in a social world

Agencies reporting on disease outbreaks face many choices about what to report and the scale of its dissemination. Reporting impacts an epidemic by influencing individual decisions directly, and the social network in which they are made. We simulated a dynamic multiplex network model-with coupled infection and communication layers-to examine behavioral impacts from the nature and scale of epidemiological information reporting. We explored how adherence to protective behaviors (social distancing) can be facilitated through epidemiological reporting, social construction of perceived risk, and local monitoring of direct connections, but eroded via social reassurance. We varied reported information (total active cases, daily new cases, hospitalizations, hospital capacity exceeded, or deaths) at one of two scales (population level or community level). Total active and new case reporting at the population level were the most effective approaches, relative to the other reporting approaches. Case reporting, which synergizes with test-trace-and-isolate and vaccination policies, should remain a priority throughout an epidemic.

The evolution of the human healthcare system and implications for understanding our responses to COVID-19

The COVID-19 pandemic has revealed an urgent need for a comprehensive, multidisciplinary understanding of how healthcare systems respond successfully to infectious pathogens-and how they fail. This study contributes a novel perspective that focuses on the selective pressures that shape healthcare systems over evolutionary time. We use a comparative approach to trace the evolution of care-giving and disease control behaviours across species and then map their integration into the contemporary human healthcare system. Self-care and pro-health environmental modification are ubiquitous across animals, while derived behaviours like care for kin, for strangers, and group-level organizational responses have evolved via different selection pressures. We then apply this framework to our behavioural responses to COVID-19 and demonstrate that three types of conflicts are occurring: (1) conflicting selection pressures on individuals, (2) evolutionary mismatches between the context in which our healthcare behaviours evolved and our globalized world of today and (3) evolutionary displacements in which older forms of care are currently dispensed through more derived forms. We discuss the significance of understanding how healthcare systems evolve and change for thinking about the role of healthcare systems in society during and after the time of COVID-19-and for us as a species as we continue to face selection from infectious diseases.

Healing in a Social Context: The Importance of Clinician and Patient Relationship

When a patient presents to a health provider, the course of the disorder is composed of three effects: natural effects, specific effects, and contextual effects. Part of the contextual effect is due to the relationship between the healer and the patient. Social healing appears to be present in eusocial species and particularly well-developed in humans. Evidence for the importance of the relationship in healing is found in placebo studies, including placebo analgesics, medicine, and psychotherapy. Although the theory for how the relationship is therapeutic is not well-developed, four possible mechanisms are discussed. The implications for health care and the treatment of pain are discussed.

Dynamic brain-to-brain concordance and behavioral mirroring as a mechanism of the patient-clinician interaction

The patient-clinician interaction can powerfully shape treatment outcomes such as pain but is often considered an intangible "art of medicine" and has largely eluded scientific inquiry. Although brain correlates of social processes such as empathy and theory of mind have been studied using single-subject designs, specific behavioral and neural mechanisms underpinning the patient-clinician interaction are unknown. Using a two-person interactive design, we simultaneously recorded functional magnetic resonance imaging (hyperscanning) in patient-clinician dyads, who interacted via live video, while clinicians treated evoked pain in patients with chronic pain. Our results show that patient analgesia is mediated by patient-clinician nonverbal behavioral mirroring and brain-to-brain concordance in circuitry implicated in theory of mind and social mirroring. Dyad-based analyses showed extensive dynamic coupling of these brain nodes with the partners' brain activity, yet only in dyads with pre-established clinical rapport. These findings introduce a putatively key brain-behavioral mechanism for therapeutic alliance and psychosocial analgesia.

Emerging infectious disease and the challenges of social distancing in human and non-human animals

The 'social distancing' that occurred in response to the COVID-19 pandemic in humans provides a powerful illustration of the intimate relationship between infectious disease and social behaviour in animals. Indeed, directly transmitted pathogens have long been considered a major cost of group living in humans and other social animals, as well as a driver of the evolution of group size and social behaviour. As the risk and frequency of emerging infectious diseases rise, the ability of social taxa to respond appropriately to changing infectious disease pressures could mean the difference between persistence and extinction. Here, we examine changes in the social behaviour of humans and wildlife in response to infectious diseases and compare these responses to theoretical expectations. We consider constraints on altering social behaviour in the face of emerging diseases, including the lack of behavioural plasticity, environmental limitations and conflicting pressures from the many benefits of group living. We also explore the ways that social animals can minimize the costs of disease-induced changes to sociality and the unique advantages that humans may have in maintaining the benefits of sociality despite social distancing.

A reformulated contextual model of psychotherapy for treating anxiety and depression

This paper describes a reformulated contextual model that uses cognitive theory (dual process theory), motivation theory (personality) and behavioral adaptation (self-correcting control systems) to show how anxiety and depression are caused, treated and prevented by an interaction between people and contexts. Depression and anxiety are the result of implicit beliefs (not cognitions) that all experience is unrewarding and threatening, these being components of the implicit belief that life is bad. Implicit beliefs are formed automatically from contextual cues and in healthy individuals are consistent with rational appraisal. They become more negative than reality through a process of adaptation when behaviors, directed by rational thinking, repeatedly create cues that signify lack of reward or threat. Such behaviors occur when social or other obligations lead people to choose behaviors that fail to satisfy their own unique goals in life and approach threatening situations, contrary to their automatic reactions. Therapeutic interventions and lifestyle change reverse these adaptive processes by positive experiences that create positive implicit beliefs, a change effected in different ways by contextual and specific mechanisms both of which correct the same fault of negative implicit beliefs. Effective therapeutic relationships and interventions are achieved by detecting and responding to a patient's unique needs and goals and their associated implicit beliefs. Mental health requires not only that people experience life as good as defined by their own goals and beliefs but also the avoidance of contexts where social and other pressures induce people to behave in ways inconsistent with their automatically generated feelings.

Why Care: Complex Evolutionary History of Human Healthcare Networks

One of the striking features of human social complexity is that we provide care to sick and contagious individuals, rather than avoiding them. Care-giving is a powerful strategy of disease control in human populations today; however, we are not the only species which provides care for the sick. Widespread reports occurring in distantly related species like cetaceans and insects suggest that the building blocks of care for the sick are older than the human lineage itself. This raises the question of what evolutionary processes drive the evolution of such care in animals, including humans. I synthesize data from the literature to evaluate the diversity of care-giving behaviors and conclude that across the animal kingdom there appear to be two distinct types of care-behaviors, both with separate evolutionary histories: (1) social care behaviors benefitting a sick individual by promoting healing and recovery and (2) community health behaviors that control pathogens in the environment and reduce transmission within the population. By synthesizing literature from psychology, anthropology, and biology, I develop a novel hypothesis (Hominin Pathogen Control Hypothesis) to explain how these two distinct sets of behaviors evolved independently then merged in the human lineage. The hypothesis suggests that social care evolved in association with offspring care systems whereas community health behaviors evolved as a type of niche construction. These two types of behaviors merged in humans to produce complex, multi-level healthcare networks in humans. Moreover, each type of care increases selection for the other, generating feedback loops that selected for increasing healthcare behaviors over time. Interestingly, domestication processes may have contributed to both social care and community health aspects of this process.

The Contribution of Sociocultural Factors in Shaping Self-Reported Sickness Behavior

Sickness behavior is an evolutionarily conserved phenomenon found across a diverse range of animals involving a change in motivational priorities to theoretically maximize energetic investment in immune function and recovery. Typical components of sickness behavior include reduced sociability and activity, changes in diet, and depressed affect. Importantly, however, sickness behavior appears to be subject to other demands of life history in animal models, including reproduction and offspring survival. Thus, "feeling sick" is often context dependent with possible effects on morbidity and mortality. While humans may not always face the same life history trade-offs, sociocultural norms and values may similarly shape sickness behavior by establishing internalized parameters for "socially appropriate sickness." We explore the role of these factors in shaping sickness behavior by surveying a national U.S. sample (n = 1,259). Self-reported and recalled sickness behavior was measured using the SicknessQ instrument, which has previously been validated against experimentally induced sickness behavior. After post-stratification weighting and correction for Type I error, generalized linear models showed that sickness behavior is significantly affected by various factors across sex and racial/ethnic groupings. Income below the national mean (b = 1.85, adj. p = 0.025), stoic endurance of pain and discomfort (b = 1.61, adj. p < 0.001), and depressive symptomology (b = 0.53, adj. p < 0.001) were each associated with greater sickness behavior scores. Familism (b = 1.59, adj. p = 0.008) was positively associated with sickness behavior in men, but not women. Endurance of pain and discomfort was associated with greater sickness behavior in Whites only (b = 1.94, adj. p = 0.002), while familism approached significance in African Americans only (b = 1.86, adj. p = 0.057). These findings may reflect different social contexts of sickness across demographic groups, which may in turn have important implications for pathogen transmission and recovery times, potentially contributing to health disparities.

Persistence of pain in humans and other mammals

Evolutionary models of chronic pain are relatively undeveloped, but mainly concern dysregulation of an efficient acute defence, or false alarm. Here, a third possibility, mismatch with the modern environment, is examined. In ancestral human and free-living animal environments, survival needs urge a return to activity during recovery, despite pain, but modern environments allow humans and domesticated animals prolonged inactivity after injury. This review uses the research literature to compare humans and other mammals, who share pain neurophysiology, on risk factors for pain persistence, behaviours associated with pain, and responses of conspecifics to behaviours. The mammal populations studied are mainly laboratory rodents in pain research, and farm and companion animals in veterinary research, with observations of captive and free-living primates. Beyond farm animals and rodent models, there is virtually no evidence of chronic pain in other mammals. Since evidence is sparse, it is hard to conclude that it does not occur, but its apparent absence is compatible with the mismatch hypothesis. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

The placebo and its effects: A psychoneuroendocrinological perspective

Placebos are usually employed deceptively in clinical trials in order to control for non-specific effects. However, since placebos themselves have been found to cause clinically relevant changes and in some cases are indistinguishable from the verum they are tested against, this theoretically inert, but practically effective intervention has become a scientific discipline in its own right. In this review, it is argued that placebos are generic and genuine biopsychosocial interventions and as such are highly interesting candidates for a psychoneuroendocrinological perspective. Yet, despite a considerable conceptual proximity between explanatory models of placebos and their effects with psychoneuroendocrine models and findings, placebos have thus far not been subject to systematic psychoneuroendocrine examination. Consequently, it would be highly interesting and informative to make placebos the target of psychoneuroendocrine scrutiny.

Aversive medical treatments signal a need for support: a mathematical model

Ineffective, aversive and harmful medical treatments are common cross-culturally, historically and today. Using evolutionary game theory, we develop the following model to explain their persistence. Humans are often incapacitated by illness and injury, and are unusually dependent on care from others during convalescence. However, such caregiving is vulnerable to exploitation via illness deception, whereby people feign or exaggerate illness in order to gain access to care. Our model demonstrates that aversive treatments can counter-intuitively increase the range of conditions where caregiving is evolutionarily viable, because only individuals who stand to gain substantially from care will accept the treatment. Thus, contemporary and historical "ineffective" treatments may be solutions to the problem of allocating care to people whose true need is difficult to discern.

Therapeutic encounters and the elicitation of community care

Singh's analysis of shamanism is regarded as a contribution to the evolutionary study of healing encounters and evolutionary medicine. Shamans must create convincing healing spectacles, while sick individuals must convincingly express symptoms and suffering to motivate community care. Both have a shared interest in convincing onlookers. This is not restricted to shamanic treatment, but is still true in modern medical care.

Processing of Emotion in Functional Neurological Disorder

Emotions have traditionally been considered crucial in the development of functional neurological disorder, but the evidence underpinning this association is not clear. We aimed to summarize evidence for association between functional neurological disorder and emotions as formulated by Breuer and Freud in their conception of hysterical conversion. Based on a systematic literature search, we identified 34 controlled studies and categorized them into four groups: (i) autonomic arousal, (ii) emotion-motion interactions, (iii) social modulation of symptoms, and (iv) bodily awareness in FND. We found evidence for autonomic dysregulation in FND; convergent neuroimaging findings implicate abnormal limbic-motor interactions in response to emotional stimuli in FND. Our results do not provide enough empirical evidence for social modulation of the symptoms, but there is a clinical support for the role of suggestion and placebo in FND. Our results provide evidence for abnormal bodily awareness in FND. Based on these findings, we propose that functional neurological symptoms are forms of emotional reactions shaped into symptoms by previous experience with illness and possibly reinforced by actual social contexts. Additional research should investigate the effect of social context on the intensity of functional neurological symptoms and associated brain regions.

The Therapeutic Value of the Relationship for Placebo Effects and Other Healing Practices

Response to placebos has been documented experimentally for many medical disorders and had been verified in laboratory studies. However, the mechanisms that produce the response to placebos are not well identified, although it appears that the relationship between the medical practitioner and the patient plays an important role. Humans and other eusocial animals evolved to heal in a social context, so it is not surprising that the healing relationship is an important factor in the delivery of health services. Several well-designed studies have examined aspects of the relationship and response to placebo and the evidence is strong that various aspects of the relationship augment response to placebo. There is also meta-analytic evidence that the relationship improves physical and mental health services. Finally, there are three possible ways the relationship augments the response to placebo: combats loneliness, increases expectancies for relief, and coregulates emotions and decreases arousal.

Health Education and Symptom Flare Management Using a Video-based m-Health System for Caring Women With IC/BPS

OBJECTIVE

To assess effectiveness of the video-based m-health system providing videos dictated by physicians for health education and symptom self-management for patients with Interstitial cystitis/bladder pain syndrome (IC/BPS).

METHODS

An m-health system was designed to provide videos for weekly health education and symptom flare self-management. O'Leary-Sant index and visual analogue scale as well as SF-36 health survey were administrated to evaluate the disease severity and quality of life (QoL), respectively. A total of 60 IC/BPS patients were recruited and randomly assigned to either control group (30 patients) or study group (30 patients) in sequence depending on their orders to visit our urological clinic. Patients in both control and study groups received regular treatments, while those in the study group received additional video-based intervention. Statistical analyses were conducted to compare the outcomes between baseline and postintervention for both groups. The outcomes of video-based intervention were also compared with the text-based intervention conducted in our previous study.

RESULTS

After video-based intervention, patients in the study group exhibited significant effect manifested in all disease severity and QoL assessments except the pain visual analogue scale, while no significance was found in the control group. Moreover, the study group exhibited more significant net improvements than the control group in 7 SF-36 constructs, except the mental health. The limitations include short intervention duration (8 weeks) and different study periods between text-based and video-based interventions.

CONCLUSION

Video-based intervention is effective in improving the QoL of IC/BPS patients and outperforms the text-based intervention even in a short period of intervention.

Adaptive and non-adaptive models of depression: A comparison using register data on antidepressant medication during divorce

Divorce is associated with an increased probability of a depressive episode, but the causation of events remains unclear. Adaptive models of depression propose that depression is a social strategy in part, whereas non-adaptive models tend to propose a diathesis-stress mechanism. We compare an adaptive evolutionary model of depression to three alternative non-adaptive models with respect to their ability to explain the temporal pattern of depression around the time of divorce. Register-based data (304,112 individuals drawn from a random sample of 11% of Finnish people) on antidepressant purchases is used as a proxy for depression. This proxy affords an unprecedented temporal resolution (a 3-monthly prevalence estimates over 10 years) without any bias from non-compliance, and it can be linked with underlying episodes via a statistical model. The evolutionary-adaptation model (all time periods with risk of divorce are depressogenic) was the best quantitative description of the data. The non-adaptive stress-relief model (period before divorce is depressogenic and period afterwards is not) provided the second best quantitative description of the data. The peak-stress model (periods before and after divorce can be depressogenic) fit the data less well, and the stress-induction model (period following divorce is depressogenic and the preceding period is not) did not fit the data at all. The evolutionary model was the most detailed mechanistic description of the divorce-depression link among the models, and the best fit in terms of predicted curvature; thus, it offers most rigorous hypotheses for further study. The stress-relief model also fit very well and was the best model in a sensitivity analysis, encouraging development of more mechanistic models for that hypothesis.

An Evolutionary-Based Framework for Analyzing Mold and Dampness-Associated Symptoms in DMHS

Among potential environmental harmful factors, fungi deserve special consideration. Their intrinsic ability to actively germinate or infect host tissues might determine a prominent trigger in host defense mechanisms. With the appearance of fungi in evolutionary history, other organisms had to evolve strategies to recognize and cope with them. Existing controversies around dampness and mold hypersensitivity syndrome (DMHS) can be due to the great variability of clinical symptoms but also of possible eliciting factors associated with mold and dampness. An hypothesis is presented, where an evolutionary analysis of the different response patterns seen in DMHS is able to explain the existing variability of disease patterns. Classical interpretation of immune responses and symptoms are addressed within the field of pathophysiology. The presented evolutionary analysis seeks for the ultimate causes of the vast array of symptoms in DMHS. Symptoms can be interpreted as induced by direct (toxic) actions of spores, mycotoxins, or other fungal metabolites, or on the other side by the host-initiated response, which aims to counterbalance and fight off potentially deleterious effects or fungal infection. Further, individual susceptibility of immune reactions can confer an exaggerated response, and magnified symptoms are then explained in terms of immunopathology. IgE-mediated allergy fits well in this scenario, where individuals with an atopic predisposition suffer from an exaggerated response to mold exposure, but studies addressing why such responses have evolved and if they could be advantageous are scarce. Human history is plenty of plagues and diseases connected with mold exposure, which could explain vulnerability to mold allergy. Likewise, multiorgan symptoms in DMHS are analyzed for its possible adaptive role not only in the defense of an active infection, but also as evolved mechanisms for avoidance of potentially harmful environments in an evolutionary past or present setting.