Habituation to pain : a motivational-ethological perspective

Habituation to pain is mainly studied using external pain stimuli in healthy volunteers, often to identify the underlying brain mechanisms, or to investigate problems in habituation in specific forms of pain (eg, migraine). Although these studies provide insight, they do not address one pertinent question: Why do we habituate to pain? Pain is a warning signal that urges us to react. Habituation to pain may thus be dysfunctional: It could make us unresponsive in situations where sensitivity and swift response to bodily damage are essential. Early theories of habituation were well aware of this argument. Sokolov argued that responding to pain should not decrease, but rather increase with repeated exposure, a phenomenon he called “sensitization.” His position makes intuitive sense: Why would individuals respond less to pain that inherently signals bodily harm? In this topical review, we address this question from a motivational ethological perspective. First, we describe some core characteristics of habituation. Second, we discuss theories that explain how and when habituation occurs. Third, we introduce a motivational-ethological perspective on habituation and explain why habituation occurs. Finally, we discuss how a focus on habituation to pain introduces important methodological, theoretical, and clinical implications, otherwise overlooked

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

Literature reviews are not all the same

I was very interested in the discussion in the Editorial of the first 2017 issue of Torture Journal which referred to two similar literature reviews with opposite conclusions (Weiss et al., 2016; Patel, Williams, & Kellezi, 2016; Patel, Kellezi, & Williams, 2014) and would like to clarify and elaborate some of the differences, which I think are of relevance to the conclusions

A thematic synthesis of qualitative studies and surveys of the psychological experience of painful endometriosis

Background: Endometriosis is a widespread problem in women of reproductive age, causing cyclical and non-cyclical pain in the pelvis and elsewhere, and associated with fatigue, fertility problems, and other symptoms. As a chronic pain problem, psychological variables are important in adjustment and quality of life, but have not been systematically studied. Methods A systematic search of multiple databases was conducted to obtain surveys and qualitative studies of women’s experience of pain from endometriosis. Surveys were combined narratively; qualitative studies were combined by thematic synthesis, and the latter rated for methodological quality. Results: Over 2000 records were screened on title and abstract, and provided 22 surveys and 33 qualitative studies from which accounts could be extracted of the psychological components of pain in endometriosis. Surveys mostly addressed quality of life in endometriosis, with poorer quality of life associated with higher levels of pain and of distress, but few referred to coherent psychological models. Qualitative studies focused rather on women’s experience of living with endometriosis, including trajectories of diagnosis and treatment, with a few addressing meaning and identity. Thematic synthesis provided 10 themes, under the groupings of internal experience of endometriosis (impact on body, emotions, and life); interface with the external world (through self-regulation and social regulation); effects on interpersonal and social life, and encounters with medical care. Conclusions: The psychological components of pain from endometriosis only partly corresponded with standard psychological models of pain, derived from musculoskeletal pain studies, with fewer fears about physical integrity and more about difficulties of managing pain and other symptoms in social settings, including work. Better understanding of the particular psychological threats of endometriosis, and integration of this understanding into medical care with opportunities for psychologically-based pain management, would substantially improve the experience and quality of life of women with painful endometriosis

Reviewing outcomes of psychological interventions with torture survivors: Conceptual, methodological and ethical Issues

Background: Torture survivors face multiple problems, including psychological difficulties, whether they are refugees or remain in the country where they were tortured. Provision of rehabilitation varies not only with the needs of survivors and resources available but also with service models, service provider preferences and the local and country context. Despite increasing efforts in research on the effectiveness of psychological interventions with torture survivors, results are inconclusive. Methods: We undertook a Cochrane systematic review of psychological, social and welfare provision, with meta-analysis to best estimate efficacy. The process raised conceptual, methodological and ethical issues of relevance to the wider field. Findings: We searched very widely, but rejected hundreds of papers which recommended treatment without providing evidence. We found nine randomized controlled trials, from developed and under-resourced settings. All conceptualized survivors’ problems in psychiatric terms, using outcomes of post-traumatic stress symptoms, distress, and quality of life, by self-report, with or without translation or unstandardized interpretation, and with little mention of cultural or language issues. None used social or welfare interventions. Four related studies used narrative exposure therapy (NET) in a brief form, and without ensuring a safe setting as recommended. Five used mixed methods, including exposure, cognitive behavioral therapy, and eye movement desensitization. Combined, the studies showed no immediate improvement in PTSD, distress, or quality of life; at six months follow-up, a minority showed some improvement in PTSD and distress, although participants remained severely affected. Conclusions: While applauding researchers’ commitment in running these trials, we raise ethical issues about exposure in particular, and about the effects of shortcomings in methodology, particularly around assessment using unfamiliar cultural frameworks and language, and the lack of concern about dropout which may indicate harm. The issues addressed aid interpretation of existing research, and guide clinical practice as well as future studies evaluating its effectiveness.   &nbsp

Exploration of Hospital Inpatients' Use of the Verbal Rating Scale of Pain

Background: Assessment of pain largely relies on self-report. Hospitals routinely use pain scales, such as the Verbal Rating Scale (VRS), to record patients' pain, but such scales are unidimensional, concatenating pain intensity and other dimensions of pain with significant loss of clinical information. This study explored how inpatients understand and use the VRS in a hospital setting. Methods: Forty five participants were interviewed, with data analysed by thematic analysis, and completed a task concerned with the VRS and communication of other dimensions of pain. Results: Participants anchored their pain experience in the physical properties of pain, its tolerability, and its impact on functioning. Their relationship to analgesic medication, personal coping styles, and experiences of staff all influenced how they used the VRS to communicate their pain. Conclusion: Participants grounded and explained their pain in semantically similar but idiosyncratic ways. The VRS was used to combine pain intensity with multiple other elements of pain and often as a way to request analgesic medication. Pain scores need to be explored and elaborated by patient and staff, content of which will imply access to non-pharmacological resources to manage pain

Learning Bodily and Temporal Attention in Protective Movement Behavior Detection

For people with chronic pain, the assessment of protective behavior during physical functioning is essential to understand their subjective pain-related experiences (e.g., fear and anxiety toward pain and injury) and how they deal with such experiences (avoidance or reliance on specific body joints), with the ultimate goal of guiding intervention. Advances in deep learning (DL) can enable the development of such intervention. Using the EmoPain MoCap dataset, we investigate how attention-based DL architectures can be used to improve the detection of protective behavior by capturing the most informative temporal and body configurational cues characterizing specific movements and the strategies used to perform them. We propose an end-to-end deep learning architecture named BodyAttentionNet (BANet). BANet is designed to learn temporal and bodily parts that are more informative to the detection of protective behavior. The approach addresses the variety of ways people execute a movement (including healthy people) independently of the type of movement analyzed. Through extensive comparison experiments with other state-of-the-art machine learning techniques used with motion capture data, we show statistically significant improvements achieved by using these attention mechanisms. In addition, the BANet architecture requires a much lower number of parameters than the state of the art for comparable if not higher performances.Comment: 7 pages, 3 figures, 2 tables, code available, accepted in ACII 201

Chronic-Pain Protective Behavior Detection with Deep Learning

In chronic pain rehabilitation, physiotherapists adapt physical activity to patients' performance based on their expression of protective behavior, gradually exposing them to feared but harmless and essential everyday activities. As rehabilitation moves outside the clinic, technology should automatically detect such behavior to provide similar support. Previous works have shown the feasibility of automatic protective behavior detection (PBD) within a specific activity. In this paper, we investigate the use of deep learning for PBD across activity types, using wearable motion capture and surface electromyography data collected from healthy participants and people with chronic pain. We approach the problem by continuously detecting protective behavior within an activity rather than estimating its overall presence. The best performance reaches mean F1 score of 0.82 with leave-one-subject-out cross validation. When protective behavior is modelled per activity type, performance is mean F1 score of 0.77 for bend-down, 0.81 for one-leg-stand, 0.72 for sit-to-stand, 0.83 for stand-to-sit, and 0.67 for reach-forward. This performance reaches excellent level of agreement with the average experts' rating performance suggesting potential for personalized chronic pain management at home. We analyze various parameters characterizing our approach to understand how the results could generalize to other PBD datasets and different levels of ground truth granularity.Comment: 24 pages, 12 figures, 7 tables. Accepted by ACM Transactions on Computing for Healthcar