Pain sensation is essential for survival, since it draws attention to physical threat to the body. Pain assessment is usually done through self-reports. However, self-assessment of pain is not available in the case of noncommunicative patients, and therefore, observer reports should be relied upon. Observer reports of pain could be prone to errors due to subjective biases of observers. Moreover, continuous monitoring by humans is impractical. Therefore, automatic pain detection technology could be deployed to assist human caregivers and complement their service, thereby improving the quality of pain management, especially for noncommunicative patients. Facial expressions are a reliable indicator of pain, and are used in all observer-based pain assessment tools. Following the advancements in automatic facial expression analysis, computer vision researchers have tried to use this technology for developing approaches for automatically detecting pain from facial expressions. This paper surveys the literature published in this field over the past decade, categorizes it, and identifies future research directions. The survey covers the pain datasets used in the reviewed literature, the learning tasks targeted by the approaches, the features extracted from images and image sequences to represent pain-related information, and finally, the machine learning methods used.

Background: Over the last decades, a considerable number of observational scales have been developed to assess pain in persons with dementia. The time seems ripe now to build on the knowledge and expertize implemented in these scales to form an improved, “best‐of” meta‐tool. The EU‐COST initiative “Pain in impaired cognition, especially dementia” aimed to do this by selecting items out of existing observational scales and critically re‐assessing their suitability to detect pain in dementia. This paper reports on the final phase of this collaborative task.Methods: Items from existing observational pain scales were tested for “frequency of occurrence (item difficulty),” “reliability” and “validity.” This psychometric testing was carried out in eight countries, in different healthcare settings, and included clinical as well as experimental pain conditions.Results: Across all studies, 587 persons with dementia, 27 individuals with intellectual disability, 12 Huntington's disease patients and 59 cognitively healthy controls were observed during rest and movement situations or while receiving experimental pressure pain, respectively. The psychometric outcomes for each item across the different studies were evaluated within an international and multidisciplinary team of experts and led a final selection of 15 items (5x facial expressions, 5x body movements, 5x vocalizations).Conclusions: The final list of 15 observational items have demonstrated psychometric quality and clinical usefulness both in their former scales and in the present international evaluation; accordingly, they qualified twice to form a new internationally agreed‐on meta‐tool for Pain Assessment in Impaired Cognition, the PAIC‐15 scale.Significance: Using a meta‐tool approach by building on previous observational pain assessment scales and putting the items of these scales through rigorous empirical testing (using experimental as well as clinical pain studies in several European countries), we were able to identify the best items for pain assessment in individuals with impaired cognition. These selected items form the novel PAIC15 scale (pain assessment in impaired cognition, 15 items).

Purpose of review: The COVID-19 outbreak has had major impact on individual's psychological health and overall well being worldwide. Evidence shows that these psychological challenges are especially prominent in healthcare workers (HCW); especially in nurses. Indeed, several studies report that nurses suffer more psychologically because of the consequences of the pandemic compared with medical doctors. To further look into this, we systematically review the recent literature to see whether the psychological impact of the COVID-19 pandemic differs between medical doctors and nurses across studies and which aspects of mental health are especially affected in nurses. Recent findings: Across studies, there is solid evidence that nurses show poorer mental health outcomes compared with medical doctors during the COVID-19 pandemic. This is especially true for symptoms of depression, anxiety and posttraumatic stress disorder (PTSD). Here, prevalence rates in nurses are often higher than 50%. In contrast, general stress levels and burnout seem to be comparable between nurses and medical doctors. Summary: Given that nurses suffer more from depression, anxiety and PTSD symptoms during the COVID-19 pandemic, special programs addressing their needs are required.

Facial expressions of pain are composed of a subset of pain-indicative muscle movements. Amongst this subset, contracting the muscles surrounding the eyes (orbicularis oculi muscle) is the most frequent response and has been linked specifically to pain intensity, a fundamental aspect of the sensory dimension of pain. To further explore this link, the present study used functional magnetic resonance imaging (fMRI) to test the hypothesis that orbicularis oculi activation during pain reflects the magnitude of brain responses in areas being involved in processing the sensory dimension of pain. Facial and brain (BOLD) responses to experimentally-induced heat pain applied to the left lower leg were assessed in twenty-two healthy participants after verbal suggestions were given to specifically increase perceived pain intensity and in control conditions involving no suggestion. Increases in pain intensity produced the expected changes in facial responses characterized by a stronger contraction of the orbicularis oculi muscle. A regression model further demonstrated that stronger increases in orbicularis oculi activity reflected a larger increase in the BOLD response to the noxious stimulus in the leg area of the primary somatosensory cortex (S1) and a larger decrease in medial prefrontal activity consistent with previous finding suggesting disinhibition. Importantly, the positive coupling of orbicularis oculi with S1 activity was not accounted for by changes in other facial muscles. These results are consistent with the notion that facial expressions of pain differentially encode the multi-dimensional pain experience and reflect, at least partly, the activity of the spino-thalamo-cortical pathway targeting the primary somatosensory cortex.

Background: Facial activity during pain is composed of varying combinations of a few elementary facial responses (so‐called Action Units). A previous study of experimental pain showed that these varying combinations can be clustered into distinct facial activity patterns of pain. In the present study, we examined whether comparable facial activity patterns can also be identified among people suffering from clinical pain; namely, shoulder pain.Methods: Facial expressions of patients suffering from shoulder pain (N = 126) were recorded while twice undergoing a battery of passive range‐of‐motion tests to their affected limbs (UNBC‐McMaster Shoulder Pain Expression Archive Database), which elicited peaks of acute pain. Facial expressions were analysed using the Facial Action Coding System to extract facial Action Units (AUs). Hierarchical cluster analyses were used to look for characteristic combinations of these AUs.Results: Cluster analyses revealed four distinct activity patterns during painful movements. Each cluster was composed of different combinations of pain‐indicative AUs, with one AU common to all clusters, namely, “narrowed eyes”. Besides these four clusters, there was a “stoic” pattern, characterized by no discernible facial action. The identified clusters were relatively stable across time and comparable to the facial activity patterns found previously for experimental heat pain.Conclusions: These findings corroborate the hypothesis that facial expressions of acute pain are not uniform. Instead, they are composed of different combinations of pain‐indicative facial responses, with one omnipresent response, namely, “narrowed eyes”. Raising awareness about these inter‐individually different “faces of pain” could improve the recognition and, thereby, its diagnostic training for professionals, like nurses and physicians.Significance: Similar to experimental pain, facial activity during evoked pain episodes in shoulder pain patients could be clustered into distinct faces of pain. Each cluster was composed of different combinations of single facial responses, namely: narrowed eyes, which is displayed either alone or in combination with opened mouth or wrinkled nose, or furrowed brows and closed eyes. These distinct faces of pain may inform the training of professionals and computers how to best recognize pain based on facial expressions.

Studies of facial responses during experimental and clinical pain have revealed a surprising phenomenon, namely, that a considerable number of individuals respond with a smile. So far, it is not known why smiling occurs during pain. It is possible that the “smile of pain” is socially motivated (e.g., reinforcing social bonds while undergoing an unpleasant experience). The present studies were conducted in an attempt to address the role of social motives in smiling during pain. In two studies, we varied the quantitative (level of sociality) and qualitative (properties of the relationship between interactants) components of the situations in which participants received painful stimulation. Participants’ faces were video-recorded and the occurrence of smiling was assessed. The occurrence of smiling differed depending on stimulus intensity and the properties of the relationship between interactants. Smiling occurred more often during the painful compared to nonpainful stimulation. Whereas the presence of a stranger (experimenter) reduced the smiling behavior, the presence of an intimate other increased it. Slight variations in the level of sociality, however, had no effect on the degree of smiling. Social motives possibly aimed at strengthening social bonds and thus ensuring social support appear to underlie smiling during pain.