Elevated pain threshold in anorexia nervosa subjects

Perceptual Dysfunction in Eating Disorders

Eating disorders (EDs) are characterized by abnormal responses to food and weight-related stimuli and are associated with significant distress, impairment, and poor outcomes. Because many of the cardinal symptoms of EDs involve disturbances in perception of one's body or abnormal affective or cognitive reactions to food intake and how that affects one's size, there has been longstanding interest in characterizing alterations in sensory perception among differing ED diagnostic groups. Within the current review, we aimed to critically assess the existing research on exteroceptive and interoceptive perception and how sensory perception may influence ED behavior. Overall, existing research is most consistent regarding alterations in taste, visual, tactile, and gastric-specific interoceptive processing in EDs, with emerging work indicating elevated respiratory and cardiovascular sensitivity. However, this work is far from conclusive, with most studies unable to speak to the precise etiology of observed perceptual differences in these domains and disentangle these effects from affective and cognitive processes observed within EDs. Further, existing knowledge regarding perceptual disturbances in EDs is limited by heterogeneity in methodology, lack of multimodal assessment protocols, and inconsistent attention to different ED diagnoses. We propose several new avenues for improving neurobiology-informed research on sensory processing to generate actionable knowledge that can inform the development of innovative interventions for these serious disorders.

Abnormal sense of agency in eating disorders

The feeling of controlling one's own actions and, through them, impacting the external environment (i.e. Sense of Agency-SoA) can be relevant in the eating disorders (EDs) symptomatology. Yet, it has been poorly investigated. This study aims to implicitly assess SoA exploiting the Sensory Attenuation paradigm in two groups of EDs patients (Anorexia Nervosa Restrictive and Anorexia Nervosa Binge-Purging or Bulimia Nervosa) compared to a control group. We find that controls perceive self-generated stimuli as less intense than other-generated ones showing the classic pattern of sensory attenuation. By contrast, EDs patients show the opposite pattern, with self-generated perceived as more intense than other-generated stimuli. This result indicates an alteration of the implicit component of the feeling of control in EDs patients, thus suggesting a potential implication of these results for the clinical practice and the treatment of EDs symptomatology.

Interoceptive Awareness and Suicidal Ideation in a Clinical Eating Disorder Sample: The Role of Body Trust

Previous research has demonstrated that both suicidal ideation (SI) and eating disorders (EDs) are associated with poor interoceptive awareness (IA). Suicidality research has demonstrated that the IA dimension of lower body trust is associated with SI, suicide plans, and suicide attempts. Similarly, in ED samples, recent research supports that low body trust has been the most robust dimension of IA associated with eating pathology. However, to date, research is lacking in how dimensions of IA may be associated with SI in an ED sample, above and beyond the impact of eating pathology on SI. Thus, in a clinical ED sample, the present study sought to determine which IA dimensions predict the presence and severity of SI, above and beyond ED symptoms. Participants (N = 102) completed a clinical interview assessing SI and self-report assessments including the Multidimensional Assessment of Interoceptive Awareness (MAIA). Results demonstrated that patients with current SI reported greater ED psychopathology, lower MAIA Attention Regulation, MAIA Self-Regulation, and MAIA Trusting scores compared to patients without SI. Higher ED psychopathology and lower MAIA Attention Regulation, Self-Regulation, and Trusting subscale scores were all significantly associated with the presence of SI. However, only low MAIA Trusting scores predicted the presence of SI, above and beyond covariates (age, depression, and eating pathology). No MAIA subscales were correlated with the severity of SI. Consistent with previous research, results suggest low MAIA Trusting scores may be associated with SI in ED samples and highlight the need for future research on mechanisms of these associations.

Pain Processing in Psychiatric Conditions: A Systematic Review

Pain is a universal, multidimensional experience with sensory, emotional, cognitive, and social components, which is fundamental to our environmental learning when functioning typically. Understanding pain processing in psychiatric conditions could provide unique insight into the underlying pathophysiology or psychiatric disease, especially given the psychobiological overlap with pain processing pathways. Studying pain in psychiatric conditions is likely to provide important insights, yet, there is a limited understanding beyond the work in depression and anxiety. This is a missed opportunity to describe psychiatric conditions in terms of neurobiological alterations. To examine the research into the pain experiences of these groups and the extent to which a-typicality is present, a systematic review was conducted. An electronic search strategy was developed and conducted in several databases. The current systematic review included 46 studies covering five Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) disorders: autism, attention-deficit hyperactivity disorder (ADHD), schizophrenia, personality disorder, and eating disorders, confirming tentative evidence of altered pain and touch processing. Specifically, hyposensitivity is reported in schizophrenia, personality disorder and eating disorder, hypersensitivity in ADHD, and mixed results for autism. Review of the research highlights a degree of methodological inconsistency in the utilization of comprehensive protocols, the lack of which fails to allow us to understand whether a-typicality is systemic or modality specific.

The effect of intranasal oxytocin on the perception of affective touch and multisensory integration in anorexia nervosa: protocol for a double-blind placebo-controlled crossover study

INTRODUCTION

Anorexia nervosa (AN) is an eating disorder characterised by restriction of energy intake, fears of gaining weight and related body image disturbances. The oxytocinergic system has been proposed as a pathophysiological candidate for AN. Oxytocin is a neuropeptide involved in bodily processes (eg, breast feeding) and in the onset of social behaviours (eg, bonding). Studies investigating the effect of intranasal oxytocin (IN-OT) in AN showed that it can improve attentional bias for high-calorie food and fat bodies stimuli, and related stress. However, less is known about the effect of IN-OT on bodily awareness and body image distortions, key features of the disorder linked to its development, prognosis and maintenance. Here, we aim to investigate the effect of IN-OT on the perception of affective, C-tactile-optimal touch, known to be impaired in AN and on multisensory integration processes underlying a body ownership illusion (ie, rubber hand illusion). For exploratory purposes, we will also investigate the effect of IN-OT on another interoceptive modality, namely cardiac awareness and its relationship with affective touch.

DESIGN, METHODS AND ANALYSIS

Forty women with AN and forty matched healthy controls will be recruited and tested in two separate sessions; self-administering IN-OT (40 IU) or placebo, intranasally, in a pseudo-randomised manner. The data from this double-blind, placebo-controlled, cross-over study will be analysed using linear mixed models that allow the use of both fixed (treatment levels) and random (subjects) effects in the same analysis. To address our main hypotheses, separate analyses will be run for the affective touch task, where the primary outcome dependent variable will be the pleasantness of the touch, and for the rubber hand illusion, where we will investigate multisensory integration quantified as subjective embodiment towards the rubber hand. In the latter, we will manipulate the synchronicity of touch and the size of the hand.

ETHICS AND DISSEMINATION

Ethics approval has been obtained by National Research Ethics Service NRES Committee London (Queen's Square Committee, ref number 14/LO/1593). The results will be disseminated through conference presentations and publication in peer-reviewed journals.

Neural hypersensitivity to pleasant touch in women remitted from anorexia nervosa

Interoception, or the sensing and integration of bodily state signals, has been implicated in anorexia nervosa (AN), given that the hallmark symptoms involve food restriction and body image disturbance. Here we focus on brain response to the anticipation and experience of affective interoceptive stimuli. Women remitted from AN (RAN; N = 18) and healthy comparison women (CW; N = 26) underwent a pleasant affective touch paradigm consisting of gentle strokes with a soft brush administered to the forearm or palm during functional neuroimaging. RAN had a lower brain response relative to CW during anticipation of touch, but a greater response when experiencing touch in the right ventral mid-insula. In RAN, this reduced anticipatory response was associated with higher levels of harm avoidance. Exploratory analyses in RAN also suggested that lower response during touch anticipation was associated with greater body dissatisfaction and higher perceived touch intensity ratings. This reduced responsivity to the anticipation of pleasant affective interoceptive stimuli in association with higher harm avoidance, along with an elevated response to the experience of touch, suggests an impaired ability in AN to predict and interpret incoming physiological stimuli. Impaired interoception may thus impact one's sense of self, thereby supporting observations of disturbed body image and avoidance of affective and social stimuli. Therapeutic approaches that help AN to better anticipate and interpret salient affective stimuli or improve tolerance of interoceptive experiences may be an important addition to current interventions.

Does the interpersonal-Psychological theory of suicide provide a useful framework for understanding suicide risk among eating disorder patients? A test of the validity of the IPTS

OBJECTIVE

The current study tested whether the Interpersonal-Psychological Theory of Suicide (IPTS) provides a useful framework for understanding elevated suicide rates among individuals with eating disorders (EDs).

METHOD

Based on predictions of the IPTS, we tested whether the combination of thwarted belongingness and perceived burdensomeness was associated with suicidal desire, and whether the combination of thwarted belongingness, perceived burdensomeness, and fearlessness about death was associated with past suicide attempts in an ED sample (n = 100). We also compared these IPTS constructs in an ED sample versus general psychiatric inpatients (n = 85) and college students (i.e., non-clinical comparison group; n = 93).

RESULTS

Within the ED sample, no hypothesized interactions were found, but perceived burdensomeness was associated with suicidal desire, and perceived burdensomeness and fearlessness about death were associated with past suicide attempts. The ED and psychiatric samples had greater thwarted belongingness, perceived burdensomeness, and suicidal desire than the non-clinical comparison group.

DISCUSSION

The IPTS constructs of perceived burdensomeness and fearlessness about death appear to explain some facets of suicidality among people with EDs, but overall, support for the IPTS was limited. Future research on EDs and suicidality should look beyond the IPTS and consider other biological and sociocultural factors for suicide. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:1082-1086).

The perception of affective touch in anorexia nervosa

Anorexia nervosa (AN) is a disorder characterized by restricted eating, fears of gaining weight, and body image distortions. The etiology remains unknown; however impairments in social cognition and reward circuits contribute to the onset and maintenance of the disorder. One possibility is that AN is associated with reduced perceived pleasantness during social interactions. We therefore examined the perception of interpersonal, 'affective touch' and its social modulation in AN. We measured the perceived pleasantness of light, dynamic stroking touches applied to the forearm of 25 AN patients and 30 healthy controls using C Tactile (CT) afferents-optimal (3cm/s) and non-optimal (18cm/s) velocities, while simultaneously displaying images of faces showing rejecting, neutral and accepting expressions. CT-optimal touch, but not CT non-optimal touch, elicited significantly lower pleasantness ratings in AN patients compared with healthy controls. Pleasantness ratings were modulated by facial expressions in both groups in a similar fashion; namely, presenting socially accepting faces increased the perception of touch pleasantness more than neutral and rejecting faces. Our findings suggest that individuals with AN have a disordered, CT-based affective touch system. This impairment may be linked to their weakened interoceptive perception and distorted body representation.

Abnormal functional global and local brain connectivity in female patients with anorexia nervosa

BACKGROUND

Previous resting-state functional connectivity studies in patients with anorexia nervosa used independent component analysis or seed-based connectivity analysis to probe specific brain networks. Instead, modelling the entire brain as a complex network allows determination of graph-theoretical metrics, which describe global and local properties of how brain networks are organized and how they interact.

METHODS

To determine differences in network properties between female patients with acute anorexia nervosa and pairwise matched healthy controls, we used resting-state fMRI and computed well-established global and local graph metrics across a range of network densities.

RESULTS

Our analyses included 35 patients and 35 controls. We found that the global functional network structure in patients with anorexia nervosa is characterized by increases in both characteristic path length (longer average routes between nodes) and assortativity (more nodes with a similar connectedness link together). Accordingly, we found locally decreased connectivity strength and increased path length in the posterior insula and thalamus.

LIMITATIONS

The present results may be limited to the methods applied during preprocessing and network construction.

CONCLUSION

We demonstrated anorexia nervosa-related changes in the network configuration for, to our knowledge, the first time using resting-state fMRI and graph-theoretical measures. Our findings revealed an altered global brain network architecture accompanied by local degradations indicating wide-scale disturbance in information flow across brain networks in patients with acute anorexia nervosa. Reduced local network efficiency in the thalamus and posterior insula may reflect a mechanism that helps explain the impaired integration of visuospatial and homeostatic signals in patients with this disorder, which is thought to be linked to abnormal representations of body size and hunger.

The joint influence of acquired capability for suicide and stoicism on over-exercise among women

We investigated longitudinal relationships among eating disorder behaviors, stoicism, and the acquired capability for suicide (ACS), which is a construct comprised of pain tolerance and fearlessness about death. University students (n=150) completed assessments measuring stoicism, ACS, and eating disorder behaviors at two time points approximately 30days apart. Among women, there was a quadratic relationship between ACS and over-exercise behaviors, such that as ACS increased the positive association between ACS and over-exercise became more pronounced. Further, among women, ACS moderated the relationship between stoicism and over-exercise, such that high levels of ACS in combination with stoicism predicted increases in over-exercise. Results suggest that ACS in combination with stoicism may lead women to engage in more eating disordered behaviors, like over-exercise.

Fasting and acquired capability for suicide: a test of the interpersonal-psychological theory of suicide in an undergraduate sample

Though some preliminary research within the framework of the interpersonal-psychological theory of suicide (IPTS; Joiner, 2005) has postulated that restrictive eating may contribute to increased risk for suicide through its effect on the acquired capability for suicide (ACS; i.e., increased fearlessness about death and heightened physical pain tolerance), existing studies have not conducted direct tests of this relationship. To enhance understanding of this relationship, we compared undergraduates who endorsed one form of restrictive eating, fasting, (n = 99) to controls endorsing no forms of eating pathology over the lifetime (n = 94). We hypothesized that the fasting group would have higher ACS and higher likelihood of suicide attempt history. Contrary to hypotheses, no differences emerged between groups on ACS, and frequency of fasting within the fasting group was not significantly associated with ACS. Consistent with hypotheses, the fasting group was more likely to have suicide attempt history. Though results were not entirely consistent with hypotheses, the current study represents the first attempt at isolating and examining one form of restrictive eating (i.e., fasting) within the context of the IPTS. Results suggest that, in isolation, fasting may not be directly contributing to increases in ACS.

Reduced functional connectivity in the thalamo-insular subnetwork in patients with acute anorexia nervosa

The neural underpinnings of anorexia nervosa (AN) are poorly understood. Results from existing functional brain imaging studies using disorder-relevant food- or body-stimuli have been heterogeneous and may be biased due to varying compliance or strategies of the participants. In this study, resting state functional connectivity imaging was used. To explore the distributed nature and complexity of brain function we characterized network patterns in patients with acute AN. Thirty-five unmedicated female acute AN patients and 35 closely matched healthy female participants underwent resting state functional magnetic resonance imaging. We used a network-based statistic (NBS) approach [Zalesky et al., 2010a] to identify differences between groups by isolating a network of interconnected nodes with a deviant connectivity pattern. Group comparison revealed a subnetwork of connections with decreased connectivity including the amygdala, thalamus, fusiform gyrus, putamen and the posterior insula as the central hub in the patient group. Results were not driven by changes in intranodal or global connectivity. No network could be identified where AN patients had increased coupling. Given the known involvement of the identified thalamo-insular subnetwork in interoception, decreased connectivity in AN patients in these nodes might reflect changes in the propagation of sensations that alert the organism to urgent homeostatic imbalances and pain-processes that are known to be severely disturbed in AN and might explain the striking discrepancy between patient's actual and perceived internal body state.

The expression of cytokines and chemokines in the blood of patients with severe weight loss from anorexia nervosa: an exploratory study

Anorexia nervosa (AN) is a serious, potentially life-threatening disorder characterized by severe weight loss, dysregulated eating, and often excessive exercise. While psychiatric illnesses such as depression are associated with increased levels of pro-inflammatory mediators, evidence for such disturbances in patients with AN has been less clear. In an exploratory study of possible disturbances in immune responses in AN, we assayed a panel of cytokines and chemokines in the blood of patients undergoing inpatient treatment, testing the hypothesis that metabolic disturbances in this disease would lead to a pattern of immune disturbances distinct from that of other psychiatric diseases. For this purpose, we evaluated patients by the Beck Depression Inventory-II (BDI-II) and the Eating Disorders Examination-Questionnaire and assessed cytokines and chemokines by enzyme-linked immunosorbent assays. Patients reported a moderate level of depression (mean BDI-II = 22.6) but exhibited few immunologic abnormalities of the kind associated with major depressive disorder [e.g., increased interleukin (IL)-6]; RANTES showed the most frequent elevations and was increased in 4 of the patients studied. Together, these findings suggest that features of AN such as loss of adipose tissue and excessive exercise may attenuate cytokine production and thus modulate the experience of illness that impacts on core features of disease.

Insular dysfunction and descending pain inhibition in anorexia nervosa

OBJECTIVE

Reduced perception of pain is a well-established phenomenon in patients with anorexia nervosa (AN). We tested the hypothesis that altered processing of pain within the insula might account for reduced perception of pain.

METHOD

Heat pain thresholds were obtained in nineteen patients with AN and matched controls. Thereafter, a thermode was used to deliver thermal painful stimuli to the right arm during functional magnetic resonance imaging (fMRI) measurements. Stimuli were initiated for 10 s from a baseline resting temperature (32°C) to three different levels (37, 42, 45°C).

RESULTS

Significantly increased heat pain thresholds were observed in patients. A stronger activation during heat pain perception was found in the left posterior insula in controls. In contrast, higher levels of activity were shown in the ipsilateral pons in patients when compared to controls. In patients, we found a significant interrelation between the depression score (Beck depression inventory) and heat pain activations.

CONCLUSION

We suggest that reduced activity in the left posterior insula might contribute to increased pain thresholds in patients, while increased activations in the right anterior insula and pons mirror augmented sympathetic modulation putatively related to amplification of adrenergic descending pain inhibition. In addition, pain thresholds and brain activations were influenced by disease-inherent depressed mood.

Altered insula activation during pain anticipation in individuals recovered from anorexia nervosa: evidence of interoceptive dysregulation

OBJECTIVE

Recent evidence raises the possibility that symptoms of anorexia nervosa (AN) could be related to impaired interoception. Pain is an interoceptive process with well-characterized neuroanatomical pathways that may overlap to a large degree with neural systems that may be dysregulated in individuals with AN, such as the insula.

METHOD

Functional magnetic resonance imaging (fMRI) was used to assess neural substrates of pain anticipation and processing in 10 healthy control women (CW) and 12 individuals recovered from AN (REC AN) in order to avoid the confounding effects of malnutrition. Painful heat stimuli were applied while different colors signaled the intensity of the upcoming stimuli.

RESULTS

REC AN compared with CW showed greater activation within right anterior insula (rAI), dorsolateral prefrontal cortex (dlPFC) and cingulate during pain anticipation, and greater activation within dlPFC and decreased activation within posterior insula during painful stimulation. Greater anticipatory rAI activation correlated positively with alexithymic feelings in REC AN participants.

DISCUSSION

REC AN showed a mismatch between anticipation and objective responses, suggesting altered integration and, possibly, disconnection between reported and actual interoceptive state. Alexithymia assessment provided additional evidence of an altered ability to accurately perceive bodily signals in women recovered from AN.

Thresholds and tolerance of physical pain among young adults who self-injure

Prevalence rates of nonsuicidal self-injury among college students range from 17% to 38%. Research indicates that individuals with borderline personality disorder who self-injure sometimes report an absence of pain during self-injury. Furthermore, self-injury in the absence of pain has been associated with more frequent suicide attempts. The present study examined pain thresholds and tolerance among 44 college students (11 who engaged in self-injury and 33 who did not). Pain thresholds and tolerance were measured using an algometer pressure device that was used to produce pain in previous laboratory research. Participants who engaged in self-injury had a higher pain tolerance than those who did not. In addition, participants who engaged in self-injury rated the pain as less intense than participants who did not. ANCOVAs revealed that depression was associated with pain rating and pain tolerance.

Deaths by suicide among individuals with anorexia as arbiters between competing explanations of the anorexia-suicide link

BACKGROUND

Suicide is a leading cause of death among individuals with anorexia nervosa (AN). In this paper, we examined competing explanations of the high rate of death by suicide among individuals with anorexia nervosa (AN).

METHODS

Nine case reports of individuals with AN who died by suicide were evaluated to determine whether death by suicide occurred a) because physical health was so compromised that what would be a non-lethal suicide attempt in a healthy adult became a fatal suicide attempt, or b) because highly lethal suicide attempts that would have killed any adult, healthy or medically compromised, were made.

RESULTS

The findings converged with the latter hypothesis, as predicted by Joiner's [Joiner, T., 2006. Why People Die By Suicide. Harvard University Press, Cambridge, MA] theory of suicide, which suggests individuals with AN may habituate to the experience of pain during the course of their illness and accordingly die by suicide using methods that are highly lethal.

LIMITATIONS

This study utilized case reports instead of an experimental design, which impedes its ability to comment on whether there is a causal relationship between Joiner's theory and death by suicide among individuals with AN.

CONCLUSIONS

Clinicians are encouraged to carefully assess suicidality in AN patients, paying particular attention to issues related to lethality.

Motor- and food-related metabolic cerebral changes in the activity-based rat model for anorexia nervosa: a voxel-based microPET study

Anorexia nervosa (AN) is a disorder that is difficult to treat with psycho- or pharmacotherapy. In order to identify involved neurocircuitry, we investigated the cerebral metabolic alterations in the activity-based anorexia (ABA) rat model, where restriction of the food intake period induces hyperactivity and decreased body weight. Cerebral (18)F-fluorodeoxyglucose uptake was investigated in rats in the activity-based anorexia model (n=9) and compared to controls (n=10), using a CTI Focus microPET 220. Regional metabolic changes were investigated using statistical parametric mapping (SPM2) and correlated to weight and hyperactivity measures on a voxel-by-voxel basis. Higher regional metabolism was found in ABA rats in the mediodorsal thalamus, ventral pontine nuclei and cerebellum, while hypometabolism was seen in the left rhinal and bilateral insular cortex, and bilateral ventral striatum (p<0.001). A positive correlation was observed between body weight loss and brain metabolism in the cingulate cortex and surrounding motor and somatosensory cortex (p<0.001). Thus, in the ABA model metabolic changes are present in brain areas related to disease status and weight loss, which share several characteristics with the human disease.

Gastrointestinal complaints in patients with eating disorders

BACKGROUND

Patients with eating disorders (EDs) typically have numerous somatic and gastrointestinal complaints. Early referral to treatment may result in improved outcomes. We sought to determine whether patients with EDs were presenting to gastroenterologists or primary care physicians with gastrointestinal complaints early in the disease course, when referral for specialized, comprehensive treatment would be most beneficial.

STUDY

Over a 1-year period, we administered a structured interview to a cohort of patients presenting for inpatient ED treatment. We also conducted the same interview on an age-matched cohort of medical students to determine baseline incidences of various gastrointestinal healthcare behaviors.

RESULTS

Patients with bulimia nervosa were significantly more likely to seek healthcare for a gastrointestinal complaint before seeking treatment for an ED than were controls. Patients with EDs were significantly more likely to be prescribed medication for the gastrointestinal tract than were controls.

CONCLUSION

Gastroenterologists and primary care physicians should employ available instruments to screen young women of low to normal weight with gastrointestinal complaints for possible EDs. Referral to specialized treatment programs should be made promptly when an ED is identified.

Changes of pain perception, autonomic function, and endocrine parameters during treatment of anorectic adolescents

OBJECTIVES

The underlying mechanisms of reduced pain perception in anorexia nervosa (AN) are unknown. To gain more insight into the pathology, the authors investigated pain perception, autonomic function, and endocrine parameters before and during successful treatment of adolescent AN patients.

METHOD

Heat pain perception was assessed in 15 female adolescent AN patients and matched controls. Results were correlated with autonomic and endocrine parameters (free triiodothyronine, free cortisol). Autonomic function was studied using heart rate variability and pupillary light reflex assessment. To investigate the influence of therapy on these parameters, data were obtained at three different time points.

RESULTS

Heat pain thresholds were significantly increased in the acute state and decreased after weight had been regained for 6 months. Similarly, an increased parasympathetic tone was present in the acute state only. The relative amplitude of the pupillary light reflex showed a positive correlation to pain thresholds over time and predicted disease progression. In addition, the authors found a negative correlation between increased pain thresholds and low free cortisol.

CONCLUSION

Increased pain thresholds are associated with increased parasympathetic tone and a hypothyroid state in AN. This may either indicate common central mechanisms or suggest a causative interaction.

Pain experience related to self-injury in eating disorder patients

A reduced pain sensitivity has been found in eating disorder (ED) patients. These patients often show various types of self-injurious behaviors (SIB) which some experience as painful, while others report analgesia during episodes of SIB. How can we explain these differences? We studied female ED patients (N=185) of whom 84 had admitted some form of SIB in their recent history. The presence/absence of pain report during SIB was not significantly related to the type of ED. The longer the history of SIB, the less pain was reported. Ratings of dissociation and traumatic experiences were higher in patients who did not experience pain while injuring themselves. We discuss several biopsychosocial explanations for these findings with suggestions for future research.

Elevated pain threshold in eating disorders: physiological and psychological factors

Several studies have found decreased pain sensitivity in patients with eating disorders but it is unclear what physiological and psychological factors are associated with this abnormality. In the present investigation, thermal pain threshold latency, somatoform dissociation, body image disturbance and physiological indices of autonomic neural system activity were measured in 39 female patients with eating disorders (21 with anorexia nervosa and 18 with bulimia nervosa) and 17 healthy women. Pain threshold was elevated in patients with eating disorders, especially those with binge-purging symptomatology. A regression analysis indicated that increased pain threshold is moderately associated with decreased peripheral skin temperature and weakly associated with lack of familiarity with one's own body. However, the between group differences in pain perception remained significant after controlling for peripheral skin temperature. Hence, elevation of pain threshold in eating disorders is a replicable finding, which is not explicable by peripheral indices of autonomic system activity or by somatoform dissociation. In future research it may be evaluated as a potential marker of broader phenotype of decreased interoceptive awareness, which may be associated with vulnerability to the development of eating disorders.