Impact of the neural correlates of stress and cue reactivity on stress related binge eating in the natural environment

Molecular and functional mapping of the neuroendocrine hypothalamus: a new era begins

BACKGROUND

Recent advances in neuroscience tools for single-cell molecular profiling of brain neurons have revealed an enormous spectrum of neuronal subpopulations within the neuroendocrine hypothalamus, highlighting the remarkable molecular and cellular heterogeneity of this brain area.

RATIONALE

Neuronal diversity in the hypothalamus reflects the high functional plasticity of this brain area, where multiple neuronal populations flexibly integrate a variety of physiological outputs, including energy balance, stress and fertility, through crosstalk mechanisms with peripheral hormones. Intrinsic functional heterogeneity is also observed within classically 'defined' subpopulations of neuroendocrine neurons, including subtypes with distinct neurochemical signatures, spatial organisation and responsiveness to hormonal cues.

AIM

The aim of this review is to critically evaluate past and current research on the functional diversity of hypothalamic neuroendocrine neurons and their plasticity. It focuses on how this neuronal plasticity in this brain area relates to metabolic control, feeding regulation and interactions with stress and fertility-related neural circuits.

CONCLUSION

Our analysis provides an original framework for improving our understanding of the hypothalamic regulation of hormone function and the development of neuroendocrine diseases.

Better together: A systematic review of studies combining magnetic resonance imaging with ecological momentary assessment

Social neuroscientists often use magnetic resonance imaging (MRI) to understand the relationship between social experiences and their neural substrates. Although MRI is a powerful method, it has several limitations in the study of social experiences, first and foremost its low ecological validity. To address this limitation, researchers have conducted multimethod studies combining MRI with Ecological Momentary Assessment (EMA). However, there are no existing recommendations for best practices for conducting and reporting such studies. To address the absence of standards in the field, we conducted a systematic review of papers that combined the methods. A systematic search of peer-reviewed papers resulted in a pool of 11,558 articles. Inclusion criteria were studies in which participants completed (a) Structural or functional MRI and (b) an EMA protocol that included self-report. Seventy-one papers met inclusion criteria. The following review compares these studies based on several key parameters (e.g., sample size) with the aim of determining feasibility and current standards for design and reporting in the field. The review concludes with recommendations for future research. A special focus is given to the ways in which the two methods were combined analytically and suggestions for novel computational methods that could further advance the field of social neuroscience.

The role of functional and structural properties of the nucleus accumbens subregions in eating behavior regulation of bulimia nervosa

OBJECTIVE

Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. This study investigated the structural and functional properties of NAc in patients with BN.

METHOD

Based on the resting-state functional MRI and high-resolution anatomical T1-weighted imaging data acquired from 43 right-handed BN patients and 40 sex-, age- and education-matched right-handed healthy controls (HCs), the group differences in gray matter volume (GMV) and fractional amplitude of low-frequency fluctuation (fALFF) in slow-4 and -5 bands and functional connectivity (FC) of NAc subregions (core and shell) were compared. The relationships between MRI and clinical data were explored in the BN group.

RESULTS

Compared with HCs, BN patients showed preserved GMV, decreased fALFF in slow-5 band of the left NAc core and shell, decreased FC between left NAc core and right caudate, and increased FC between all NAc subregions and frontal regions, between all NAc subregions (except the right NAc core) and the supramarginal gyrus (SMG), and between right NAc shell and left middle temporal gyrus. FC between the NAc and SMG was correlated with emotional eating behaviors.

DISCUSSION

Our study revealed preserved GMV, local neuronal activity reduction and functional network reorganization of the NAc in BN. The functional network reorganization of the NAc mainly occurred in the frontal cortex and was correlated with emotional eating behavior. These findings may provide novel insights into the BN using NAc as an entry point.

PUBLIC SIGNIFICANCE

Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. We used a multimodal MRI technique to systematically investigate structural and functional alterations in NAc subregions of BN patients and explored the associations between such alterations and maladaptive eating behaviors, hoping to provide novel insights into BN.

The Insidious Influence of Stress: An Integrated Model of Stress, Executive Control, and Psychopathology

Although exposure to acute stress undoubtedly contributes to psychopathology, most individuals do not develop psychopathology following stress exposure. To explain this, biological, emotional, and cognitive responses to stress have been implicated, but individual differences in executive control (i.e., top-down control of cognition and behavior) measured in response to stress has only recently emerged as a potential factor contributing to psychopathology. In this review, we introduce a model-the integrated model of stress, executive control, and psychopathology-positing how the impairing effects of acute stress on executive control can contribute to psychopathology. We link to research on biological, emotional, and cognitive processes, all of which can be impacted by executive control, to propose a framework for how poorer executive control under conditions of acute stress can contribute to psychopathology. This integrated model is intended to further our understanding of who is more susceptible to the negative consequences of stress.

The influence of stress on the neural underpinnings of disinhibited eating: a systematic review and future directions for research

Disinhibited eating involves overconsumption and loss of control over food intake, and underpins many health conditions, including obesity and binge-eating related disorders. Stress has been implicated in the development and maintenance of disinhibited eating behaviours, but the mechanisms underlying this relationship are unclear. In this systematic review, we examined how the impact of stress on the neurobiological substrates of food-related reward sensitivity, interoception and cognitive control explains its role in disinhibited eating behaviours. We synthesised the findings of functional magnetic resonance imaging studies including acute and/or chronic stress exposures in participants with disinhibited eating. A systematic search of existing literature conducted in alignment with the PRISMA guidelines identified seven studies investigating neural impacts of stress in people with disinhibited eating. Five studies used food-cue reactivity tasks, one study used a social evaluation task, and one used an instrumental learning task to probe reward, interoception and control circuitry. Acute stress was associated with deactivation of regions in the prefrontal cortex implicated in cognitive control and the hippocampus. However, there were mixed findings regarding differences in reward-related circuitry. In the study using a social task, acute stress associated with deactivation of prefrontal cognitive control regions in response to negative social evaluation. In contrast, chronic stress was associated with both deactivation of reward and prefrontal regions when viewing palatable food-cues. Given the small number of identified publications and notable heterogeneity in study designs, we propose several recommendations to strengthen future research in this emerging field.

Ecological momentary assessment of state affect prior to and following loss of control eating in young men

OBJECTIVE

Loss of control (LOC) eating is prevalent but understudied among young men. Affect regulation models propose that LOC eating functions as a maladaptive effort to escape from distressing affective states. As such, negative affect is thought to increase before and decrease after LOC eating. However, examinations with young men are lacking and it remains unclear whether specific emotional experiences are differentially implicated in their LOC eating.

METHODS

The current study examined the temporal roles of affect in LOC eating in 31 young men (18-35 years; Mage = 25.74 ± 5.61y; 46.7 % White; 30 % Black/African American; 10 % Hispanic/Latino, 10 % South Asian) who reported engaging in recurrent LOC eating. Participants completed a 14-day ecological momentary assessment protocol and recorded all eating episodes each day and their state affect five times per day. Generalized linear mixed models were conducted to examine the trajectories of global and item-level negative and positive affect pre- and post-LOC eating episodes.

RESULTS

Negative affect did not change significantly before or after LOC eating (ps > .05). Positive affect did not change significantly before LOC eating (ps > .05). Global positive affect, excitement, and happiness decreased significantly after LOC eating (ps ≤ .001).

DISCUSSION

Study findings contradict extant theory and empirical data largely from female samples. Negative affect did not increase risk for LOC eating, nor did LOC eating function to improve participants' mood; rather, positive mood slightly decreased after LOC eating. Further investigation around the observed decline in positive affect after LOC eating will clarify if this is a relevant intervention point in this population.

The association between mental health and Bulimia Nervosa among a sample of Lebanese young adults: the indirect effect of difficulties in emotion regulation

BACKGROUND

Bulimia nervosa (BN) is defined as repeated episodes of binge eating, followed by compensatory behaviors such as self-induced vomiting. BN has been shown to be associated with many co-morbidities including depression and anxiety. BN has also been associated with stress, which was shown to trigger binge eating episodes in BN. Furthermore, difficulties in emotion regulation have been seen to play an important role in the psychopathology of eating disorders, including BN. Seeing that BN is the most prevalent eating disorder in Lebanon, which is linked to the stressful events the country has been through, the study aims to examine the indirect effect of emotional dysregulation on this relationship between mental health issues (stress, anxiety and depression) and bulimia nervosa among young adults. We hypothesize that difficulties in emotion regulation would have an indirect effect in the relationship between mental health and BN.

METHODS

This was a cross-sectional observational study, based on an online anonymous survey, which was carried out between September and December of 2020. Participants were all 18 years and above, recruited from all Lebanese governorates (n = 1175).

RESULTS

Difficulties in emotion regulation mediated the association between anxiety/stress/depression and bulimia. Higher mental health issues were significantly associated with more difficulties in emotion regulation; higher difficulties in emotion regulation were significantly associated with more bulimia. Finally, higher anxiety and higher stress, but not depression, were significantly and directly associated with higher bulimia.

CONCLUSION

Results of this study could be used by mental health professional to shed light on the difficulties in emotion regulation in patients with BN and try to use therapeutic strategies to help them better regulate their emotions.

Prospects for new drugs to treat binge-eating disorder: Insights from psychopathology and neuropharmacology

BACKGROUND

Binge-eating disorder (BED) is a common psychiatric condition with adverse psychological and metabolic consequences. Lisdexamfetamine (LDX) is the only approved BED drug treatment. New drugs to treat BED are urgently needed.

METHODS

A comprehensive review of published psychopathological, pharmacological and clinical findings.

RESULTS

The evidence supports the hypothesis that BED is an impulse control disorder with similarities to ADHD, including responsiveness to catecholaminergic drugs, for example LDX and dasotraline. The target product profile (TPP) of the ideal BED drug combines treating the psychopathological drivers of the disorder with an independent weight-loss effect. Drugs with proven efficacy in BED have a common pharmacology; they potentiate central noradrenergic and dopaminergic neurotransmission. Because of the overlap between pharmacotherapy in attention deficit hyperactivity disorder (ADHD) and BED, drug-candidates from diverse pharmacological classes, which have already failed in ADHD would also be predicted to fail if tested in BED. The failure in BED trials of drugs with diverse pharmacological mechanisms indicates many possible avenues for drug discovery can probably be discounted.

CONCLUSIONS

(1) The efficacy of drugs for BED is dependent on reducing its core psychopathologies of impulsivity, compulsivity and perseveration and by increasing cognitive control of eating. (2) The analysis revealed a large number of pharmacological mechanisms are unlikely to be productive in the search for effective new BED drugs. (3) The most promising areas for new treatments for BED are drugs, which augment noradrenergic and dopaminergic neurotransmission and/or those which are effective in ADHD.

Regional Neural Activity Abnormalities and Whole-Brain Functional Connectivity Reorganization in Bulimia Nervosa: Evidence From Resting-State fMRI

The management of eating behavior in bulimia nervosa (BN) patients is a complex process, and BN involves activity in multiple brain regions that integrate internal and external functional information. This functional information integration occurs in brain regions involved in reward, cognition, attention, memory, emotion, smell, taste, vision and so on. Although it has been reported that resting-state brain activity in BN patients is different from that of healthy controls, the neural mechanisms remain unclear and need to be further explored. The fractional amplitude of low-frequency fluctuation (fALFF) analyses are an important data-driven method that can measure the relative contribution of low-frequency fluctuations within a specific frequency band to the whole detectable frequency range. The fALFF is well suited to reveal the strength of interregional cooperation at the single-voxel level to investigate local neuronal activity power. FC is a brain network analysis method based on the level of correlated dynamics between time series, which establishes the connection between two spatial regions of interest (ROIs) with the assistance of linear temporal correlation. Based on the psychological characteristics of patients with BN and the abnormal brain functional activities revealed by previous neuroimaging studies, in this study, we investigated alterations in regional neural activity by applying fALFF analysis and whole-brain functional connectivity (FC) in patients with BN in the resting state and to explore correlations between brain activities and eating behavior. We found that the left insula and bilateral inferior parietal lobule (IPL), as key nodes in the reorganized resting-state neural network, had altered FC with other brain regions associated with reward, emotion, cognition, memory, smell/taste, and vision-related functional processing, which may have influenced restrained eating behavior. These results could provide a further theoretical basis and potential effective targets for neuropsychological treatment in patients with BN.

Volume and Connectivity Differences in Brain Networks Associated with Cognitive Constructs of Binge Eating

Bulimia nervosa (BN) and binge eating disorder (BED) are characterized by episodes of eating large amounts of food while experiencing a loss of control. Recent studies suggest that the underlying causes of BN/BED consist of a complex system of environmental cues, atypical processing of food stimuli, altered behavioral responding, and structural/functional brain differences compared with healthy controls (HC). In this narrative review, we provide an integrative account of the brain networks associated with the three cognitive constructs most integral to BN and BED, namely increased reward sensitivity, decreased cognitive control, and altered negative affect and stress responding. We show altered activity in BED/BN within several brain networks, specifically in the striatum, insula, prefrontal cortex (PFC) and orbitofrontal cortex (OFC), and cingulate gyrus. Numerous key nodes in these networks also differ in volume and connectivity compared with HC. We provide suggestions for how this integration may guide future research into these brain networks and cognitive constructs.

Dynamic Stress Responses and Real-Time Symptoms in Binge-Eating Disorder

BACKGROUND

Stress is a dynamic construct that predicts a range of health behaviors and conditions, including binge eating and excess weight. Thus far, there have been limited and inconsistent findings regarding stress responses in binge-eating disorder (BED) and insufficient consideration of temporal patterns of stress responses across the weight spectrum.

PURPOSE

The present study used ecological momentary assessment (EMA) to examine stress reactivity (i.e., the magnitude of the initial stress response), recovery (i.e., how long the stress response lasts before returning to baseline), and pileup (i.e., accumulation of repeated experiences of stressors and responses over time) as predictors of binge-eating symptoms (BES) and food craving in BED.

METHODS

Adults with BED (N = 115) completed a 7 day EMA protocol assessing stressful events, perceived stress, binge eating, and food craving prior to being randomized to a behavioral intervention.

RESULTS

Generalized estimating equations indicated that moments of greater stress pileup predicted greater subsequent BES (within-person effect). Participants with higher perceived stress and pileup reported greater overall BES and craving, and those with better recovery reported higher overall craving (between-person effects).

CONCLUSIONS

Findings highlight the importance of considering the dynamic nature of stress responses and, particularly, that the accumulation of stress over the day is an important trigger for BES.

Neurobiological and Psychological Maintenance Mechanisms Associated with Anticipatory Reward in Bulimia Nervosa

The purpose of this investigation is to identify the anticipatory reward mechanisms that maintain binge eating and purging in bulimia nervosa. Emerging data indicate the importance of reward and anticipatory processes as maintenance mechanisms of bulimia nervosa that can be targeted in treatment. The proposed research will identify neurobiological and psychological anticipatory mechanisms of binge eating and purging using functional magnetic resonance imaging (fMRI), and ecological momentary assessment (EMA) in the natural environment. In this investigation, 60 adults (30 with bulimia nervosa and 30 matched comparison participants) will undergo negative and positive mood inductions followed by an fMRI food selection task (and a comparison shopping task) to examine neurobiological and affective responses to food and non-food reward anticipation. Participants with bulimia nervosa will complete two weeks of EMA examining real-time affect changes in relation to the anticipation of binge eating and purging. These methods will facilitate rigorous assessment of the links between neurobiological (fMRI) and naturalistic (EMA) data in anticipatory reward processes. Findings from this investigation will inform the conceptualization and treatment of bulimia nervosa by identifying the role of reward anticipation in symptom maintenance, providing a crucial framework for targeting these anticipatory processes in existing and novel interventions.

Descriptive analysis of binge eating in adult and adolescent females

PURPOSE

Provide qualitative descriptions of context and characteristics of binge eating in adults and adolescents to explore consistency in precipitating factors.

METHOD

Open-ended, qualitative interviews were administered to an adult sample (n = 24) and an adolescent sample (n = 20) to collect details about the context in which two binge episodes occurred.

RESULTS

Factors and context of the binge episodes were similar between adults and adolescents. In contrast, the two binge episodes described by each individual were not consistent. Binge episodes were not strongly affect-driven or food cue-driven.

CONCLUSIONS

Binge eating appears similar between adults and adolescents, which may have treatment implications. Similar treatment approaches may be used with both age groups and would benefit from covering a broad range of binge triggers rather than attempting to match individuals into an approach focused on particular triggers.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

Prefrontal Responses during Proactive and Reactive Inhibition Are Differentially Impacted by Stress in Anorexia and Bulimia Nervosa

Binge eating is a distressing, transdiagnostic eating disorder symptom associated with impulsivity, particularly in negative mood states. Neuroimaging studies of bulimia nervosa (BN) report reduced activity in frontostriatal regions implicated in self-regulatory control, and an influential theory posits that binge eating results from self-regulation failures under stress. However, there is no direct evidence that psychological stress impairs self-regulation in binge-eating disorders, or that any such self-regulatory deficits generalize to binge eating in underweight individuals (i.e., anorexia nervosa bingeing/purging subtype; AN-BP). We therefore determined the effect of acute stress on inhibitory control in 85 women (BN, 33 women; AN-BP, 22 women; 30 control participants). Participants underwent repeated functional MRI scanning during performance of the Stop-signal anticipation task, a validated measure of proactive (i.e., anticipation of stopping) and reactive (outright stopping) inhibition. Neural and behavioral responses to induced stress and a control task were evaluated on 2 consecutive days. Women with BN had reduced proactive inhibition, while prefrontal responses were increased in both AN-BP and BN. Reactive inhibition was neurally and behaviorally intact in both diagnostic groups. Both AN-BP and BN groups showed distinct stress-induced changes in inferior and superior frontal activity during both proactive and reactive inhibition. However, task performance was unaffected by stress. These results offer novel evidence of reduced proactive inhibition in BN, yet inhibitory control deficits did not generalize to AN-BP. Our findings identify intriguing alterations of stress responses and inhibitory function associated with binge eating, but they counsel against stress-induced failures of inhibitory control as a comprehensive explanation for loss-of-control eating.

SIGNIFICANCE STATEMENT Binge eating is a common psychiatric syndrome that feels uncontrollable to the sufferer. Theoretically, it has been related to reduced self-regulation under stress, but there remains no direct evidence for this link in binge-eating disorders. Here, we examined how experimentally induced stress affected response inhibition in control participants and women with anorexia nervosa and bulimia nervosa. Participants underwent repeated brain scanning under stressful and neutral conditions. Although patient groups had intact action cancellation, the slowing of motor responses was impaired in bulimia nervosa, even when the likelihood of having to stop increased. Stress altered brain responses for both forms of inhibition in both groups, yet performance remained unimpaired. These findings counsel against a simple model of stress-induced disinhibition as an adequate explanation for binge eating.

A systematic review of neural correlates of dysregulated eating associated with obesity risk in youth

Dysregulated eating among children and adolescents is associated with a wide range of negative mental and physical health outcomes, including obesity. However, less is known regarding underlying neural mechanisms underlying such behaviors. Therefore, the present manuscript systematically reviewed neuroimaging research examining dysregulated eating behavior linked to excess weight in children and adolescents. A systematic literature search identified 23 eligible studies, the majority of which were cross-sectional functional magnetic resonance imaging (fMRI) studies and excluded participants with psychiatric disorders. Dysregulated eating was captured by measures of eating styles and eating self-regulation, eating disorder behaviors, food addiction, objective measures of non-homeostatic eating and caloric restriction. While preliminary, findings suggested eating dysregulation was related to aberrant functioning within the frontostriatal and frontoparietal regions involved in self-regulatory processes, as well as regions involved in satiety signaling and interoception. This heterogeneous body of research is continually growing and may have potential to inform future prevention and intervention approaches. Results also identified several important limitations to consider and highlight key areas for future research.

Lack of guilt, shame, and remorse following weight stigma expression: a real-time assessment pilot study

Objective

Weight stigma is pervasive and is associated with negative health and psychological outcomes. Few studies have examined weight stigma perpetration or the emotions individuals experience after perpetrating weight stigma. This study used experience sampling to explore the nature and frequency of weight stigma behaviors and cognitions and moral emotions (shame, guilt, remorse, pride) in the perpetrator following weight stigma perpetration.

Methods

Participants were college students (N = 31, 77.1% female). Participants completed baseline measures of anti-fat attitudes and one week of experience sampling phone prompts assessing: (1) weight stigma behaviors and cognitions and (2) moral emotions. Generalized estimating equation analyses were used to model trajectories of moral emotions after weight stigma events.

Results

Thirty-one participants reported 1,008 weight stigma events over 7.5 days. Feelings of guilt, shame, and remorse decreased after weight stigma perpetration. Individuals also reported feeling less proud after engaging in weight stigma.

Conclusions

Weight stigma occurs frequently as reported by perpetrators. A lack of remorse, guilt, and shame is evident in undergraduates after they express weight stigma; however, individuals in this study also reported feeling less pride after perpetration. This study highlights the need for future studies to explore the expression of weight stigma from the perspective of perpetrators instead of targets. Results highlight the pervasiveness and normative nature of weight stigma perpetration in everyday life and the need to better understand the emotional response following weight stigma perpetration as a potential mechanism of its perpetuation.

Breaking It Down: Investigation of Binge Eating Components in Animal Models to Enhance Translation

Binge eating (BE) is a core eating disorder behavior that is present across nearly all eating disorder diagnoses (e. g., bulimia nervosa, binge eating disorder, anorexia nervosa binge/purge subtype), and is also widely present in the general population. Despite the prevalence of BE, limited treatment options exist and there are often high rates of relapse after treatment. There is evidence showing that genetic factors contribute to the heritability of BE and support for biological contributions to BE. However, more work is needed to fully understand neurobiological mechanisms underlying BE. One approach to target this problem is to separate BE into its distinct clinical components that can be more easily modeled using pre-clinical approaches. To date, a variety of animal models for BE have been used in pre-clinical studies; but there have been challenges translating this work to human BE. Here, we review these pre-clinical approaches by breaking them down into three clinically-significant component parts (1) consumption of a large amount of food; (2) food consumption within a short period of time; and (3) loss of control over eating. We propose that this rubric identifies the most frequently used and effective ways to model components of BE behavior using pre-clinical approaches with the strongest clinical relevance. Finally, we discuss how current pre-clinical models have been integrated with techniques using targeted neurobiological approaches and propose ways to improve translation of pre-clinical work to human investigations of BE that could enhance our understanding of BE behavior.

Exploring Neural Mechanisms Related to Cognitive Control, Reward, and Affect in Eating Disorders: A Narrative Review of FMRI Studies

Studies using functional magnetic resonance imaging (fMRI) have contributed to our understanding of possible neural abnormalities among individuals with eating disorders. Many of these studies have focused on three domains: 1) cognitive control, 2) reward processing, and 3) affective processing. This review attempts to summarize the recent fMRI findings across these domains among the most well-characterized eating disorders: anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Though the literature is a bit murky, a few major themes have emerged. Cognitive control systems are affected among individuals across eating disorder diagnoses, but effects seem least pronounced in AN. Specifically, individuals with all eating disorders appear to show decreased prefrontal activation during cognitive control, but there is less evidence in AN linking decreased prefrontal activation with behavior. There is some evidence that the reinforcing value of food is reduced in AN, but individuals with BN and BED show hyperactivation to rewarding food-related stimuli, suggesting the reinforcing value of food may be enhanced. However, more complex reward processing paradigms show that individuals with BN and BED exhibit hypoactivation to reward anticipation and provide mixed results with regards to reward receipt. There are fewer neuroimaging findings related to affective processing, yet behavioral findings suggest affective processing is important in understanding eating disorders. Though the extant literature is complicated, these studies represent a foundation from which to build and provide insight into potential neurobiological mechanisms that may contribute to the pathophysiology of eating disorders.

The role of affect in the maintenance of binge-eating disorder: Evidence from an ecological momentary assessment study

Affect regulation models of eating disorder behavior, which predict worsening of affect prior to binge-eating episodes and improvement in affect following such episodes, have received support in anorexia nervosa and bulimia nervosa. However, limited work has examined the trajectories of affect surrounding binge eating in binge-eating disorder (BED). In the current study, ecological momentary assessment data from 112 men and women with BED were used to examine the trajectories of positive affect (PA), negative affect (NA), guilt, fear, hostility, and sadness relative to binge-eating episodes. Prior to binge episodes, PA significantly decreased, whereas NA and guilt significantly increased. Following binge episodes, levels of NA and guilt significantly decreased and PA stabilized. Overall, results indicate improvements in affect following binge-eating episodes, suggesting that binge eating may function to alleviate unpleasant emotional experiences among individuals with BED, which is consistent with affect regulation models of eating pathology. Because improvements in negative affect were primarily driven by change in guilt, findings also highlight the relative importance of understanding the relationship between guilt and binge-eating behavior within this population. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Neuroendocrinology of reward in anorexia nervosa and bulimia nervosa: Beyond leptin and ghrelin

The pathophysiology of anorexia nervosa (AN) and bulimia nervosa (BN) are still poorly understood, but psychobiological models have proposed a key role for disturbances in the neuroendocrines that signal hunger and satiety and maintain energy homeostasis. Mounting evidence suggests that many neuroendocrines involved in the regulation of homeostasis and body weight also play integral roles in food reward valuation and learning via their interactions with the mesolimbic dopamine system. Neuroimaging data have associated altered brain reward responses in this system with the dietary restriction and binge eating and purging characteristic of AN and BN. Thus, neuroendocrine dysfunction may contribute to or perpetuate eating disorder symptoms via effects on reward circuitry. This narrative review focuses on reward-related neuroendocrines that are altered in eating disorder populations, including peptide YY, insulin, stress and gonadal hormones, and orexins. We provide an overview of the animal and human literature implicating these neuroendocrines in dopaminergic reward processes and discuss their potential relevance to eating disorder symptomatology and treatment.

From Ecological Momentary Assessment (EMA) to Ecological Momentary Intervention (EMI): Past and Future Directions for Ambulatory Assessment and Interventions in Eating Disorders

PURPOSE OF REVIEW

Ambulatory assessment methods, including ecological momentary assessment (EMA), have often been used in eating disorders (EDs) to assess the type, frequency, and temporal sequencing of ED symptoms occurring in naturalistic environments. Relatedly, growing research in EDs has explored the utility of ecological momentary interventions (EMIs) to target ED symptoms. The aims of the present review were to (1) synthesize recent literature pertaining to ambulatory assessment/EMA and EMI in EDs, and (2) identify relevant limitations and future directions in these domains.

RECENT FINDINGS

With respect to ambulatory assessment and EMA, there has been substantial growth in the expansion of constructs assessed with EMA, the exploration of state- vs. trait-level processes, integration of objective and passive assessment approaches, and consideration of methodological issues. The EMI literature in EDs also continues to grow, though most of the recent research focuses on mobile health (mHealth) technologies with relatively minimal EMI components that adapt to momentary contextual information. Despite these encouraging advances, there remain several promising areas of ambulatory assessment research and clinical applications in EDs going forward. These include integration of passive data collection, use of EMA in treatment evaluation and design, evaluation of dynamic system processes, inclusion of diverse samples, and development and evaluation of adaptive, tailored EMIs such as just-in-time adaptive interventions. While much remains to be learned in each of these domains, the continual growth in mobile technology has potential to facilitate and refine our understanding of the nature of ED psychopathology and ultimately improve intervention approaches.

Subcortical Shape Abnormalities in Bulimia Nervosa

BACKGROUND

Bulimia nervosa (BN) is associated with functional abnormalities in frontostriatal and frontolimbic circuits. Although structural alterations in the frontal portions of these circuits have been observed, this is the first study of subcortical surface morphometry and the largest study of subcortical volume in BN.

METHODS

Anatomical magnetic resonance scans were acquired from 62 female participants with full and subthreshold BN (mean age ± SD, 18.7 ± 4.0 years) and 65 group-matched healthy control participants (mean age ± SD, 19.3 ± 5.7 years). General linear models were used to compare groups and assess the significance of group-by-age interactions on the shape and total volume of 15 subcortical structures (p < .05, familywise error corrected). Associations with illness severity and duration were assessed in the BN group.

RESULTS

Subcortical volumes did not differ across groups, but vertexwise analyses revealed inward shape deformations on the anterior surface of the pallidum in BN relative to control participants that were associated with binge-eating frequency and illness duration. Inward deformations on the ventrolateral thalamus and dorsal amygdala were more pronounced with advancing age in the BN group, and inward deformations on the caudate, putamen, and amygdala were associated with self-induced vomiting frequency.

CONCLUSIONS

Our findings point to localized deformations on the surface of subcortical structures in areas that comprise both reward and cognitive control circuits. These deformations were more pronounced among older BN participants and among those with the most severe symptoms. Such precise localization of alterations in subcortical morphometry may ultimately aid in efforts to identify markers of risk and BN persistence.

Stress as a potential moderator of ovarian hormone influences on binge eating in women

Previous research has demonstrated significant associations between increased levels of ovarian hormones and increased rates of binge eating (BE) in women. However, whereas all women experience fluctuations in ovarian hormones across the menstrual cycle, not all women binge eat in response to these fluctuations, suggesting that other factors must contribute. Stress is one potential contributing factor. Specifically, it may be that hormone-BE associations are stronger in women who experience high levels of stress, particularly as stress has been shown to be a precipitant to BE episodes in women. To date, no studies have directly examined stress as a moderator of hormone-BE associations, but indirect data (that is, associations between BE and stress and between ovarian hormones and stress) could provide initial clues about moderating effects. Given the above, the purpose of this narrative review was to evaluate these indirect data and their promise for understanding the role of stress in hormone-BE associations. Studies examining associations between all three phenotypes (that is, ovarian hormones, stress, and BE) in animals and humans were reviewed to provide the most thorough and up-to-date review of the literature on the potential moderating effects of stress on ovarian hormone-BE associations. Overall, current evidence suggests that associations between hormones and BE may be stronger in women with high stress levels, possibly via altered hypothalamic-pituitary-adrenal axis response to stress and increased sensitivity to and altered effects of ovarian hormones during stress. Additional studies are necessary to directly examine stress as a moderator of ovarian hormone-BE associations and identify the mechanisms underlying these effects.

Editorial: Connecting the Nodes of Altered Brain Network Organization in Eating Disorders

Two prevalent eating disorders (ED) in adolescence are anorexia nervosa (AN) and bulimia nervosa (BN). AN is characterized primarily by an extensive restriction of energy intake leading to significantly low body weight. In contrast, the cardinal symptom of BN is uncontrolled eating of an abnormally large amount of food, followed by compensatory behavior to avoid weight gain (eg, self-induced vomiting or laxative abuse). Despite these differences and the fact that individuals with BN are usually of normal weight, patients with both disorders have an abnormal preoccupation with body weight and shape,¹ often in the form of distressing ruminations.^2,3 Left untreated, body image distortion and associated extreme eating/purging habits often have severe and life-long physical, social and psychological consequences. A better understanding of the neurobiological substrates of clinical symptoms may help to improve therapeutic interventions and outcome.⁴.

Affect, reward, and punishment in anorexia nervosa: a narrative overview

INTRODUCTION

Anorexia nervosa (AN) is a serious psychiatric disorder that is difficult to treat and often follows a protracted course. A number of theoretical models have been proposed for the etiology and maintenance of AN. Two domains that have received substantial attention in the literature on AN are affect and reward/punishment processes. However, despite an overlap in the nature and implications of these processes, studies of AN addressing these constructs have typically investigated them independently.

PURPOSE

The purpose of this narrative review is to integrate the literature on the role of affect, reward, and punishment in AN.

METHOD

We provide a focused narrative overview of the literature relating to the affect, reward, and punishment in AN via a synthesis of recent reviews and meta-analyses.

RESULTS

We first describe several prominent affect and reward/punishment-based conceptualizations of AN, followed by a brief overview of the existing empirical literature in these domains.

CONCLUSION

We provide a critical discussion of the disparate nature of these literatures in AN, including associated limitations. We then conclude with an extensive discussion of directions for future research that integrate the study of affect and reward/punishment processes in AN.

LEVEL OF EVIDENCE

Level V, narrative review.

The potential of calibrated fMRI in the understanding of stress in eating disorders

Eating disorders (ED), including Anorexia Nervosa (AN), Bulimia Nervosa (BN), and Binge Eating Disorder (BED), are medically dangerous psychiatric disorders of unknown etiology. Accumulating evidence supports a biopsychosocial model that includes genetic heritability, neurobiological vulnerability, and psychosocial factors, such as stress, in the development and maintenance of ED. Notably, stress hormones influence appetite and eating, and dysfunction of the physiological stress response has been implicated in ED pathophysiology. Stress signals also appear associated with food reward neurocircuitry response in ED, providing a possible mechanism for the role of stress in appetite dysregulation. This paper provides a review of some of the interacting psychological, behavioral, physiological, and neurobiological mechanisms involved in the stress response among individuals with ED, and discusses novel neuroimaging techniques to address potential physiological confounds of studying neural correlates of stress in ED, such as calibrated fMRI.

The impact of neural responses to food cues following stress on trajectories of negative and positive affect and binge eating in daily life

Stress and affect have been implicated in the maintenance of binge eating for women with symptoms of bulimia nervosa (BN). Neuroimaging and ecological momentary assessment (EMA) have separately examined how these variables may contribute to eating disorder behavior. Though both methodologies have their own strengths, it's unclear how either methodology might inform the other. This study examined the impact of individual differences in neural reactivity to food cues following acute stress on the trajectories of positive affect (PA) and negative affect (NA) surrounding binge eating. Women (n = 16) with BN symptoms viewed palatable food cues before and after a stress induction in the scanner. For two weeks, participants responded to prompts assessing affect and binge episodes several times a day. EMA data revealed NA increased and PA decreased before binge episodes in the natural environment. Additionally, NA decreased while PA increased following binge episodes. Changes in activation in the ACC, amygdala, and the vmPFC significantly moderated the relationship of affect to binge eating. However, lateral differences of each brain region uniquely moderator the trajectory of PA, NA, or both to binge eating. Specifically, those with less change in BOLD response reported significantly increasing NA and decreasing PA prior to binges, while women with greater decreases reported no change in affect. Following binge eating, individuals with decreased change in BOLD response reported decreasing NA and increasing PA. This may suggest individual differences in neural response to food cues under stress appear to underlie affect driven theory on the antecedents to binge eating.

Experience sampling methodology in mental health research: new insights and technical developments

In the mental health field, there is a growing awareness that the study of psychiatric symptoms in the context of everyday life, using experience sampling methodology (ESM), may provide a powerful and necessary addition to more conventional research approaches. ESM, a structured self-report diary technique, allows the investigation of experiences within, and in interaction with, the real-world context. This paper provides an overview of how zooming in on the micro-level of experience and behaviour using ESM adds new insights and additional perspectives to standard approaches. More specifically, it discusses how ESM: a) contributes to a deeper understanding of psychopathological phenomena, b) allows to capture variability over time, c) aids in identifying internal and situational determinants of variability in symptomatology, and d) enables a thorough investigation of the interaction between the person and his/her environment and of real-life social interactions. Next to improving assessment of psychopathology and its underlying mechanisms, ESM contributes to advancing and changing clinical practice by allowing a more fine-grained evaluation of treatment effects as well as by providing the opportunity for extending treatment beyond the clinical setting into real life with the development of ecological momentary interventions. Furthermore, this paper provides an overview of the technical details of setting up an ESM study in terms of design, questionnaire development and statistical approaches. Overall, although a number of considerations and challenges remain, ESM offers one of the best opportunities for personalized medicine in psychiatry, from both a research and a clinical perspective.

Associations between cortical thickness, structural connectivity and severity of dimensional bulimia nervosa symptomatology

Bulimia nervosa (BN) is a psychiatric illness defined by preoccupation with body image (cognitive 'symptoms'), binge eating and compensatory behaviors. Although diagnosed BN has been related to grey matter alterations, characterization of brain structure in women with a range of BN symptoms has not been made. This study examined whether cortical thickness (CT) values scaled with severity of BN cognitions in 33 women with variable BN pathology. We then assessed global structural connectivity (SC) of CT to determine if individual differences in global SC relate to BN symptom severity. We used the Eating Disorder Examination Questionnaire (EDE-Q) as a continuous measure of BN symptom severity. EDE-Q score was negatively related to global CT and local CT in the left middle frontal gyrus, right superior frontal gyrus and bilateral orbitofrontal cortex (OFC) and temporoparietal regions. Moreover, cortical thinning was most pronounced in regions with high global connectivity. Finally, individual contributions to global SC at the group level related to EDE-Q score, where increased EDE-Q score correlated with reduced connectivity of the left OFC and middle temporal cortex and increased connectivity of the right superior parietal lobule. Findings represent the first evidence of cortical thinning that relates to cognitive BN symptoms.

Neural Network Alterations Across Eating Disorders: A Narrative Review of fMRI Studies

BACKGROUND

Functional magnetic resonance imaging (fMRI) has provided insight on how neural abnormalities are related to the symptomatology of the eating disorders (EDs): anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). More specifically, an increasingly growing number of brain imaging studies has shed light on how functionally connected brain networks contribute not only to disturbed eating behavior, but also to transdiagnostic alterations in body/interoceptive perception, reward processing and executive functioning.

METHODS

This narrative review aims to summarize recent advances in fMRI studies of patients with EDs by highlighting studies investigating network alterations that are shared across EDs.

RESULTS AND CONCLUSION

Findings on reward processing in both AN and BN patients point to the presence of altered sensitivity to salient food stimuli in striatal regions and to the possibility of hypothalamic inputs being overridden by top-down emotional-cognitive control regions. Additionally, innovative new lines of research suggest that increased activations in fronto-striatal circuits are strongly associated with the maintenance of restrictive eating habits in AN patients. Although significantly fewer studies have been carried out in patients with BN and BED, aberrant neural responses to both food cues and anticipated food receipt appear to occur in these populations. These altered responses, coupled with diminished recruitment of prefrontal cognitive control circuitry, are believed to contribute to the binge eating of palatable foods. Results from functional network connectivity studies are diverse, but findings tend to converge on indicating disrupted resting-state connectivity in executive networks, the default-mode network and the salience network across EDs.

Advancing our understanding of the neurobiology of anorexia nervosa: translation into treatment

A wealth of studies has investigated the neurobiological underpinnings of anorexia nervosa. In our letter to the editor, we point to a number of ways in which the advances in our understanding of the neurobiology of anorexia nervosa - focusing on neuroimaging studies of brain structure and function - can be translated into treatment. We point to how such advances can: inform psychological treatment, be implemented in psychoeducation, point to novel therapeutic targets, lead to the identification of biomarkers, and expand our vocabulary for how we think and talk about anorexia nervosa.