Advances in the neurobiology of eating disorders

Self-Regulation in Eating Behaviors: The Role of Executive Function in Response to Food Stimuli

Human nutrition is characterized by both automatic and self-regulated processes. One of the dimensions that may be employed in monitoring eating behaviors is the cognitive control played by the executive functions (EFs). The role of EFs in affecting eating behaviors has been assessed in empirical studies, but further analyses are needed in a current society characterized by a food-abundant environment. Accordingly, this study attempted to evaluate the association between weight status and executive functions in response to food-related stimuli. One hundred and forty-four young adults took part in the study (25.7% in overweight condition). The participants completed a set of computerized cognitive tasks to assess cognitive and motor inhibition and working memory in two different conditions: (i) classic versions of the tasks and (ii) modified versions with food cues. The results indicate that food stimuli may influence executive performance and that there is an association between food cue-related executive functioning, particularly in the domain of motor inhibition, and working memory. These results suggest that self-regulation in nutrition may involve executive control. Although further studies are needed, this work suggests the importance of a multidimensional perspective in the analysis of eating behaviors and the relevance of EFs in monitoring our approach to food stimuli in an environmental context.

Psychopathological and Neurobiological Overlap Between Anorexia Nervosa and Self-Injurious Behavior: A Narrative Review and Conceptual Hypotheses

Empirical evidence and clinical observations suggest a strong -yet under acknowledged-link between anorexia nervosa (AN) and non-suicidal self-injurious behavior (NSSI). By reviewing the literature on the psychopathology and neurobiology of AN and NSSI, we shed light on their relationship. Both AN and NSSI are characterized by disturbances in affect regulation, dysregulation of the reward circuitry and the opioid system. By formulating a reward-centered hypothesis, we explain the overlap between AN and NSSI. We propose three approaches understanding the relationship between AN and NSSI, which integrate psychopathology and neurobiology from the perspective of self-destructiveness: (1) a nosographical approach, (2) a research domain (RDoC) approach and (3) a network analysis approach. These approaches will enhance our knowledge of the underlying neurobiological substrates and may provide groundwork for the development of new treatment options for disorders of self-destructiveness, like AN and NSSI. In conclusion, we hypothesize that self-destructiveness is a new, DSM-5-transcending concept or psychopathological entity that is reward-driven, and that both AN and NSSI could be conceptualized as disorders of self-destructiveness.

Cultural shifts in the symptoms of Anorexia Nervosa: The case of Orthorexia Nervosa

Orthorexia Nervosa (ON) is a term describing a fixation on food purity, involving ritualized eating patterns and a rigid avoidance of "unhealthy foods." Those self-identified as having ON tend to focus on food composition and feel immense guilt after eating food deemed "unhealthy." Although not formally recognized as a psychiatric disorder by the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), ON has received increasing attention since its identification in 1997. There is ongoing work to establish diagnostic and empirical tools for measuring ON; embedded in this is the question as to whether or not ON is a new eating disorder. In this paper, we argue ON is not a new psychiatric disorder but rather a new cultural manifestation of anorexia nervosa (AN). We begin by providing an overview of historical representations and classification of eating disorders, with a specific focus on AN. This is followed by discussion of the rise in diet culture and healthism since the 19th century. We conclude by examining the diagnostic validity and utility of ON through a discussion of empirical evidence. Classifying ON under the diagnostic umbrella of AN may improve our understanding of factors underlying restrictive eating behaviors.

Central coherence and set-shifting between nonunderweight eating disorders and anorexia nervosa: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis compared previously documented inefficiencies in central coherence and set-shifting between people with nonunderweight eating disorders (bulimia nervosa and binge-eating disorder) and people with anorexia nervosa.

METHOD

We performed random-effects meta-analyses on 16 studies (1,112 participants) for central coherence and 38 studies (3,505 participants) for set-shifting. Random effects meta-regressions were used to test whether the effect sizes for people with nonunderweight eating disorders were significantly different from the effect sizes for people with anorexia nervosa.

RESULTS

People with anorexia nervosa (Hedge's g = -0.53, 95% CIs: -0.80, -0.27, p < .001) and bulimia nervosa (Hedge's g = -0.70, 95% CIs: -1.14, -0.25, p = .002), but not binge-eating disorder, had significantly poorer central coherence than healthy controls. Similarly, people with anorexia nervosa (Hedge's g = -0.38, 95% CIs: -0.50, -0.26, p < .001) and bulimia nervosa (Hedge's g = -0.55, 95% CIs: -0.81, -0.29, p < .001), but not binge-eating disorder, had significantly poorer set-shifting than healthy controls. The effect sizes for people with nonunderweight eating disorders did not significantly differ from those for people with anorexia nervosa.

DISCUSSION

Our meta-analysis was underpowered to make definitive judgments about people with binge-eating disorder. However, we found that people with bulimia nervosa clearly have central coherence and set-shifting inefficiencies which do not significantly differ from those observed in people with anorexia nervosa. Clinically, this suggests that people with bulimia nervosa might benefit from adjunctive approaches to address these inefficiencies, such as cognitive remediation therapy.

Cognitive and emotional regulation in adolescents and young women with eating disorders

BACKGROUND

Eating disorders (EDs) are associated with a reduced ability to regulate emotion and impulses during the life span. Working memory and executive functions (EFs) are cognitive regulatory systems supported by networks involving the pre-frontal cortex. Studies in EDs found impaired functioning in these domains, showing an association between EDs and the reduced ability to control emotions and impulses.

OBJECTIVE

To investigate EF in adolescents and young women with eating disorders (ED) using a quasi-experimental design, focusing on cognitive efficiency, emotional regulation (ER) and behavioural outcomes also taking into account pharmacological treatment and duration of illness.

METHODS

A sample of 151 females belonging to two groups took part in this study. Twenty-six girls and young women (M_age 22;8 years) with ED and 125 typically developed girls and young women (M_age 17;4 years) completed a battery of cognitive tasks (Go-no-go, Stop-signal task, Symmetry span, Reading Span) and the Youth Self-Report and the Difficulties in Emotional Regulation Scale Performance. A series of ANOVA with the Brown-Forsythe test was used to compare the groups.

RESULTS

Participants with ED and controls did not show significant differences in EF tasks, whereas differences between younger and older participants with ED emerged. Moreover, ER difficulties seem to be associated with mainly internalizing problems in EDs. Further analysis on the full ED sample did not reveal any significant differences associated with the disorder persistence. Considering pharmacological treatment effects over cognitive, emotional and behavioural measures emerged.

CONCLUSIONS

The present study documented no specific differences in EF between control and participants with EDs, whereas important differences emerged in ER and behavioural outcomes perception in the clinical sample, together with a partial influence of pharmacological treatment.

LEVEL OF EVIDENCE

No level of evidence.

Neural responses to food stimuli among individuals with eating and weight disorders: a systematic review of event-related potentials

A systematic review was conducted to investigate event-related potentials (ERPs) in response to food and non-food stimuli among individuals with eating and weight disorders. Limiting the search to studies that have analysed ERPs relating to motivated attention and inhibitory control, 19 research papers were extracted from a systematic search in PubMed, Ovid, and Web of Science (2000-2018). An enhanced attentional bias towards food over non-food images (as indexed by P3(00) and LPP amplitudes) was evident for all populations. Individuals with binge eating disorder showed an enhanced attentional response to food cues compared to healthy controls. Inhibitory control-related ERP components (N2(00) and P3a) increased during food-specific no-go trials, but did not differentiate overweight from 'healthy' weight groups. The N2 amplitude to food pictures were positively correlated with caloric intake and food craving among individuals with obesity and binge eating disorder, respectively, while P3(00) was sensitive to hunger levels among overweight and obese females. The heterogeneity of stimuli/paradigms adopted, component timescales extracted, ERPs analysed, and data presented has challenged this review's ability to produce a robust synthesis of results. Some recommendations for future research are discussed.

Literature Review of Cognitive Neuroscience and Anorexia Nervosa

Studies published between the beginning of 2013 and May 2015 on the neuropsychological functioning of patients with anorexia nervosa compared with healthy participants framed in the context of the Research Domain Criteria matrix identifies evidence for functional differences in three domains: Negative Valance Systems-negative attentional biases and lack of neural responsivity to hunger; Cognitive Systems-limited congruence between clinical and cognitive performance, poorer non-verbal than verbal performance, altered attentional styles to disorder related stimuli, perceptual processing impairment in discriminating body images, weaknesses in central coherence, set shifting weaknesses at low weight status, decision-making weaknesses, and greater neural resources required for working memory; Systems for Social Processes-patients appear to have a different attentional response to faces, and perception and understanding of self and others. Hence, there is evidence to suggest that patients with anorexia nervosa have a specific neuropsychological performance style across tasks in three domains of functioning. Some current controversies and areas for future development are identified.

Could training executive function improve treatment outcomes for eating disorders?

Current gold standard treatments for eating disorders (EDs) lack satisfactory efficacy, and traditional psychological treatments do not directly address executive functioning deficits underpinning ED pathology. The goal of this paper is to explore the potential for enhancing ED treatment outcomes by improving executive functioning deficits that have been demonstrated to underlie eating pathology. To achieve our objective, we (1) review existing evidence for executive functioning deficits that underpin EDs and consider the extent to which these deficits could be targeted in neurocognitive training programs, (2) present the evidence for the one ED neurocognitive training program well-studied to date (Cognitive Remediation Therapy), (3) discuss the utility of neurocognitive training programs that have been developed for other psychiatric disorders with similar deficits, and (4) provide suggestions for the future development and research of neurocognitive training programs for EDs. Despite the fact that the body of empirical work on neurocognitive training programs for eating disorders is very small, we conclude that their potential is high given the combined evidence for the role of deficits in executive functioning in EDs, the initial promise of Cognitive Remediation Training, and the success in treating related conditions with neurocognitive training. Based on the evidence to date, it appears that the development and empirical evaluation of neurocognitive training programs for EDs is warranted.

Application of the Research Domain Criteria (RDoC) framework to eating disorders: emerging concepts and research

The Research Domain Criteria (RDoC) project was initiated by the National Institute of Mental Health as a heuristic for addressing the limitations of categorical, symptom-based psychiatric diagnoses. RDoC is conceptualized as a matrix, with the rows representing dimensional constructs or domains implicated in the expression of psychiatric symptoms and the columns representing units of analysis that can be used to assess dimensional constructs (i.e., genes, molecules, cells, circuits, physiology, behavior, and self-reports). Few studies in eating disorders have adopted an RDoC framework, but accumulating data provide support for the relevance of RDoC dimensions to eating disorder symptoms. Herein, we review findings from RDoC-informed studies across the five domains of functioning included in the RDoC matrix-negative valence systems, positive valence systems, cognitive systems, systems for social processes, and arousal and regulatory systems-and describe directions for future research utilizing RDoC to enhance study design and treatment development in eating disorders.

Bacterial ClpB heat-shock protein, an antigen-mimetic of the anorexigenic peptide α-MSH, at the origin of eating disorders

The molecular mechanisms at the origin of eating disorders (EDs), including anorexia nervosa (AN), bulimia and binge-eating disorder (BED), are currently unknown. Previous data indicated that immunoglobulins (Igs) or autoantibodies (auto-Abs) reactive with α-melanocyte-stimulating hormone (α-MSH) are involved in regulation of feeding and emotion; however, the origin of such auto-Abs is unknown. Here, using proteomics, we identified ClpB heat-shock disaggregation chaperone protein of commensal gut bacteria Escherichia coli as a conformational antigen mimetic of α-MSH. We show that ClpB-immunized mice produce anti-ClpB IgG crossreactive with α-MSH, influencing food intake, body weight, anxiety and melanocortin receptor 4 signaling. Furthermore, chronic intragastric delivery of E. coli in mice decreased food intake and stimulated formation of ClpB- and α-MSH-reactive antibodies, while ClpB-deficient E. coli did not affect food intake or antibody levels. Finally, we show that plasma levels of anti-ClpB IgG crossreactive with α-MSH are increased in patients with AN, bulimia and BED, and that the ED Inventory-2 scores in ED patients correlate with anti-ClpB IgG and IgM, which is similar to our previous findings for α-MSH auto-Abs. In conclusion, this work shows that the bacterial ClpB protein, which is present in several commensal and pathogenic microorganisms, can be responsible for the production of auto-Abs crossreactive with α-MSH, associated with altered feeding and emotion in humans with ED. Our data suggest that ClpB-expressing gut microorganisms might be involved in the etiology of EDs.

Pediatric feeding and eating disorders: current state of diagnosis and treatment

The Diagnostic and Statistical Manual of Mental Disorders now recognizes six primary feeding and eating disorders including pica, rumination disorder, avoidant/restrictive food intake disorder, anorexia nervosa, bulimia nervosa and binge-eating disorder. Guided by research from the past 3 years, the current review outlines diagnostic criteria for each disorder, their clinical correlates and treatment options. Recent modifications to diagnostic criteria will likely help to improve treatment outcomes and prognosis. Nevertheless, several concerns remain regarding the validity of current diagnostic criteria for youth, including the clinical relevance of the size and frequency of binge eating episodes. Additionally, the lack of randomized controlled trials has led to an overreliance on data from quasi-experimental studies, case series and single case studies that impede development of strong clinical recommendations for treating feeding and eating disorders. Recommendations for future research include identifying empirically supported treatments and prevention programs focused on early markers of pediatric feeding and eating concerns.

Ovarian Hormone Influences on Dysregulated Eating: A Comparison of Associations in Women with versus without Binge Episodes

Changes in ovarian hormones predict changes in emotional eating across the menstrual cycle. However, prior studies have not examined whether the nature of associations varies across dysregulated eating severity. The current study determined whether the strength and/or nature of hormone/dysregulated eating associations differ based on the presence of clinically diagnosed binge episodes (BEs). Participants included 28 women with BEs and 417 women without BEs who provided salivary hormone samples, ratings of emotional eating, and BE frequency for 45 days. Results revealed stronger associations between dysregulated eating and ovarian hormones in women with BEs as compared to women without BEs. The nature of associations also differed, as progesterone moderated the effects of lower estradiol levels on dysregulated eating in women with BEs only. Although hormone/dysregulated eating associations are present across the spectrum of pathology, the nature of associations may vary in ways that have implications for etiological models and treatment.