New insights into symptoms and neurocircuit function of anorexia nervosa

Eating disorders, gene-environment interactions and epigenetics

This review describes the various subtypes of eating disorders and examines factors associated with the risk of illness. It considers evidence that the development and maintenance of eating disorders is due to gene-environment interactions (GxE) that alter genetic expression via epigenetic processes. It describes how environmental factors such as those associated with nutrition and/or stress may cause epigenetic changes which have transcriptional and phenotypic effects, which, in turn, alter the long term risk of developing an eating disorder. It reviews theoretical and practical issues associated with epigenetic studies in psychiatry and how these are relevant to eating disorders. It examines the limited number of epigenetic studies which have been conducted in eating disorders and suggests directions for further research. Understanding the relationship between epigenetic processes and the risk of an eating disorder opens possibilities for preventive and/or therapeutic interventions. For example, epigenetic changes associated with diet and weight may be reversible and those associated with cognitive processes may be accessible to pharmacological interventions.

The tempted brain eats: pleasure and desire circuits in obesity and eating disorders

What we eat, when and how much, all are influenced by brain reward mechanisms that generate "liking" and "wanting" for foods. As a corollary, dysfunction in reward circuits might contribute to the recent rise of obesity and eating disorders. Here we assess brain mechanisms known to generate "liking" and "wanting" for foods and evaluate their interaction with regulatory mechanisms of hunger and satiety, relevant to clinical issues. "Liking" mechanisms include hedonic circuits that connect together cubic-millimeter hotspots in forebrain limbic structures such as nucleus accumbens and ventral pallidum (where opioid/endocannabinoid/orexin signals can amplify sensory pleasure). "Wanting" mechanisms include larger opioid networks in nucleus accumbens, striatum, and amygdala that extend beyond the hedonic hotspots, as well as mesolimbic dopamine systems, and corticolimbic glutamate signals that interact with those systems. We focus on ways in which these brain reward circuits might participate in obesity or in eating disorders.

Eating disorders

This Seminar adds to the previous Lancet Seminar about eating disorders, published in 2003, with an emphasis on the biological contributions to illness onset and maintenance. The diagnostic criteria are in the process of review, and the probable four new categories are: anorexia nervosa, bulimia nervosa, binge eating disorder, and eating disorder not otherwise specified. These categories will also be broader than they were previously, which will affect the population prevalence; the present lifetime prevalence of all eating disorders is about 5%. Eating disorders can be associated with profound and protracted physical and psychosocial morbidity. The causal factors underpinning eating disorders have been clarified by understanding about the central control of appetite. Cultural, social, and interpersonal elements can trigger onset, and changes in neural networks can sustain the illness. Overall, apart from studies reporting pharmacological treatments for binge eating disorder, advances in treatment for adults have been scarce, other than interest in new forms of treatment delivery.

Reward and the serotonergic system

Anhedonia, as a failure to experience rewarding stimuli, is a key characteristic of many psychiatric disorders including depression and schizophrenia. Investigations on the neurobiological correlates of reward and hedonia/anhedonia have been a growing subject of research demonstrating several neuromodulators to mediate different aspects of reward processing. Whereas the majority of research on reward mainly focused on the dopamine and opioid systems, a serotonergic mechanism has been neglected. However, recent promising results strengthen the pivotal role of serotonin in reward processing. Evidence includes electrophysical and pharmacological as well as genetic and imaging studies. Primate research using single-unit recording of neurons within the dorsal raphe nucleus argues for a serotonergic mediation of reward value, whereas studies using intracranial self-stimulation point to an important contribution of serotonin in modulating motivational aspects of rewarding brain stimulation. Pharmacological studies using agonists and antagonists of serotonergic receptor subtypes and approaches investigating an increase or decrease of the extracellular level of serotonin offer strong evidence for a serotonergic mediation, ranging from aversion to pleasure. This review provides an argument for serotonin as a fundamental mediator of emotional, motivational and cognitive aspects of reward representation, which makes it possibly as important as dopamine for reward processing.

New frontiers in endocrinology of eating disorders

Alterations of both central and peripheral feeding regulatory substances occur in the acute phases of anorexia nervosa (AN) and bulimia nervosa (BN) and, generally, reverse after recovery. Some of these alterations are believed not only to sustain the altered eating behavior but also to contribute to certain psychopathological aspects and/or etiopathogenetic processes of eating disorders (EDs). It has been suggested that EDs are clinical conditions linked to reward-related mechanisms leading to a kind of addiction to self-starvation and/or overeating. Most of the feeding regulatory substances, which are dysregulated in EDs, are also implicated in the modulation of reward, emotional, and cognitive functions, thus representing possible links between altered nutritional regulation, motivated behaviors and reward processes. In this chapter, the ED literature dealing with ghrelin, brain-derived neurotrophic factor, opioid peptides, and endocannabinoids, which have prominent effects on eating behavior, body weight, reward, emotional, and cognitive functions, is reviewed in view of the above suggested links. Moreover, the potential therapeutics of new medications developed on the basis of neuroendocrine aberrations found in EDs is also presented.

Childhood anxiety associated with low BMI in women with anorexia nervosa

OBJECTIVE

Extremely low body mass index (BMI) values are associated with increased risk for death and poor long-term prognosis in individuals with anorexia nervosa (AN). The present study explores childhood personality characteristics that could be associated with the ability to attain an extremely low BMI.

METHODS

Participants were 326 women from the Genetics of Anorexia Nervosa (GAN) Study who completed the Structured Interview for Anorexia Nervosa and Bulimic Syndromes and whose mother completed the Child Behavioral Checklist and/or Revised Dimensions of Temperament Survey.

RESULTS

Children who were described as having greater fear or anxiety by their mothers attained lower BMIs during AN (p < 0.02). Path analysis in the GAN and a validation sample, Price Foundation Anorexia Nervosa Trios Study, confirmed the relation between early childhood anxiety, caloric restriction, qualitative food item restriction, excessive exercise, and low BMI. Path analysis also confirmed a relation between childhood anxiety and caloric restriction, which mediated the relation between childhood anxiety and low BMI in the GAN sample only.

CONCLUSION

Fearful or anxious behavior as a child was associated with the attainment of low BMI in AN and childhood anxiety was associated with caloric restriction. Measures of anxiety and factors associated with anxiety-proneness in childhood may index children at risk for restrictive behaviors and extremely low BMIs in AN.

Cognitive remediation therapy for eating disorders: development, refinement and future directions

In this chapter, we aim to address some basic conceptual and practical questions about cognitive remediation therapy (CRT) for eating disorders. We begin by providing an overall historical, conceptual, and theoretical framework for CRT. Next, we discuss the specific indications for how and why CRT might be useful for eating disorders based on existing neuropsychological research evidence. We also provide an overview of the types of tasks and stimuli used in CRT and a general protocol for a manualized version of CRT. In addition, modifications of the adult CRT manual for use with adolescents as well as preliminary acceptability of the approach with this younger age group are described. We also propose various ways to integrate CRT in a variety of inpatient and outpatient programmes. Finally, a discussion of potential future directions in research using the tools of neurocognitive assessment, imaging and treatment research is provided.

Genetic findings in anorexia and bulimia nervosa

Anorexia nervosa (AN) and bulimia nervosa (BN) are complex disorders associated with disordered eating behavior. Heritability estimates derived from twin and family studies are high, so that substantial genetic influences on the etiology can be assumed for both. As the monoaminergic neurotransmitter systems are involved in eating disorders (EDs), candidate gene studies have centered on related genes; additionally, genes relevant for body weight regulation have been considered as candidates. Unfortunately, this approach has yielded very few positive results; confirmed associations or findings substantiated in meta-analyses are scant. None of these associations can be considered unequivocally validated. Systematic genome-wide approaches have been performed to identify genes with no a priori evidence for their relevance in EDs. Family-based scans revealed linkage peaks in single chromosomal regions for AN and BN. Analyses of candidate genes in one of these regions led to the identification of genetic variants associated with AN. Currently, an international consortium is conducting a genome-wide association study for AN, which will hopefully lead to the identification of the first genome-wide significant markers.

Cognitive-behavioral flexibility in anorexia nervosa

Anorexia nervosa (AN) patients are characterized by perfectionism and obsessional personality traits. This anorectic personality type is associated with an exaggerated cognitive control and impaired cognitive-behavioral flexibility. Neuropsychological studies addressing flexibility have supported an impaired cognitive set-shifting (i.e., concrete and rigid behaviors to changing rules) as well as an impaired behavioral response shifting (i.e., stereotyped or perseverative behaviors) in AN patients independent of nutritional status and body weight. Furthermore, impaired set-shifting was found in healthy sisters of AN patients suggesting that cognitive inflexibility is a trait marker in AN patients. Brain imaging studies have provided new insights in striatocortical circuit dysfunctions that may underlie both the clinical symptoms of obsessive-compulsive personality traits and the neuropsychological observations of impaired cognitive-behavioral flexibility. The conceptualization of AN as a neurodevelopmental striatocortical disorder may help to develop new promising treatment approaches for this severe disorder.

Neuroanthropology: evolution and emotional embodiment

The Decade of the Mind is a proposal for a research initiative focused on four areas of neuroscience, including mental health, high-level cognitive function, education, and computational applications. Organizing efforts to date have primarily included cognitive scientists, computer scientists, and engineers, as well as physicians. At the same time anthropologists have started to explore the implications of neuroscience for understanding culture. Here we suggest that evolutionary neuroscience can be used to bridge knowledge obtained by social scientists with that obtained in the neurosciences for a more complete appreciation of the mind. We consider such a perspective as neuroanthropology. We use embodiment, an anthropological concept that has been substantiated by recent findings in neuroscience, to illustrate an integrative biocultural approach within neuroanthropology and suggest future possible directions for research.