How extreme dieting becomes compulsive: A novel hypothesis for the role of anxiety in the development and maintenance of anorexia nervosa

Longitudinal changes in neural responses to fearful faces in adolescents with anorexia nervosa - A fMRI study

OBJECTIVE

Although proven neuronal changes are correlated with anorexia nervosa (AN), where these changes occur and how they change during the course of this disease are often unclear; this is especially true regarding emotion processing, e.g., of anxiety, despite a growing body of literature on its importance for the pathophysiology and clinical course of patients with AN.

METHODS

Twenty-two female adolescent patients with AN were scanned during acute starvation and after short-term weight recovery and were compared to 27 healthy controls. A well-established face-matching paradigm involving individuals with different emotions was used during fMRI.

RESULTS

Patients with AN selectively showed significantly increasing neural activation in the somatomotor cortex when viewing fearful faces following short-term weight recovery. No differences were found compared to healthy controls or for neutral, angry or surprised faces. Neural activation in response to fearful faces during acute starvation was associated with lower BMI-SDS and greater illness burden.

CONCLUSION

Higher somatomotor activity could represent anxiety-induced preparations for motor reactions (e.g., fight or flight) that are more pronounced in more affected patients. These results align with recent models of AN that increasingly incorporate anxiety into the pathophysiological and prognostic model of AN and help elucidate its underlying neurological mechanisms.

Examining anxious temperament in anorexia nervosa: Behavioural inhibition and intolerance of uncertainty and their contribution to trait anxiety in adolescents with anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is a serious and complex psychiatric disorder yet treatment results are suboptimal. Insight into the etiology of this illness is much needed. Research highlights the implication of anxiety-related traits in the development and maintenance of AN. This study investigates firstly, behavioural inhibition and intolerance for uncertainty (IU) in adolescents with and without AN, and secondly relations between these traits.

METHODS

In a cross-sectional study, 165 adolescent girls (AN = 94, HC = 71) completed questionnaires measuring behavioural inhibition, IU and trait anxiety. ANOVAs tested differences between AN and HC groups, and mediation models with IU as a mediator between behavioural inhibition and trait anxiety were run.

RESULTS

AN adolescents reported significantly higher levels of behavioural inhibition, IU and trait anxiety compared to their peers. In both AN and HC, a direct and a total effect of behavioural inhibition on trait anxiety was found. However, only in the AN group IU partially mediated the relation between behavioural inhibition and trait anxiety.

LIMITATIONS

Data is cross-sectional and longitudinal studies are required. A mean illness duration of nearly 2 years may mean early effects of malnourishment and habituation and future studies should include patients with shorter illness duration.

CONCLUSIONS

Results highlight that behavioural inhibition and IU may contribute to anxiety in AN whilst their peers may have developed better executive and social-emotional skills to manage uncertainty. Adolescents with AN may benefit from interventions targeting behavioural inhibition and IU.

Habits and Persistent Food Restriction in Patients with Anorexia Nervosa: A Scoping Review

The aetiology of anorexia nervosa (AN) presents a puzzle for researchers. Recent research has sought to understand the behavioural and neural mechanisms of these patients' persistent choice of calorie restriction. This scoping review aims to map the literature on the contribution of habit-based learning to food restriction in AN. PRISMA-ScR guidelines were adopted. The search strategy was applied to seven databases and to grey literature. A total of 35 studies were included in this review. The results indicate that the habit-based learning model has gained substantial attention in current research, employing neuroimaging methods, scales, and behavioural techniques. Food choices were strongly associated with dorsal striatum activity, and habitual food restriction based on the self-report restriction index was associated with clinical impairment in people chronically ill with restricting AN. High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and Regulating Emotions and Changing Habits (REaCH) have emerged as potential treatments. Future research should employ longitudinal studies to investigate the time required for habit-based learning and analyse how developmental status, such as adolescence, influences the role of habits in the progression and severity of diet-related illnesses. Ultimately, seeking effective strategies to modify persistent dietary restrictions controlled by habits remains essential.

The absence of association between anorexia nervosa and smoking: converging evidence across two studies

Previous studies have found increased smoking prevalence amongst adults with anorexia nervosa (AN) compared to the general population. The current investigation explored bidirectional associations between AN and smoking behaviour (initiation and heaviness), to address questions surrounding causation. In Study One, logistic regression models with variance robust standard errors assessed longitudinal associations between AN and smoking, using data from adolescent participants of the Avon Longitudinal Study of Parents and Children (N = 5100). In Study Two, two-sample Mendelian randomisation (MR) tested possible causal effects using summary statistics from publicly available genome-wide association studies (GWAS). Study One provided no clear evidence for a predictive effect of AN on subsequent smoking behaviour, or for smoking heaviness/initiation predicting later AN. MR findings did not support causal effects between AN and smoking behaviour, in either direction. Findings do not support predictive or causal effects between AN and smoking behaviour. Previously reported associations may have been vulnerable to confounding, highlighting the possibility of smoking and AN sharing causal risk factors.

Transdiagnostic fears and avoidance behaviors in self-reported eating disorders

BACKGROUND

Fears and avoidance behaviors are common symptoms of eating disorders. It was investigated whether different eating disorder diagnoses are equally characterized by similar fears and avoidance behaviors.

METHODS

Individuals with self-reported eating disorders (n = 250) and healthy controls (n = 95) completed online questionnaires assessing general fears, eating related fears, and avoidance behaviors.

RESULTS

All self-reported eating disorder diagnoses showed more eating related fears, general fears, and avoidance behaviors than healthy controls. Individuals with binge eating disorder showed less specific and general fears on some but by no means all scales, yet they showed less food avoidance behaviors than all other eating disorders and less eating restraint than anorexia nervosa and bulimia nervosa.

CONCLUSIONS

Eating related fears, general fears, and food avoidance behaviors were found to be transdiagnostic symptoms in self-reported eating disorders. Individuals with binge eating disorder also exhibit more fears and avoidance behaviors than healthy controls, but to a lesser extent than the other eating disorders. Specialized interventions targeting fears and avoidance may be promising add-on interventions not only in the treatment of anorexia nervosa, but in the treatment of all eating disorders.

Food Restriction in Anorexia Nervosa in the Light of Modern Learning Theory: A Narrative Review

Improvements in the clinical management of anorexia nervosa (AN) are urgently needed. To do so, the search for innovative approaches continues at laboratory and clinical levels to translate new findings into more effective treatments. In this sense, modern learning theory provides a unifying framework that connects concepts, methodologies and data from preclinical and clinical research to inspire novel interventions in the field of psychopathology in general, and of disordered eating in particular. Indeed, learning is thought to be a crucial factor in the development/regulation of normal and pathological eating behaviour. Thus, the present review not only tries to provide a comprehensive overview of modern learning research in the field of AN, but also follows a transdiagnostic perspective to offer testable explanations for the origin and maintenance of pathological food rejection. This narrative review was informed by a systematic search of research papers in the electronic databases PsycInfo, Scopus and Web of Science following PRISMA methodology. By considering the number and type of associations (Pavlovian, goal-directed or habitual) and the affective nature of conditioning processes (appetitive versus aversive), this approach can explain many features of AN, including why some patients restrict food intake to the point of life-threatening starvation and others restrict calorie intake to lose weight and binge on a regular basis. Nonetheless, it is striking how little impact modern learning theory has had on the current AN research agenda and practice.

Fear and food: Anxiety-like behavior and the susceptibility to weight loss in an activity-based anorexia rat model

Anorexia nervosa (AN) is a severe psychiatric disorder characterized by energy restriction, low body weight, a fear of gaining weight, and often excessive physical activity. Anxiety disorders appear to constitute a major risk factor for developing AN and are the most frequent comorbidity. Here, the influence of anxiety-like behavior prior to food restriction on increased physical activity, leading to greater susceptibility to weight loss, was tested in rats. Furthermore, the possible anxiolytic effect of starvation itself was analyzed. A chronic starvation model activity-based anorexia (ABA) was applied to mimic physiological and behavioral characteristics of AN. During the induction of starvation and acute starvation, food intake was reduced by 70% and the rats lost 25% of their body weight, which was kept stable to imitate chronic starvation. Anxiety-like behavior was quantified before and after chronic starvation using the elevated plus maze, based on rodents' aversion to open spaces. Anxiety-related behavior before food restriction was associated with increased running-wheel activity during habituation and during the induction of starvation, and predicted faster weight loss in ABA rats. Additionally, food-restricted animals showed less anxiety-like behavior after chronic starvation. Animals showing more anxiety-like behavior appear to be more susceptible to weight loss, partially mediated by increased physical activity. Anxiety-related behavior was associated with increased physical activity, which in turn was associated with more rapid weight loss. Our data let us assume that food restriction has an anxiolytic effect. These findings demonstrate the importance of considering anxiety disorders in patients with AN.

Associations between mealtime anxiety and food intake in anorexia nervosa

OBJECTIVE

A salient disturbance in anorexia nervosa (AN) is the persistent restriction of food intake. Eating behavior in AN is thought to be influenced by anxiety. The current study probed associations between mealtime anxiety and food intake among individuals with AN and healthy comparison individuals (HC).

METHOD

Data were combined across three studies (total of 92 AN and 78 HC) for secondary data analysis. Participants completed a multiitem laboratory buffet meal and visual analogue scale assessments of pre-meal and post-meal anxiety. Linear regression models assessed the association between mealtime anxiety and calorie and fat intake at the meal, and whether associations differed by diagnostic group.

RESULTS

Among individuals with AN, pre-meal anxiety was significantly associated with reduced calorie intake and reduced consumption of calories from fat at the meal; these associations were not observed among HC. There was no evidence for an association between calorie/fat intake at the meal and post-meal anxiety in either group.

DISCUSSION

Treatments that target mealtime anxiety may improve eating and nourishment among individuals with AN. Interventions like exposure therapy that provide skills in overcoming mealtime anxiety might be enhanced by informing patients that post-meal anxiety is not related to intake.

Avoidance in Anorexia Nervosa: Towards a research agenda

Anorexia Nervosa is a severe and disabling mental disorder and a huge challenge to treat. Intense fears of e.g., food, eating, weight gain and social evaluation are core features of anorexia nervosa and obstacles during treatment. The perceived threats trigger avoidance and safety behaviors like highly restrictive eating, strict eating rules, vomiting and body checking, to minimize feared outcomes. The role of avoidance in anorexia nervosa is however hardly studied experimentally. In the present article, the focus is on a new transdiagnostic research agenda featuring both basic and clinical experimental research into avoidance as a most important mechanism maintaining the eating disorder. Avoidance learning and the generalization of learned avoidance behaviors are discussed, as well as safety behaviors and the need for inhibitory learning as a treatment target during exposure therapy.

Motivation to recover for adolescent and adult eating disorder patients in residential treatment

OBJECTIVE

This study aimed to assess how baseline motivation to recover impacts eating disorder (ED) and comorbid symptoms at end-of-treatment (EOT) for adolescents and adults in inpatient/residential treatment.

METHOD

Two hundred and three adolescent (M = 15.90) and 395 adult (M = 25.45) patients with a Diagnostic Statistical Manual, 5th edition ED diagnosis completed the Decisional Balance Scale (DBS) at baseline, and psychosocial measures (ED symptoms, anxiety, depression, obsessive-compulsive disorder symptoms), and %body mass index (kg/m² ; BMI) or median %BMI (for adolescents) at baseline and EOT.

RESULTS

The DBS Avoidance Coping and Burdens subscales at baseline were significantly lower for adolescents than adults (p < 0.001), whereas the DBS Benefits subscale at baseline did not significantly differ between subsamples (p = 0.06). Motivation to recover via DBS subscales was a more reliable predictor of EOT outcomes for both ED and comorbid psychopathology in adults (significant predictor in 19 of 54 total analyses, and 4 significant associations post-Bonferroni correction) than adolescents (significant predictor in 5 of 54 total analyses, and 1 significant association post-Bonferroni correction).

CONCLUSIONS

Baseline motivation to recover may be an important predictor of outcome for adult patients in inpatient/residential treatment but does not appear associated with outcomes for adolescent patients.

Prevention of diet restriction induced hyperactivity but not body-weight reduction in rats co-treated with tryptophan: relationship with striatal serotonin and dopamine metabolism and serotonin-1A auto-receptor expression

Anorexia Nervosa (AN) is an eating and behavioral disorder characterized with anxiety/depression, hyperactivity, behavioral impulsivity and psychosis. Most of the associated symptoms are related to the deficiency of serotonin (5-hydroxytryptamine: 5-HT) stores. A deficiency of 5-HT can modulate dopamine neurotransmission in the striatum to elicit hyperactivity and psychosis in AN patients. Also, the release and availability of 5-HT are modulated by serotonin-1A (5-HT1A) auto-receptor. The present study investigates the role of striatal metabolism of 5-HT and dopamine in precipitating hyperactivity in the rat model of diet restriction (DR) induced AN. The role of tryptophan (Trp) in influencing the 5-HT metabolism and the mRNA expression of 5-HT1A auto-receptor is also investigated. We find that long-term DR for 38 days reduces body-weight in rats and produces hyperactivity, similar to AN. This hyperactivity is characterized by declined striatal metabolism of both, dopamine and 5-HT. The mRNA expression of 5-HT1A auto-receptor in the raphe nuclei is also decreased. Trp co-treatment improves these deficiencies in monoamine metabolism and alleviates hyperactivity. Interestingly, DR-induced changes in body-weights are not effected by Trp co-treatment. The study suggests that the striatal metabolism of 5-HT and dopamine and mRNA expression of 5-HT1A auto-receptor has an important role in the pathogenesis of AN. The finding suggests that co-use of Trp can prevent precipitation of AN by normalizing 5-HT metabolism.

Activity-Based Anorexia Dynamically Dysregulates the Glutamatergic Synapse in the Nucleus Accumbens of Female Adolescent Rats

Intense physical activity and dieting are core symptoms of anorexia nervosa (AN). Their combination evolves into compulsivity, leading the patient into an out-of-control spiral. AN patients exhibit an altered activation of nucleus accumbens (NAc), revealing a dysfunctional mesocorticolimbic reward circuitry in AN. Since evidence exists that a dysregulation of the glutamate system in the NAc influences reward and taking advantage of the activity-based anorexia (ABA) rat model, which closely mimics the hallmarks of AN, we investigated the involvement of the glutamatergic signaling in the NAc in this experimental model. We here demonstrate that food restriction causes hyperactive and compulsive behavior in rodents, inducing an escalation of physical activity, which results in dramatic weight loss. Analysis of the glutamate system revealed that, in the acute phase of the pathology, ABA rats increased the membrane expression of GluA1 AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor subunits together with its scaffolding protein SAP97. Recovery of body weight reduced GluN2A/2B balance together with the expression of their specific scaffolding proteins, thus suggesting persistent maladaptive neurotransmission. Taken together, AMPA and NMDA (N-methyl-D-aspartate) receptor subunit reorganization may play a role in the motivational mechanisms underlying AN.

Binge Eating and Addictive-Like Behaviours in Males and Females

INTRODUCTION

Binge eating is a common behaviour that is strongly linked to both obesity and eating disorder. There is evidence that binge eating commonly co-occurs with other problematic and addictive-like behaviours; however, this has not been explored systematically. The present study aimed to examine the relationship between binge eating, body weight, disordered eating behaviours and associated addictive-like behaviours, with particular attention paid to gender differences.

METHOD

A community sample (N = 500; 75% female, M_age = 32.5 years) reported disordered eating behaviours (i.e. binge eating, purging, restriction of eating, compulsive exercise), body mass index (BMI), food addiction, starvation addiction, exercise dependence, tobacco use and alcohol consumption.

RESULTS

42% of females and 21% of males reported binge eating during the past four weeks. Binge eating was significantly associated with all investigated behaviours in females, and with purging, compulsive exercise and overweight/obesity in males. Controlling for BMI, self-starvation predicted binge eating in males (OR = 1.07), while food addiction (OR = 1.73) and alcohol dependence (OR = 1.11) predicted binge eating in females.

CONCLUSIONS

The multiple associations between binge eating and addictive-like behaviors supports broad screening and generalized prevention efforts. Prevention efforts should reflect gender differences.

Understanding the nature of association between anxiety phenotypes and anorexia nervosa: a triangulation approach

BACKGROUND

Evidence from observational studies suggests an association between anxiety disorders and anorexia nervosa (AN), but causal inference is complicated by the potential for confounding in these studies. We triangulate evidence across a longitudinal study and a Mendelian randomization (MR) study, to evaluate whether there is support for anxiety disorder phenotypes exerting a causal effect on AN risk.

METHODS

Study One assessed longitudinal associations of childhood worry and anxiety disorders with lifetime AN in the Avon Longitudinal Study of Parents and Children cohort. Study Two used two-sample MR to evaluate: causal effects of worry, and genetic liability to anxiety disorders, on AN risk; causal effects of genetic liability to AN on anxiety outcomes; and the causal influence of worry on anxiety disorder development. The independence of effects of worry, relative to depressed affect, on AN and anxiety disorder outcomes, was explored using multivariable MR. Analyses were completed using summary statistics from recent genome-wide association studies.

RESULTS

Study One did not support an association between worry and subsequent AN, but there was strong evidence for anxiety disorders predicting increased risk of AN. Study Two outcomes supported worry causally increasing AN risk, but did not support a causal effect of anxiety disorders on AN development, or of AN on anxiety disorders/worry. Findings also indicated that worry causally influences anxiety disorder development. Multivariable analysis estimates suggested the influence of worry on both AN and anxiety disorders was independent of depressed affect.

CONCLUSIONS

Overall our results provide mixed evidence regarding the causal role of anxiety exposures in AN aetiology. The inconsistency between outcomes of Studies One and Two may be explained by limitations surrounding worry assessment in Study One, confounding of the anxiety disorder and AN association in observational research, and low power in MR analyses probing causal effects of genetic liability to anxiety disorders. The evidence for worry acting as a causal risk factor for anxiety disorders and AN supports targeting worry for prevention of both outcomes. Further research should clarify how a tendency to worry translates into AN risk, and whether anxiety disorder pathology exerts any causal effect on AN.

Predicting the restrictive eating, exercise, and weight monitoring compulsions of anorexia nervosa

PURPOSE

Compulsions surrounding restrictive eating, exercise, and weight monitoring are thought to maintain abnormal eating behaviour in individuals with anorexia nervosa (AN). This study aimed to determine if AN psychopathology and trait anxiety explain the presence of restrictive eating, exercise, and weight monitoring compulsions in a mixed sample.

METHODS

Participants were 31 females with AN and 31 age and gender-matched healthy individuals (HC). Restrictive eating, exercise and weight monitoring compulsion presence was compared between AN and HC groups. Multivariable poisson regression analyses, adjusted for diagnostic status, were conducted to assess the association of both AN psychopathology and trait anxiety with compulsions across the mixed group.

RESULTS

Individuals with AN endorsed a greater number of restrictive eating, exercise and weight monitoring compulsions compared to HC. In adjusted poisson regression analyses neither AN psychopathology nor trait anxiety predicted compulsion presence: incidence rate ratio (IRR) for AN psychopathology = 1.15 [95% CI 0.84, 1.57], p = 0.39; IRR for trait anxiety = 1.01 [95% CI 0.97, 1.06], p = 0.50.

CONCLUSIONS

Greater presence of restrictive eating, exercise and weight monitoring compulsions was reported by individuals with AN, supporting the conceptualisation of disorder behaviours as compulsive. The study was underpowered to robustly evaluate the association between predictors of interest and the compulsions outcome, largely owing to the small sample size. Further investigation is required, ideally using methods able to identify causal and mediation effects.

LEVEL OF EVIDENCE

Level V, cross-sectional study.

Toward A Greater Understanding of the Ways Family-Based Treatment Addresses the Full Range of Psychopathology of Adolescent Anorexia Nervosa

Family-based treatment (FBT) for anorexia nervosa (AN) is an empirically supported treatment for this disorder. Derived from several different schools of family therapy, it is a highly focused approach that initially targets weight restoration under parental management at home. However, the view that manualized FBT is solely a behavioral therapy directing parents to refeed their children AN with the single purpose of weight gain is a common but misleading over simplification of the therapy. Indeed, weight restoration is the main goal only in phase 1 of this 3-phase treatment. When practiced with fidelity and skill, FBT's broadest aim is to promote adolescent development without AN thoughts and behaviors interfering and disrupting these normal processes. Although weight restoration is a key starting point in FBT, the entire course of treatment takes into consideration the ongoing impact of starvation, cognitions, emotions, and behaviors on adolescent development. These factors associated with maintaining low weight are viewed in FBT as interfering with the adolescent being able to take up the tasks of adolescence and thus must be overcome before fully turning to those broader adolescent tasks. In addition, FBT recognizes that adolescence takes place in the context of family and community and respects the importance of learning in a home environment both for weight gain as well as related developmental tasks to have a lasting effect. Specifically, in this article we describe how the current FBT manualized approach addresses temperament/personality traits, emotional processing, cognitive content and process, social communication and connections, psychiatric comorbidity, and family factors. This report makes no claim to superiority of FBT compared to other therapies in addressing these broader concerns nor does it add interventions to augment the current manual to improve FBT.

Anxiety disorders predict fasting to control weight: A longitudinal large cohort study of adolescents

OBJECTIVE

To determine whether anxiety disorders are prospectively associated with fasting for weight-loss/to avoid weight-gain, a behaviour that precedes and is typical of anorexia nervosa (AN), during adolescence.

METHOD

Participants were 2,406 female adolescents of the Avon Longitudinal Study of Parents and Children. Anxiety disorders were assessed when participants were aged 13-14 and 15-16; fasting was measured approximately 2 years after each anxiety assessment. Generalised estimating equation models examined whether anxiety disorders predicted later fasting, across the two longitudinal waves of data. To probe the moderating effect of time, data were stratified by wave and binary logistic regression analyses completed.

RESULTS

Across longitudinal waves, anxiety disorder presence predicted increased risk of later fasting. Evidence from wave-stratified analyses supported a positive association between anxiety disorder presence at wave 15-16 and fasting at wave 17-18, however did not indicate an association between anxiety disorders at wave 13-14 and fasting at wave 15-16.

DISCUSSION

Anxiety disorder presence in mid-late, but not early, adolescence predicted increased likelihood of later fasting. The differential association could be explained by anxiety being parent-reported at wave 13-14. Findings highlight anxiety disorder pathology as a possible eating disorder prevention target, though the nature of association observed requires clarification.

Altered brain levels of arachidonic acid-derived inflammatory eicosanoids in a rodent model of anorexia nervosa

Increasing evidence underline the role of inflammation in the behavioral, emotional and cognitive dysregulations displayed in anorexia nervosa (AN). Among the inflammatory mediators acting at both peripheral and central levels, growing attention receives a class of lipids derived from arachidonic acid (AA), called eicosanoids (eiCs), which exert a complex, multifaceted role in a wide range of neuroinflammatory processes, peripheral inflammation, and generally in immune system function. To date, little is known about their possible involvement in the neurobiological underpinnings of AN. The present study evaluated whether the activity-based model of AN (ABA) may alter AA-metabolic pathways by changing the levels of AA-derived eiCs in specific brain areas implicated in the development of the typical anorexic-like phenotype, i.e. in prefrontal cortex, cerebral cortex, nucleus accumbens, caudate putamen, amygdala, hippocampus, hypothalamus and cerebellum. Our results point to brain region-specific alterations of the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 epoxygenase (CYP) metabolic pathways rendering altered levels of AA-derived eiCs (i.e. prostaglandins, thromboxanes and hydroxyeicosatetraenoic acids) in response to induction of and recovery from the ABA condition. These changes, supported by altered messenger RNA (mRNA) levels of genes coding for enzymes involved in eiCs-related methabolic pathways (i.e., PLA₂, COX-2, 5-LOX and 15-LOX), underlie a widespread brain dysregulation of pro- and anti-inflammatory eiC-mediated processes in the ABA model of AN. These data suggest the importance of eiCs signaling within corticolimbic areas in regulating key neurobehavioral functions and highlight eiCs as biomarker candidates for monitoring the onset and development of AN, and/or as possible targets for pharmacological management.

A systematic review of studies probing longitudinal associations between anxiety and anorexia nervosa

The current study aimed to establish whether anxiety predicts subsequent anorexia nervosa onset and maintenance. A systematic review of longitudinal studies assessing the association between stable anxiety exposures (e.g. trait anxiety/anxiety disorder pathology) and anorexia nervosa development or maintenance was undertaken. Eight studies met inclusion criteria. Seven probed the association between anxiety and anorexia nervosa onset, and one assessed the association between anxiety and anorexia nervosa maintenance. Individuals with anorexia nervosa were more likely to report childhood anxiety compared to healthy individuals, but whether childhood anxiety explains unique variance in anorexia nervosa development is unclear. Current evidence does not support longitudinal associations between specific anxiety disorders (independently of other anxiety disorders) and subsequent anorexia nervosa onset, however anxiety disorder diagnosis in general may predict increased anorexia nervosa risk. The single study probing the association between anxiety and anorexia nervosa maintenance did not find evidence supporting a relationship. The quality of individual studies was fair to high, however the body of evidence was of low quality. Further research that minimises bias, allowing for strong conclusions concerning longitudinal associations between anxiety and subsequent anorexia nervosa outcomes, is required to inform anorexia nervosa aetiology. This in turn may promote improved prevention and treatment.

Genetic risk factors for eating disorders: an update and insights into pathophysiology

Genome-wide-association studies (GWASs), epigenetic, gene-expression and gene-gene interaction projects, nutritional genomics and investigations of the gut microbiota have increased our knowledge of the pathophysiology of eating disorders (EDs). However, compared with anorexia nervosa, genetic studies in patients with bulimia nervosa and binge-eating disorder are relatively scarce, with the exception of a few formal genetic and small-sized candidate-gene-association studies. In this article, we review important findings derived from formal and molecular genetics in order to outline a genetics-based pathophysiological model of EDs. This model takes into account environmental and nutritional factors, genetic factors related to the microbiome, the metabolic and endocrine system, the immune system, and the brain, in addition to phenotypical traits of EDs. Shortcomings and advantages of genetic research in EDs are discussed against the historical background, but also in light of potential future treatment options for patients with EDs.

The Role of Habits in Anorexia Nervosa: Where We Are and Where to Go From Here?

PURPOSE OF REVIEW

The persistent maladaptive eating behavior characteristic of anorexia nervosa (AN) can be understood as a learned habit. This review describes the cognitive neuroscience background and the existing data from research in AN.

RECENT FINDINGS

Behavior is habitual after it is frequently repeated and becomes nearly automatic, relatively insensitive to outcome, and mediated by dorsal frontostriatal neural systems. There is evidence for such behavior in AN, in which restrictive intake has been related to dorsal frontostriatal systems. Other neural and neurocognitive data provide mixed findings, some of which suggest disturbances in habit systems in AN. There are compelling behavioral and neural data to suggest that habit systems may underlie the persistence of AN. The habit model needs further research, via more direct behavioral hypothesis testing and probes of the development of habitual behavior. Investigation of the habit-centered model of AN may open avenues for the development of novel treatments.

Anxiety and the development and maintenance of anorexia nervosa: protocol for a systematic review

BACKGROUND

Several aetiological models of anorexia nervosa (AN) hold non-eating/weight-gain-related anxiety as a factor relevant to the onset and maintenance of the disorder. Longitudinal studies that allow assessment of this hypothesis have been conducted; however, the evidence has not yet been aggregated in a systematic manner. The proposed study will systematically review articles describing prospective investigations of the relationship between anxiety and AN development or maintenance, with the aim of providing a balanced summary of current understanding and identifying areas for further research.

METHODS/DESIGN

Electronic databases will be searched for articles investigating the longitudinal influence of non-eating/weight-gain-related anxiety (anxiety disorders and trait anxiety) on the development/maintenance of AN. References of eligible articles will be searched to ensure the identification of all relevant studies. Two independent reviewers will complete the title and abstract, and full-text, screening, with a third independent reviewer resolving any conflicts at each stage. A systematic review will be completed, and the quality of the included studies, as well as the strength of the body of evidence generated, will be assessed and reported.

DISCUSSION

Although there are limitations to the present review, understanding the current evidence for the role of non-eating/weight-gain-related anxiety in AN can direct future research that may ensure accurate aetiological models of AN and effective treatments.

SYSTEMATIC REVIEW REGISTRATION

The study is registered on PROSPERO under the reference number CRD42017069644.