The enigmatic persistence of anorexia nervosa

Perspectives and preliminary experiences of psychedelics for the treatment of eating disorders: A systematic scoping review

OBJECTIVE

Research regarding the therapeutic application of psychedelics and psychedelic-assisted psychotherapy in the treatment of eating disorders (EDs) has begun to emerge. This systematic scoping review aimed to map and synthesise the existing evidence regarding the participant reported efficacy and perspectives concerning psychedelics in the treatment of EDs, and to identify significant research gaps.

METHOD

A systematic search was undertaken across several databases in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines.

RESULTS

1290 publications were identified, 1135 after duplicates removed, with 17 meeting full-eligibility criteria. Overall, findings suggested that most participants reported experiencing a meaningful reduction in their ED symptoms and having positive experiences or an openness to explore psychedelics as a treatment for ED symptoms, although some noted concerns of adverse effects and the importance of having psychological support to increase safety and efficacy.

CONCLUSIONS

While preliminary research suggests psychedelics and psychedelic-assisted psychotherapy may be a viable treatment option for ED symptoms, further research with more robust research designs is required to increase confidence in its efficacy, generalisability, and safety as a therapeutic medium.

Habitual behavioural control moderates the relation between daily perceived stress and purging

OBJECTIVE

Evidence suggests that interpersonal stress plays a role in maintaining binge eating and purging (e.g., self-induced vomiting, misuse of laxatives). Stress is especially likely to promote engagement in maladaptive behaviour if the behaviour is habitual; therefore, individuals whose binge eating and/or purging are habitual may be particularly likely to engage in these behaviours in the context of interpersonal stress. We aimed to investigate this hypothesis in a sample of women with binge eating and/or purging using ecological momentary assessment (EMA).

METHOD

Women (N = 81) with binge-eating and/or purging symptoms completed a self-report measure assessing habit strength of binge eating and purging followed by a 14-day EMA protocol assessing daily perceived interpersonal stress and binge-eating and purging episodes.

RESULTS

Habit strength of purging moderated the within-person effect of interpersonal stress on purging frequency, such that higher daily stress was associated with greater same-day purging frequency when purging was more habitual. Contrary to expectations, the interactive effect of habit strength of binge eating and daily interpersonal stress on same-day binge-eating frequency was non-significant.

CONCLUSIONS

Findings suggest that individuals with habitual purging may be vulnerable to engaging in purging when they are experiencing high levels of interpersonal stress.

Trajectories and predictive factors of weight recovery in patients with anorexia nervosa completing treatment. A latent class mixed model approach

BACKGROUND

Treatment of anorexia nervosa (AN) sometimes requires hospitalisation, which is often lengthy, with little ability to predict individual trajectory. Depicting specific profiles of treatment response and their clinical predictors could be beneficial to tailor inpatient management. The aim of this research was to identify clusters of weight recovery during inpatient treatment, and their clinical predictors.

METHODS

A sample of 181 inpatients who completed a treatment programme for AN was included in a retrospective study. A latent class mixed model approach was used to identify distinct weight-gain trajectories. Clinical variables were introduced in a multinomial logistic regression model as predictors of the different classes.

RESULTS

A four-class quadratic model was retained, able to correctly classify 63.7% of the cohort. It encompassed a late-rising, flattening, moderate trajectory of body mass index (BMI) increase (class 1), a late-rising, steady, high trajectory (class 2), an early-rising, flattening, high trajectory (class 3) and an early-rising, steady, high trajectory (class 4). Significant predictors of belonging to a class were baseline BMI (all classes), illness duration (class 2), and benzodiazepine prescription (class 3).

CONCLUSION

Predicting different kinetics of weight recovery based on routinely collected clinical indicators could improve clinician awareness and patient engagement by enabling shared expectations of treatment response.

A transdiagnostic and translational framework for delineating the neuronal mechanisms of compulsive exercise in anorexia nervosa

OBJECTIVE

The development of novel treatments for anorexia nervosa (AN) requires a detailed understanding of the biological underpinnings of specific, commonly occurring symptoms, including compulsive exercise. There is considerable bio-behavioral overlap between AN and obsessive-compulsive disorder (OCD), therefore it is plausible that similar mechanisms underlie compulsive behavior in both populations. While the association between these conditions is widely acknowledged, defining the shared mechanisms for compulsive behavior in AN and OCD requires a novel approach.

METHODS

We present an argument that a better understanding of the neurobiological mechanisms that underpin compulsive exercise in AN can be achieved in two critical ways. First, by applying a framework of the neuronal control of OCD to exercise behavior in AN, and second, by taking better advantage of the activity-based anorexia (ABA) rodent model to directly test this framework in the context of feeding pathology.

RESULTS

A cross-disciplinary approach that spans preclinical, neuroimaging, and clinical research as well as compulsive neurocircuitry and behavior can advance our understanding of when, why, and how compulsive exercise develops in the context of AN and provide targets for novel treatment strategies.

DISCUSSION

In this article, we (i) link the expression of compulsive behavior in AN and OCD via a transition between goal-directed and habitual behavior, (ii) present disrupted cortico-striatal circuitry as a key substrate for the development of compulsive behavior in both conditions, and (iii) highlight the utility of the ABA rodent model to better understand the mechanisms of compulsive behavior relevant to AN.

PUBLIC SIGNIFICANCE

Individuals with AN who exercise compulsively are at risk of worse health outcomes and have poorer responses to standard treatments. However, when, why, and how compulsive exercise develops in AN remains inadequately understood. Identifying whether the neural circuitry underlying compulsive behavior in OCD also controls hyperactivity in the activity-based anorexia model will aid in the development of novel eating disorder treatment strategies for this high-risk population.

Three daily intraperitoneal injections of sub-anesthetic ketamine ameliorate activity-based anorexia vulnerability of adult female mice

OBJECTIVE

To identify ketamine's dosing schedule that ameliorates voluntary food restriction, hyperactivity and body weight loss of adult mice undergoing activity-based anorexia (ABA), an animal model of anorexia nervosa.

METHOD

Female and male C57BL6 mice underwent three cycles of ABA, starting from mid-adolescence. ABA vulnerability was compared within and across two groups of animals: those injected intraperitoneally with 30 mg/kg ketamine for three consecutive days (30mgKetx3) during the second ABA in late adolescence (ABA2) or with vehicle only (Vx3).

RESULTS

Vx3 females and males exhibited individual differences in wheel running and weight retention during first ABA in mid-adolescence (ABA1), ABA2, and third ABA in adulthood (ABA3). Their wheel running correlated with anxiety-like behavior. During ABA1 and ABA3, weight gain of Vx3 females (but not males) after food consumption correlated negatively with food-anticipatory activity (FAA) preceding the feeding hours, indicating that females with higher levels of running restrict feeding more and persistently. This paradoxical relationship confirms earlier findings of ABA females without ketamine treatment, capturing the maladaptive behaviors exhibited by individuals diagnosed with anorexia nervosa. By contrast, 30mgKetx3 had an effect on both sexes of reducing hyperactivity during the feeding hours acutely and reducing anxiety-like behavior's contribution to running. For females, only, 30mgKetx3 acutely improved the extent of compensatory food consumption relative to FAA and improved weight retention during ABA3, 12 days post ketamine in adulthood.

DISCUSSION

Sub-anesthetic ketamine evokes behavior-specific ameliorative effects for adult mice re-experiencing ABA, supporting the notion that multiple doses of ketamine may be helpful in reducing relapse among adults with anorexia nervosa.

PUBLIC SIGNIFICANCE STATEMENT

This study examined whether ketamine reduces anorexia-like behaviors in adult mice. Three daily sub-anesthetic ketamine injections suppress wheel running during and leading up to the hours of food availability and enable animals to compensate better for weight loss associated with excessive exercise by eating more. These findings suggest that ketamine may help adult females diagnosed with anorexia nervosa but also point to sex- and age-related differences in the action of ketamine.

Fatty Acids and Their Lipogenic Enzymes in Anorexia Nervosa Clinical Subtypes

Disordered eating behavior differs between the restricting subtype (AN-R) and the binging and purging subtype (AN-BP) of anorexia nervosa (AN). Yet, little is known about how these differences impact fatty acid (FA) dysregulation in AN. To address this question, we analyzed 26 FAs and 7 FA lipogenic enzymes (4 desaturases and 3 elongases) in 96 women: 25 AN-R, 25 AN-BP, and 46 healthy control women. Our goal was to assess subtype-specific patterns. Lauric acid was significantly higher in AN-BP than in AN-R at the fasting timepoint (p = 0.038) and displayed significantly different postprandial changes 2 h after eating. AN-R displayed significantly higher levels of n-3 alpha-linolenic acid, stearidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid, and n-6 linoleic acid and gamma-linolenic acid compared to controls. AN-BP showed elevated EPA and saturated lauric acid compared to controls. Higher EPA was associated with elevated anxiety in AN-R (p = 0.035) but was linked to lower anxiety in AN-BP (p = 0.043). These findings suggest distinct disordered eating behaviors in AN subtypes contribute to lipid dysregulation and eating disorder comorbidities. A personalized dietary intervention may improve lipid dysregulation and enhance treatment effectiveness for AN.

The explore/exploit trade-off: An ecologically valid and translational framework that can advance mechanistic understanding of eating disorders

The explore/exploit trade-off is a decision-making process that is conserved across species and balances exploring unfamiliar choices of unknown value with choosing familiar options of known value to maximize reward. This framework is rooted in behavioral ecology and has traditionally been used to study maladaptive versus adaptive non-human animal foraging behavior. Researchers have begun to recognize the potential utility of understanding human decision-making and psychopathology through the explore/exploit trade-off. In this article, we propose that explore/exploit trade-off holds promise for advancing our mechanistic understanding of decision-making processes that confer vulnerability for and maintain eating pathology due to its neurodevelopmental bases, conservation across species, and ability to be mathematically modeled. We present a model for how suboptimal explore/exploit decision-making can promote disordered eating and present recommendations for future research applying this framework to eating pathology. Taken together, the explore/exploit trade-off provides a translational framework for expanding etiologic and maintenance models of eating pathology, given developmental changes in explore/exploit decision-making that coincide in time with the emergence of eating pathology and evidence of biased explore/exploit decision-making in psychopathology. Additionally, understanding explore/exploit decision-making in eating disorders may improve knowledge of their underlying pathophysiology, informing targeted clinical interventions such as neuromodulation and pharmacotherapy. PUBLIC SIGNIFICANCE STATEMENT: The explore/exploit trade-off is a cross-species decision-making process whereby organisms choose between a known option with a known reward or sampling unfamiliar options. We hypothesize that imbalanced explore/exploit decision-making can promote disordered eating and present preliminary data. We propose that explore/exploit trade-off has significant potential to advance understanding of the neurocognitive and neurodevelopmental mechanisms of eating pathology, which could ultimately guide revisions of etiologic models and inform novel interventions.

The role of habit in maintaining binge/purge behaviors: An ecological momentary assessment study

OBJECTIVE

Individuals with eating disorders transdiagnostically engage in binge eating (BE) and/or purging, despite life-threatening consequences. Little is known about factors that contribute to the persistence of these behaviors. This study explored whether habitual control over binge/purge (B/P) spectrum behaviors contributes to symptom persistence and whether negative reinforcement via reductions in negative affect is less influential in maintaining B/P behaviors that are under habitual control and are persistent.

METHOD

Women with BE and/or purging (N = 81) completed self-report measures assessing habit strength of BE and purging. Then, they completed a 14-day ecological momentary assessment (EMA) protocol during which they completed measures of negative affect, BE, and purging multiple times per day.

RESULTS

Habitual control over purging was associated with a greater frequency of purging during the EMA period. However, habitual control over BE was not associated with the severity of loss of control eating or the frequency of BE episodes. Habitual control did not moderate temporal relations between negative affect and B/P behaviors during the EMA period. However, exploratory analyses revealed that individuals with a longer duration of BE and greater habitual control over BE showed a less pronounced reduction in negative affect following BE.

DISCUSSION

Overall, these findings suggest that purging may be maintained by habitual stimulus-response learning. In addition, they support the possibility that reduction in negative affect may play a less prominent role in maintaining BE that is habitual and persistent.

PUBLIC SIGNIFICANCE

This study investigated whether habit contributes to the persistence of symptoms in women with binge/purge spectrum behaviors and whether negative reinforcement via reductions in negative affect is less influential in maintaining binge/purge behaviors that are under habitual control. The findings suggest that purging may be maintained through habit. This supports the potential utility of habit reversal interventions to decrease habitual purging.

Affective processes underlying restrictive eating in atypical anorexia nervosa: Comparisons to anorexia nervosa and bulimia nervosa using ecological momentary assessment

OBJECTIVE

Certain symptom and risk/maintenance factor similarities between individuals with atypical anorexia nervosa (AN) and 'typical' AN have been documented, but few studies have investigated how atypical AN compares to bulimia nervosa (BN). Further, the role of affective mechanisms in maintaining restrictive eating in atypical AN has not been examined. The current study investigated whether atypical AN resembles AN and/or BN on affect-related processes using questionnaires and ecological momentary assessment (EMA).

METHOD

Women with atypical AN (n = 24), AN-restrictive subtype, (n = 27), AN-binge eating/purging subtype (n = 34), and BN (n = 58) completed questionnaires measuring depressive symptoms and emotion regulation difficulties. They also completed a 14-day EMA protocol during which they reported negative and positive affect and skipped meals five times/day (signal-contingent surveys) and restrictive eating after meals/snacks (event-contingent surveys).

RESULTS

Diagnostic groups generally did not differ on questionnaire measures nor affective patterns surrounding restrictive eating behaviors. Momentary changes in affect did not predict or follow restriction at meals/snacks, though higher momentary negative affect ratings predicted skipped meals, and higher positive affect was reported after skipped meals. Greater average negative affect and lower average positive affect predicted both restrictive eating behaviors.

DISCUSSION

Across diagnoses, reductions in food intake do not appear to be influenced by momentary changes in affect, though skipping meals may serve an emotion regulation function. Atypical AN seems to resemble AN and BN on affective processes underlying restrictive eating, raising further questions regarding the unique diagnosis of atypical AN.

PUBLIC SIGNIFICANCE

Though atypical anorexia appears to strongly resemble anorexia nervosa, it is less clear how this disorder relates to bulimia nervosa. It is further unknown whether affective-related processes underlie restrictive eating in atypical anorexia nervosa, and how these processes compare to those in anorexia nervosa and bulimia nervosa. Results suggest that atypical anorexia does not differ from anorexia nervosa or bulimia nervosa on emotion-related measures, nor in affective patterns surrounding restrictive eating behaviors.

Temperament impact on eating disorder symptoms and habit formation: a novel model to inform treatment

BACKGROUND

Temperament has long been described as the biological dimension of personality. Due to advancing brain-imaging technology, our understanding of temperament has deepened and transformed over the last 25 years. Temperament combines genetic, neurobiological and trait research. Temperament has been included peripherally in some eating disorder (ED) treatment approaches but has been ignored by most. Temperament fills a fundamental treatment gap by clarifying who is more vulnerable to develop ED and why some individuals are susceptible to specific ED symptoms while others are not. In addition, temperament targets possible treatment solutions.

MAIN TEXT

There is a need for a novel model that incorporates and explores the role of temperament in ED treatment intervention. This paper is a metaphoric temperament model to inform treatment intervention. It describes how temperament traits influences new decisions which impact new behavioural responses. In turn, it neurobiologically tracks how and why the brain efficiently transforms new decisions into new habits. This model integrates both temperament and habit research to explore (a) what temperament is; (b) how new decisions develop into habits neurobiologically; (c) that the brain wires destructive symptoms into habits in the same way that it wires healthy/productive behaviours into habits; (d) traits that trigger ED symptoms are the same traits that influence productive behaviours; and in regard to treatment implications (e) when treatment structure and intervention target client temperaments, the potential for new healthy "trait-syntonic" habits could develop.

CONCLUSIONS

This paper introduces a metaphoric model that synthesizes and integrates temperament neurobiological and trait findings with ED symptoms, habits, and client trait-based solutions. The model synthesizes and integrates different research domains to establish a brain-based foundation to inform treatment intervention. The model targets clients' temperament traits as central collections of innate self-expressions that could be utilized as tools to redirect client trait-syntonic ED responses into trait-syntonic productive outcomes. The brain bases of temperament and habit formation serve as a biological foundation for ED treatment intervention.

Persistent avoidance of virtual food in anorexia nervosa-restrictive type: Results from motion tracking in a virtual stopping task

OBJECTIVE

Food avoidance is central to patients with anorexia nervosa-restrictive type (AN-R). Competing accounts in experimental psychopathology research suggest that food avoidance may result from automatic, habitual responses or from elevated inhibitory control abilities. This study investigated behavioral trajectories of food avoidance in a novel virtual reality stopping task.

METHOD

Sixty patients with AN-R and 29 healthy controls with normal weight were investigated using a novel, kinematic task in virtual reality. We recorded spatial displacement in stop- and go-trials to virtual food and control objects. Inhibitory control abilities were operationalized by the VR task in stopping performance (i.e., interrupted movement in stop-trials), whereas we also measured habitual avoidance of virtual food across both go- and stop-trials (i.e., delayed movement relative to nonfood objects).

RESULTS

In patients with AN-R, hand displacements were shorter to food versus nonfood across stop- and go-trials, reflected in a Stimulus × Group interaction. Healthy controls showed no differences. Importantly, the food-specific effect in AN-R was identical across stop- and go-trials, indicating habitual food avoidance. Moreover, stop error rates (i.e., stop-trials with response) were lower in patients with AN-R.

DISCUSSION

The findings suggest food-specific habitual avoidance and heightened generalized inhibitory control in AN-R. The continuously delayed displacements during active hand movements across stop- and go-trials indicated the persistence of patients' avoidance of food.

PUBLIC SIGNIFICANCE

Experimental research investigates the mechanisms underlying mental disorders such as anorexia nervosa. In this study, we measured interrupted hand movements in response to food pictures or neutral pictures (shoes) in patients with anorexia nervosa and healthy controls. A virtual reality scenario was used. Findings indicated that patients were slower at approaching food, interrupted or not. Key mechanisms of food avoidance can be translated into habit-based treatment options in future research.

Ketamine ameliorates activity-based anorexia of adolescent female mice through changes in GluN2B-containing NMDA receptors at postsynaptic cytoplasmic locations of pyramidal neurons and interneurons of medial prefrontal cortex

Anorexia nervosa (AN) is a mental illness with high rates of mortality and relapse, and no approved pharmacotherapy. Using the activity-based anorexia (ABA) model of AN, we previously showed that a single sub-anesthetic intraperitoneal injection of ketamine (30 mg/kg-KET, but not 3 mg/kg-KET), has an immediate and long-lasting effect of reducing anorexia-like behavior among adolescent female mice. We also showed previously that excitatory outflow from medial prefrontal cortex (mPFC) engages hunger-evoked hyperactivity, leading to the ABA condition of severe weight loss. Ketamine is known to target GluN2B-containing NMDARs (NR2B). Might synaptic plasticity involving NR2B in mPFC contribute to ketamine's ameliorative effects? We addressed this question through electron microscopic immunocytochemical quantification of GluN2B at excitatory synapses of pyramidal neurons (PN) and GABAergic interneurons (IN) in mPFC layer 1 of animals that underwent recovery from a second ABA induction (ABA2), 22 days after ketamine injection during the first ABA induction. The 30 mg/kg-KET evoked synaptic plasticity that differed for PN and IN, with changes revolving the cytoplasmic reserve pool of NR2B more than the postsynaptic membrane pool. Those individuals that suppressed hunger-evoked wheel running the most and increased food consumption during recovery from ABA2 the most showed the greatest increase of NR2B at PN and IN excitatory synapses. We hypothesize that 30 mg/kg-KET promotes long-lasting changes in the reserve cytoplasmic pool of NR2B that enables activity-dependent rapid strengthening of mPFC circuits underlying the more adaptive behavior of suppressed running and enhanced food consumption, in turn supporting better weight restoration.

Neural Response to Expecting a Caloric Sweet Taste Stimulus Predicts Body Mass Index Longitudinally Among Young Adult Women With Anorexia Nervosa

BACKGROUND

Anorexia nervosa (AN) is an often-chronic illness, and we lack biomarkers to predict long-term outcome. Recent neuroimaging studies using caloric taste stimuli suggest that paradigms that have tested conditioned neural responses to expectation or salient stimulus receipt may underpin behaviors. However, whether activation of those neural circuits can predict long-term outcome has not been studied.

METHODS

We followed women treated for AN (n = 35, mean age [SD] = 23 [7] years) and tested whether functional imaging brain response during a taste conditioning paradigm could predict posttreatment body mass index (BMI). We anticipated greater neural activity relative to caloric stimulus expectation and that dopamine-related receipt conditions would predict lower posttreatment BMI, indicating fear-associated arousal.

RESULTS

Follow-up occurred at mean (SD) = 1648 (1216) days after imaging. Stimulus expectation in orbitofrontal and striatal regions and BMI and BMI change at follow-up were negatively correlated, and these correlations remained significant for the right superior orbitofrontal cortex and BMI change after multiple comparison correction (r = -0.484, p = .003). This relationship remained significant after including time between brain scanning and follow-up in the model. Reward prediction error response did not predict long-term BMI.

CONCLUSIONS

The orbitofrontal cortex is involved in learning and conditioning, and these data implicate this region in learned caloric stimulus expectation and long-term prediction of weight outcomes in AN. Thus, conditioned elevated brain response to the anticipation of receiving a caloric stimulus may drive food avoidance, suggesting that breaking such associations is central for long-term recovery from AN.

Greater reliance on model-free learning in adolescent anorexia nervosa: An examination of dual-system reinforcement learning

Alterations in learning and decision-making systems are thought to contribute to core features of anorexia nervosa (AN), a psychiatric disorder characterized by persistent dietary restriction and weight loss. Instrumental learning theory identifies a dual-system of habit and goal-directed decision-making, linked to model-free and model-based reinforcement learning algorithms. Difficulty arbitrating between these systems, resulting in an over-reliance on one strategy over the other, has been implicated in compulsivity and extreme goal pursuit, both of which are observed in AN. Characterizing alterations in model-free and model-based systems, and their neural correlates, in AN may clarify mechanisms contributing to symptom heterogeneity (e.g., binge/purge symptoms). This study tested whether adolescents with restricting AN (AN-R; n = 36) and binge/purge AN (AN-BP; n = 20) differentially utilized model-based and model-free learning systems compared to a healthy control group (HC; n = 28) during a Markov two-step decision-making task under conditions of reward and punishment. Associations between model-free and model-based learning and resting-state functional connectivity between neural regions of interest, including orbitofrontal cortex (OFC), nucleus accumbens (NAcc), putamen, and sensory motor cortex (SMC) were examined. AN-R showed higher utilization of model-free learning compared to HC for reward, but attenuated model-free and model-based learning for punishment. In AN-R only, higher model-based learning was associated with stronger OFC-to-left NAcc functional connectivity, regions linked to goal-directed behavior. Greater utilization of model-free learning for reward in AN-R may differentiate this group, particularly during adolescence, and facilitate dietary restriction by prioritizing habitual control in rewarding contexts.

Impaired implicit learning in adults with anorexia nervosa

OBJECTIVE

Cognitive alterations play an important role in the pathophysiology and treatment of anorexia nervosa (AN). Previous studies suggest that some implicit learning processes may be inhibited in AN. However, this has not yet been fully explored. The purpose of this study is to analyze implicit learning in patients with AN in comparison to healthy controls.

METHODS

In this pilot-study, a total of 21 patients diagnosed with AN and 21 matched controls were administered the weather prediction task (WPT), a probabilistic implicit category learning task that consists of two sub-variants. During the feedback (FB) version of the task, participants learn associations between tarot cards and weather outcomes via an operant learning model through which they receive immediate FB on their answers, whereas during the paired associate (PA) variant, participants are directly asked to memorize given associations.

RESULTS

AN patients showed selective impairment on the FB task where they scored significantly lower both in comparison to controls (p = .001) who completed the same task and when compared to their own performance on the PA variant (p = .006). Clinical measures showed no significant correlations with test scores.

DISCUSSION

Our results demonstrate implicit FB learning deficiencies in adult patients with AN. These impairments may have an impact on the effect of psychotherapeutic interventions and could partially explain the lack of treatment response in AN. Further studies are necessary to derive when and through which mechanisms these alterations originate, and to what extent they should be considered during treatment of the disorder.

PUBLIC SIGNIFICANCE

Cognitive impairments pose a challenge in the management of anorexia nervosa. Improved comprehension of cognitive alterations could lead to a greater understanding of the disease and adaptation of psychotherapeutic treatments. In this study, we found that implicit feedback learning in anorexia nervosa is impaired compared to healthy controls. This could indicate the necessity of treatment adaptations in the form of therapy tools without feedback and a larger focus on psychoeducation.

Back to the future: Progressing memory research in eating disorders

OBJECTIVE

Human behaviors, thoughts, and emotions are guided by memories of the past. Thus, there can be little doubt that memory plays a fundamental role in the behaviors (e.g., binging), thoughts (e.g., body-image concerns), and emotions (e.g., guilt) that characterize eating disorders (EDs). Although a growing body of research has begun to investigate the role of memory in EDs, this literature is limited in numerous ways and has yet to be integrated into an overarching framework.

METHODS

In the present article, we provide an operational framework for characterizing different domains of memory, briefly review existing ED memory research within this framework, and highlight crucial gaps in the literature.

RESULTS

We distinguish between three domains of memory-episodic, procedural, and working-which differ based on functional attributes and underlying neural systems. Most recent ED memory research has focused on procedural memory broadly defined (e.g., reinforcement learning), and findings within all three memory domains are highly mixed. Further, few studies have attempted to assess these different domains simultaneously, though most behavior is achieved through coordination and competition between memory systems. We, therefore, offer recommendations for how to move ED research forward within each domain of memory and how to study the interactions between memory systems, using illustrative examples from other areas of basic and clinical research.

DISCUSSION

A stronger and more integrated understanding of the mechanisms that connect memory of past experiences to present ED behavior may yield more comprehensive theoretical models of EDs that guide novel treatment approaches.

PUBLIC SIGNIFICANCE

Memories of previous eating-related experiences may contribute to the onset and maintenance of eating disorders (EDs). However, research on the role of memory in EDs is limited, and distinct domains of ED memory research are rarely connected. We, therefore, offer a framework for organizing, progressing, and integrating ED memory research, to provide a better foundation for improving ED treatment and intervention going forward.

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.

Parental self-efficacy: Longitudinal impact on clinical outcomes across levels of care in adolescent anorexia nervosa

OBJECTIVE

Parental self-efficacy in the domain of weight restoration for adolescents with restrictive eating disorders is central to success in family-based interventions. We sought to characterize this parental self-efficacy during a brief hospitalization for medical stabilization and follow-up among patients with anorexia nervosa (AN) or atypical AN (AAN) enrolled in the StRONG clinical trial to understand the potential impact of inpatient treatment on caregiver empowerment.

METHODS

Patients were enrolled upon hospital admission and refed per protocol. We examined correlates of the Parents Versus Anorexia (PVA) scale, a measure of parental self-efficacy in the domain of weight restoration, at admission, discharge, 10-days, 1-month, and 3-months post-discharge. Multi-level models evaluated associations among PVA scores and change in %median BMI and Eating Disorder Examination-Questionnaire (EDE-Q) global scores over 3-months post-discharge.

RESULTS

Parents of N = 67 adolescents and young adults M(SD) age 15.79 (2.20) years and 85.00 (11.86) %median BMI participated. PVA scores did not change significantly during hospitalization (p = .053), which lasted on average 10.7 ± 4.5 days. PVA scores increased post-discharge (p = .009), with significant increase between discharge and 1-month post-discharge (p = .045). PVA scores were not associated with subsequent clinical outcomes. Rather, a main effect of time significantly predicted higher %median BMI and improved EDE-Q scores (p < .001).

DISCUSSION

The finding that parental self-efficacy did not deteriorate during the inpatient stay is promising given the medical necessity of hospitalization to ensure short-term safety in some cases and the importance of parental self-efficacy to support long-term recovery.

PUBLIC SIGNIFICANCE

Family-based treatment is the recommended treatment for young people with AN and AAN, serious psychiatric illnesses that may require inpatient medical stabilization. Prior evidence suggests that parental self-efficacy in the outpatient setting is a key component of treatment success. The current study suggests that parental self-efficacy and longer-term treatment outcomes are not undermined by a brief inpatient hospitalization.

Functions of disordered eating behaviors: a qualitative analysis of the lived experience and clinician perspectives

BACKGROUND

One method to improve treatment outcomes for individuals with eating disorders (EDs) may be understanding and targeting individuals' motives for engaging in DE behaviors-or the functions of DE behaviors. The goal of this study was to investigate and categorize the various functions of DE behaviors from the perspectives of adults who engage in DE behaviors and clinicians who treat EDs.

METHODS

Individuals who engage in DE behaviors (n = 16) and clinicians who treat EDs (n = 14) were interviewed, and a thematic analysis was conducted to determine key functions of DE behaviors.

RESULTS

Four main functions of DE behaviors were identified by the authors: (1) alleviating shape, weight, and eating concerns; (2) regulating emotions; (3) regulating one's self-concept; and (4) regulating interpersonal relationships/communicating with others.

CONCLUSIONS

Differences in participant responses, particularly regarding the relevance of alleviating shape and weight concerns as an DE behavior function, highlight the importance of individualized conceptualizations of DE behavior functions for any given client.

Integrating aspects of affect, reward, and cognition to develop more comprehensive models of binge-eating pathology

Reward-related processes are an increasing focus of eating disorders research. Although evidence suggests that numerous distinct reward processes may contribute to eating pathology (e.g., reward learning and delay discounting), existing etiological models of reward dysfunction tend to focus on only a limited number of reward processes, and frequently lack specificity when identifying the individual reward processes hypothesized to contribute to dysregulated eating behavior. Moreover, existing theories have been limited in their integration of reward-related processes with other demonstrated risk and maintenance factors for eating disorders (e.g., affect and cognition), potentially contributing to underdeveloped models of eating pathology. In this article, we highlight five distinct reward processes with theorized or demonstrated relevance to eating disorders involving binge-eating, followed by a review of two well-established risk/maintenance factors for binge-eating pathology. We then introduce two novel models of binge eating onset and maintenance that integrate these factors (i.e., the Affect, Reward, Cognition models), and discuss methods for testing each of the models in future research. Ultimately, we hope that the proposed models provide a springboard for the continued evolution of more precise and comprehensive theories of reward dysfunction in the eating disorders, as well as the development of novel intervention approaches. PUBLIC SIGNIFICANCE STATEMENT: Eating disorders are associated with abnormalities in multiple domains of reward functioning. However, models of reward dysfunction within the eating disorders have not been well-integrated with prominent models of affect and cognition. This article presents two novel models of onset and maintenance for binge-eating pathology, which attempt to integrate observed reward abnormalities with other affective and cognitive processes implicated in binge-type eating disorders.

Large-Scale Exploration of Whole-Brain Structural Connectivity in Anorexia Nervosa: Alterations in the Connectivity of Frontal and Subcortical Networks

BACKGROUND

Anorexia nervosa (AN) is characterized by disturbances in cognition and behavior surrounding eating and weight. The severity of AN combined with the absence of localized brain abnormalities suggests distributed, systemic underpinnings that may be identified using diffusion-weighted magnetic resonance imaging and tractography to reconstruct white matter pathways.

METHODS

Diffusion-weighted magnetic resonance imaging data acquired from female patients with AN (n= 147) and female healthy control (HC) participants (n = 119), ages 12 to 40 years, were combined across 5 studies. Probabilistic tractography was completed, and full-cortex connectomes describing streamline counts between 84 brain regions were generated and harmonized. Graph theory methods were used to describe alterations in network organization in AN. The network-based statistic tested between-group differences in brain subnetwork connectivity. The metrics strength and efficiency indexed the connectivity of brain regions (network nodes) and were compared between groups using multiple linear regression.

RESULTS

Individuals with AN, relative to HC peers, had reduced connectivity in a network comprising subcortical regions and greater connectivity between frontal cortical regions (p < .05, familywise error corrected). Node-based analyses indicated reduced connectivity of the left hippocampus in patients relative to HC peers (p < .05, permutation corrected). Severity of illness, assessed by body mass index, was associated with subcortical connectivity (p < .05, uncorrected).

CONCLUSIONS

Analyses identified reduced structural connectivity of subcortical networks and regions, and stronger cortical network connectivity, among individuals with AN relative to HC peers. These findings are consistent with alterations in feeding, emotion, and executive control circuits in AN, and may direct hypothesis-driven research into mechanisms of persistent restrictive eating behavior.

Can you learn to starve yourself? Inducing food avoidance in the laboratory

The restriction of energy intake is a central and persistent symptom of anorexia nervosa. Recent models of the disorder suggest that food restrictions are learned avoidance behaviours, which are acquired and maintained by classical and operant conditioning. The present study aims to test this learning model of food restriction. It investigates whether introducing negative consequences for the intake of tasty high-calorie food and introducing positive consequences for its avoidance can create food avoidance, increase fear of food, and decrease eating desires in healthy individuals. 104 women were randomly assigned to an experimental or control condition and completed an appetitive conditioning and avoidance learning task. While the experimental condition received money after avoiding the tasty high-calorie food item and heard an aversive sound after not avoiding food intake, the control condition never received these consequences. In the extinction phase, reward and punishment discontinued for both conditions. We measured avoidance frequency, mouse movements, fear, eating desires and stimulus liking. Participants in the experimental condition avoided the food more often than controls and showed increased fear, reduced eating desires and less liking for cues associated with food intake. These results support the notion that food avoidance behaviours, reduced eating desires and fear of food can be learned via classical and operant conditioning. Conditioning paradigms might be a useful tool to study the development and maintenance of food restriction in anorexia nervosa.

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.

Emerging therapeutic targets for anorexia nervosa

INTRODUCTION

Anorexia nervosa is a frequent eating disorder that affects predominantly young women and may take a severe and chronically worsening course of disease contributing to its high mortality rate. Although a multitude of treatment options exist, this disease still bears a high relapse rate. In light of these facts, an improvement of existing and development of new treatment targets and options is warranted.

AREAS COVERED

The present review article covers recent developments in psychotherapy associated with the respective neuropsychological and brain alterations as well as highlights current and future pharmacotherapeutic options.

EXPERT OPINION

Several encouraging developments in the field of psychotherapy such as interventions targeting neurocognitive profiles or addressing reward processing, brain stimulation as well as pharmacological modulation of hormones, namely leptin, oxytocin, ghrelin and nesfatin-1 signaling might be - most likely as part of a multimodal treatment approach - efficacious in order to improve treatment of patients with anorexia nervosa, especially those with a severe course of disease as well as comorbidities. As anorexia nervosa represents a complex and severe mental disorder, it seems most likely that a combination and integration of different evidence-based treatment approaches and settings will contribute to an improved prognosis of this eating disorder. This should be further explored in future studies.

Human habit neural circuitry may be perturbed in eating disorders

Circuit-based mechanisms mediating the development and execution of habitual behaviors involve complex cortical-striatal interactions that have been investigated in animal models and more recently in humans. However, how human brain circuits implicated in habit formation may be perturbed in psychiatric disorders remains unclear. First, we identified the locations of the sensorimotor putamen and associative caudate in the human brain using probabilistic tractography from Human Connectome Project data. We found that multivariate connectivity of the sensorimotor putamen was altered in humans with binge eating disorder and bulimia nervosa and that the degree of alteration correlated with severity of disordered eating behavior. Furthermore, the extent of this circuit aberration correlated with mean diffusivity in the sensorimotor putamen and decreased basal dopamine D2/3 receptor binding potential in the striatum, consistent with previously reported microstructural changes and dopamine signaling mediating habit learning in animal models. Our findings suggest a neural circuit that links habit learning and binge eating behavior in humans, which could, in part, explain the treatment-resistant behavior common to eating disorders and other psychiatric conditions.

Longitudinal study in adolescent anorexia nervosa: evaluation of cortico-striatal and default mode network resting-state brain circuits

Anorexia nervosa (AN) typically emerges in adolescence. The cortico-striatal system (CSTS) and the default mode network (DMN) are brain circuits with a crucial development during this period. These circuits underlie cognitive functions that are impaired in AN, such as cognitive flexibility and inhibition, among others. Little is known about their involvement in adolescent AN and how weight and symptom improvement might modulate potential alterations in these circuits. Forty-seven adolescent females (30 AN, 17 healthy control) were clinically/neuropsychologically evaluated and scanned during a 3T-MRI resting-state session on two occasions, before and after a 6-month multidisciplinary treatment of the AN patients. Baseline and baseline-to-follow-up between-group differences in CSTS and DMN resting-state connectivity were evaluated, as well as their association with clinical/neuropsychological variables. Increased connectivity between the left dorsal putamen and the left precuneus was found in AN at baseline. At follow-up, body mass index and clinical symptoms had improved in the AN group. An interaction effect was found in the connectivity between the right dorsal caudate to right mid-anterior insular cortex, with lower baseline AN connectivity that improved at follow-up; this improvement was weakly associated with changes in neuropsychological (Stroop test) performance. These results support the presence of CSTS connectivity alterations in adolescents with AN, which improve with weight and symptom improvement. In addition, at the level of caudate-insula connectivity, they might be associated with inhibitory processing performance. Alterations in CSTS pathways might be involved in AN from the early stages of the disorder.

Hooked on weight control: An economic theory of anorexia nervosa and its impact on health and longevity

In this paper, I integrate a theory of body image, weight control, and addiction in a life cycle model with health deficit accumulation in order to explain the phenomenon of anorexia nervosa and its impact on health and longevity. Individuals consume normal goods and foods and can work off excess calories with physical exercise. There exists a healthy body mass index and deviations from it increasingly cause health deficits due to obesity or underweight. There exists also a subjective target weight and being heavier than target weight causes a loss of utility from body image. Anorexia is initiated in individuals who are particularly successful in weight control and prone to addiction. Addiction to weight control motivates anorexic individuals to perpetually adjust their target weight downwards and to eat less and exercise more. With declining weight, health deficits accumulate faster and mortality risk rises. I calibrate the model to an average American woman with bmi 28. Due to weight loss addiction, the bmi declines to a level of 15 and causes an expected loss of 15 years of life. I also discuss potential therapies and recovery from the disease.

Clinical and Peripheral Biomarkers in Female Patients Affected by Anorexia: Does the Neutrophil/Lymphocyte Ratio (NLR) Affect Severity?

Anorexia Nervosa (AN) is a disabling disorder characterized by extreme weight loss and frequent chronicization, especially in its most severe forms. This condition is associated with a pro-inflammatory state; however, the role of immunity in symptom severity remains unclear. Total cholesterol, white blood cells, neutrophils, lymphocytes, platelets, iron, folate, vitamin D and B12 were dosed in 84 female AN outpatients. Mildly severe (Body Mass Index-BMI ≥ 17) versus severe (BMI < 17) patients were compared using one-way ANOVAs or χ² tests. A binary logistic regression model was run to investigate the potential association between demographic/clinical variables or biochemical markers and the severity of AN. Patients with severe anorexia (compared to mild forms) were older (F = 5.33; p = 0.02), engaged in more frequent substance misuse (χ² = 3.75; OR = 3.86; p = 0.05) and had a lower NLR (F = 4.12; p = 0.05). Only a lower NLR was predictive of severe manifestations of AN (OR = 0.007; p = 0.031). Overall, our study suggests that immune alterations may be predictive of AN severity. In more severe forms of AN, the response of the adaptive immunity is preserved, while the activation of the innate immunity may be reduced. Further studies with larger samples and a wider panel of biochemical markers are needed to confirm the present results.

New Perspective on Anorexia Nervosa: Tryptophan-Kynurenine Pathway Hypothesis

Anorexia nervosa (AN), affecting up to 4% of all females and 0.3% of all males globally, remains the neuropsychiatric disorder with the highest mortality rate. However, the response to the current therapeutic options is rarely satisfactory. Considering the devastating prognosis of survival among patients with AN, further research aimed at developing novel, more effective therapies for AN is essential. Brain and serum tryptophan is mostly converted along the kynurenine pathway into multiple neuroactive derivatives, whereas only 1-2% is used for the synthesis of serotonin. This narrative review provides an update on the experimental and clinical research data concerning the metabolism of tryptophan along the kynurenine pathway in anorexia nervosa based on the available literature. We propose that in AN, lower levels of L-kynurenine and kynurenic acid result in diminished stimulation of the aryl hydrocarbon receptor, which could contribute to abnormally low body weight. The impact of L-kynurenine supplementation on anorexia in animal models and the effects of changes in tryptophan and downstream kynurenines on the clinical progression of AN require further investigation. Moreover, prospective clinical studies on larger cohorts of restrictive and binge-eating/purging AN patients and assessing the potential benefit of L-kynurenine as an add-on therapeutic agent, should follow.

Learned industriousness as a translational mechanism in anorexia nervosa

It remains unexplained why some behaviours persist despite being non-hedonic and ostensibly aversive. This phenomenon is especially baffling when such behaviours are taken to excess in the form of psychopathology. Anorexia nervosa is one psychiatric disorder in which effortful behaviours that most people find unpleasant (suchas restrictive eating) are persistently performed. We propose thatthe social psychology theory of learned industriousness providesa novel mechanistic account for such phenomena. This theoryposits that high-effort behaviour can be conditioned to acquire secondary reinforcing properties through repeated pairing with reward. Accordingly, effort sensations become less aversive andmore appetitive, increasing willingness to engage in effortful behaviour. In this Perspective, we review pre-clinical behaviouraland biological data that support learned industriousness, contrast learned industriousness with other models of non-hedonic persistence (such as habit learning), highlight evidence that supports learned industriousness in individuals with anorexia nervosa and consider implications of the model, including translation to other psychiatric presentations.

Ketamine ameliorates activity-based anorexia of adolescent female mice through changes in the prevalence of NR2B-containing NMDA receptors at excitatory synapses that are in opposite directions for of pyramidal neurons versus GABA interneurons In medial prefrontal cortex

A previous study showed that a single sub-anesthetic dose of ketamine (30 mg/kg-KET, IP) has an immediate and long-lasting (>20 days) effect of reducing maladaptive behaviors associated with activity-based anorexia (ABA) among adolescent female mice. This study sought to determine whether synaptic plasticity involving NR2B-containing NMDA receptors (NR2B) at excitatory synapses in the prelimbic region of medial prefrontal cortex (mPFC) contributes to this ameliorative effect. To this end, quantitative electron microscopic analyses of NR2B-subunit immunoreactivity at excitatory synapses of pyramidal neurons (PN) and GABAergic interneurons (GABA-IN) were conducted upon layer 1 of mPFC of the above-described mice that received a single efficacious 30 mg/kg-KET (N=8) versus an inefficacious 3 mg/kg-KET (N=8) dose during the food-restricted day of the first ABA induction (ABA1). Brain tissue was collected after these animals underwent recovery from ABA1, then of recovery from a second ABA induction (ABA2), 22 days after the ketamine injection. For all three parameters used to quantify ABA resilience (increased food consumption, reduced wheel running, body weight gain), 30 mg/kg-KET evoked synaptic plasticity in opposite directions for PN and GABA-IN, with changes at excitatory synapses on GABA-IN dominating the adaptive behaviors more than on PN. The synaptic changes were in directions consistent with changes in the excitatory outflow from mPFC that weaken food consumption-suppression, strengthen wheel running suppression and enhance food consumption. We hypothesize that 30 mg/kg-KET promotes these long-lasting changes in the excitatory outflow from mPFC after acutely blocking the hunger and wheel-access activated synaptic circuits underlying maladaptive behaviors during ABA.

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.

A systematic review comparing atypical anorexia nervosa and anorexia nervosa

OBJECTIVE

A description of atypical anorexia nervosa (atypical AN) was provided in DSM-5 in 2013 and a sizable literature has since developed describing the clinical features of individuals with atypical AN and comparing them to those of individuals with anorexia nervosa (AN) and those of healthy individuals. The purpose of this study was to conduct a systematic review of this literature.

METHOD

A systematic review following PRISMA guidelines was conducted of studies published since 2013 that compared the clinical characteristics of individuals with atypical AN to those of individuals with AN and/or healthy controls. Meta-analyses were conducted when similar measures were reported in three or more studies.

RESULTS

Twenty-four publications met criteria for inclusion. Their results indicated that the level of eating disorder-specific psychopathology is significantly higher among individuals with atypical AN than among controls and as high or higher as among individuals with AN while levels of non-eating disorder psychopathology are similar. Individuals with atypical AN experience many of the physiological complications associated with AN, but some complications appear less frequent.

DISCUSSION

The psychological symptoms and physiological complications of individuals with atypical AN are generally similar to those of individuals with AN, although there may be differences in the frequency of some physical complications. Little information is available on the course, outcome, and treatment response of individuals with atypical AN. In addition, full diagnostic criteria for atypical AN have not been developed, and the nosological relationship of atypical AN to established eating disorders such as bulimia nervosa is unclear.

PUBLIC SIGNIFICANCE

Atypical anorexia nervosa as described in the DSM-5 identifies individuals with many of the psychological characteristics of typical anorexia nervosa who, despite significant weight loss, are not underweight. The current systematic review found that the psychological symptoms and physiological characteristics of individuals with atypical AN are generally similar to those of individuals with AN, although there may be differences in the frequency of some physical complications.

Psychedelic-Assisted Therapy for People with Eating Disorders

PURPOSE OF REVIEW

A growing body of research suggests psychedelic-assisted therapy (PAT) may be safe and effective for a variety of mental health conditions. Among these, eating disorders have been a recent target of interest. This review provides an up-to-date summary of the potential mechanisms and use of PAT in people diagnosed with eating disorders, with a focus on anorexia nervosa.

RECENT FINDINGS

Classic psychedelics may have transdiagnostic efficacy through several mechanisms relevant to eating disorder pathology. Interest in, and efforts to increase access to PAT are both high. Early clinical trials are focused on establishing the safety and utility of this treatment in eating disorders, and efficacy remains unclear. High-quality published data to support the use of PAT for people with eating disorders remains lacking. Recent studies however suggest PAT has the potential to augment the efficacy of current interventions for these difficult-to-treat conditions.

Conditional effects of state fear of negative evaluation on restrictive eating behaviors

Fear of being evaluated negatively by others is a risk factor for the development of disordered eating. Specifically, trait level fear of negative evaluation (FNE) predicts disordered eating severity above other social anxiety traits. However, it remains unclear how state levels of this fear may impact eating behavior. The current study aimed to examine this risk factor in the context of state-level eating behavior. We hypothesized that: (a) elevated levels of state FNE would enhance the relationship between restraint and restriction and (b) we sought to explore the predictive nature of high trait FNE on restriction. Study procedures for N = 64 undergraduate students included assessment of dietary restraint, fear of negative evaluation, and hypothetical meal choice in the context of several proposed social and non-social settings. Results indicated that higher state FNE was related to more restrictive food choice across settings, and levels of trait FNE were not related to food choices. State FNE did not enhance the relationship between restraint and restriction. This project sought to examine the degree to which fear of negative evaluation impacts the relationship between dietary restraint and restriction, testing a unique risk factor for the development of eating psychopathology.

Smaller putamen volumes are associated with greater problems in external emotional regulation in depressed adolescents with nonsuicidal self-injury

The functions of nonsuicidal self-injury (NSSI) consist of social and emotional aspects (Social influence, Sensation seeking, Internal and External emotion regulation). Previous studies have indicated that dysfunction in reward-related brain structures especially the striatum might drive this habitual behavior. However, no studies to date have investigated the associations between striatum and different functions for adolescents engaging in NSSI behaviors. Here, we recruited 35 depressed adolescents with recent NSSI behaviors and 36 healthy controls and acquired structural brain images, depressive symptoms, social, academic and family environments assessments, in addition to NSSI functions in patients only. Subcortical volumes and cortical thickness were estimated with FreeSurfer. Mixed linear regressions were performed to examine associations between striatal structures (caudate, putamen, nucleus accumbens, pallidum) and NSSI functions, with age, sex, total intracranial volume, hemisphere and depression severity included as covariates. Effect of environmental factors and potential associations with cortical thickness and other subcortical volumes were also tested. We found that, among the four functions, external emotional regulation represented the main function for NSSI engagement. Increased external emotion regulation was significantly associated with smaller putamen volume. No environmental factors biased the association with putamen. No associations with other cortical or subcortical regions were observed. Our findings suggested that smaller putamen might be a biomarker of NSSI engagement for depressed adolescents when they regulated frustrated or angry emotions. The results have potentially clinical implications in early identification and brain intervention of NSSI in youth.

The Fitter I Am, the Larger I Feel-The Vicious Circle of Physical Exercise in Anorexia Nervosa

Introduction: Body image distortion is a core symptom of anorexia nervosa (AN), embodying dissatisfaction and overvaluation of body appearance and weight. Body image distortion is an important factor in the maintenance of weight loss behaviours such as compulsive physical exercise. Conversely, physical exercise seems to have an aggravating effect on body image in patients with AN, but the evidence is still poor. The aim of this study was to examine the relationship between body image distortion and physical exercise in AN in order to understand whether physical exercise may play a specific role in body image distortion beyond psychopathological severity. Methods: Forty patients with AN and 21 healthy controls were tested for body image distortion and different proxies of physical exercise. Univariate correlations tested the relationship between body image distortion and physical exercise in AN and control groups. Then, to experimentally assess the effect of exercise on body image distortion, participants were invited to rate their body image before and after a standardised effort test. Results: In the AN group, a correlation was found between physical activity and body image distortion (p < 0.01), which was still significant after controlling for psychopathological severity. No correlation was found in healthy controls. After a standardised effort, patients with AN had higher increases in body image distortion than healthy controls (almost 4 kg/m2 vs. 0.8 kg/m2) (p < 0.01). Discussion: Physical exercise may contribute to the distortion of body image in anorexia nervosa and explain the paradoxical augmentation of unhealthy exercise despite ongoing weight loss.

Pathway-specific GABAergic inhibition contributes to the gain of resilience against anorexia-like behavior of adolescent female mice

Anorexia nervosa is one of the most debilitating mental illnesses that emerges during adolescence, especially among females. Anorexia nervosa is characterized by severe voluntary food restriction and compulsive exercising, which combine to cause extreme body weight loss. We use activity-based anorexia (ABA), an animal model, to investigate the neurobiological bases of vulnerability to anorexia nervosa. This is a Mini-Review, focused on new ideas that have emerged based on recent findings from the Aoki Lab. Our findings point to the cellular and molecular underpinnings of three ABA phenomena: (1) age-dependence of ABA vulnerability; (2) individual differences in the persistence of ABA vulnerability during adolescence; (3) GABAergic synaptic plasticity in the hippocampus and the prefrontal cortex that contributes to the suppression of the maladaptive anorexia-like behaviors. We also include new data on the contribution to ABA vulnerability by cell type-specific knockdown of a GABA receptor subunit, α4, in dorsal hippocampus. Although the GABA system recurs as a key player in the gain of ABA resilience, the data predict why targeting the GABA system, singularly, may have only limited efficacy in treating anorexia nervosa. This is because boosting the GABAergic system may suppress the maladaptive behavior of over-exercising but could also suppress food consumption. We hypothesize that a sub-anesthetic dose of ketamine may be the magic bullet, since a single injection of this drug to mid-adolescent female mice undergoing ABA induction enhances food consumption and reduces wheel running, thereby reducing body weight loss through plasticity at excitatory synaptic inputs to both excitatory and inhibitory neurons. The same treatment is not as efficacious during late adolescence but multiple dosing of ketamine can suppress ABA vulnerability partially. This caveat underscores the importance of conducting behavioral, synaptic and molecular analyses across multiple time points spanning the developmental stage of adolescence and into adulthood. Since this is a Mini-Review, we recommend additional literature for readers seeking more comprehensive reviews on these subjects.

Increased Habit Frequency in the Daily Lives of Patients with Acute Anorexia Nervosa

Strict eating routines and frequent rigid behavior patterns are commonly observed in patients with anorexia nervosa (AN). A recent theory proposes that while these behaviors may have been reinforced initially, they later become habitual. To date, however, research has been overly focused on eating-disorder (ED)-related habits. Over the course of seven days, we applied an ecological momentary assessment (EMA) to investigate the habit frequency and strength of ED-specific (food intake) and ED-unspecific (hygiene) habits in the daily lives of a sample of n = 57 AN and n = 57 healthy controls (HC). The results of the hierarchical models revealed that habits were significantly more likely in patients compared with HC for both categories, independently. Furthermore, a lower body mass index (BMI) was associated with increased habit frequency in AN. Our study strengthens the habit theory of AN by showing the relevance of habits beyond ED-specific behavioral domains. This also supports the development of innovative therapeutic interventions targeting habitual behavior in EDs.

Understanding relations between intolerance of uncertainty and body checking and body avoiding in anorexia nervosa

BACKGROUND

A key feature of anorexia nervosa is body image disturbances and is often expressed by dysfunctional body-related behaviours such as body checking and body avoiding. These behaviours are thought to contribute to both the maintenance and relapse of AN, yet empirical evidence is scarce. One variable that may contribute to the need for engaging in these behaviours is intolerance of uncertainty. This study aims to investigate body checking and body avoiding and its relations with intolerance of uncertainty in women with anorexia nervosa (AN-ill; 70), women recovered from AN (AN-rec; 85) and control group (127).

METHODS

Three questionnaires were completed, measuring eating pathology, intolerance of uncertainty and body checking and body avoiding. One-way ANOVAS were used to test group differences. Moderation analyses were used to investigate associations between variables.

RESULTS

Levels of intolerance of uncertainty, body checking and body avoiding were highest in AN-ill followed by AN-rec and, lastly, the control group, confirming group differences. Intolerance of uncertainty was associated with body checking in the AN-rec group and the control group but not in the AN-ill group. The association between intolerance of uncertainty and body avoiding was reported in the AN-rec group and only marginally in the control group.

CONCLUSION

Levels of intolerance of uncertainty, body checking and body avoiding were highest in AN-ill, however still elevated in AN-rec, confirming the presence of body image disturbances, even after recovery. The unique associations between intolerance of uncertainty and body checking and body avoiding within the studied groups may represent different stages of the illness. In the AN-rec group, the relation between intolerance of uncertainty, body checking and body avoiding may be driven by trait anxiety. For AN-ill group, body checking and body avoiding may eventually have grown into habitual patterns, rather than a strategy to ameliorate anxiety and uncertainty. Women with anorexia nervosa often experience disturbances in their body image and are expressed in body-related behaviours such as body checking and body avoiding. These behaviours are thought to contribute to both the maintenance and relapse of anorexia nervosa. Intolerance of uncertainty is defined as the incapacity to tolerate uncertainty and may contribute to the need for engaging in these behaviours. This study aims to investigate body checking and body avoiding and its relations with intolerance of uncertainty in women with anorexia nervosa (AN-ill; 70), women recovered from AN (AN-rec; 85) and control group (127). Three questionnaires were completed, measuring eating pathology, intolerance of uncertainty and body checking and body avoiding. Levels of intolerance of uncertainty, body checking and body avoiding were highest in AN-ill and still elevated in AN-rec, even after recovery. The associations between intolerance of uncertainty and body checking and body avoiding within the studied groups may represent different stages of the illness. In the AN-rec group, the relation between intolerance of uncertainty, body checking and body avoiding may be driven by trait anxiety. For AN-ill group, body checking and body avoiding may have grown into habitual patterns, rather than a strategy to ameliorate anxiety and uncertainty.

A scoping review of non-specific predictors, moderators, and mediators of family-based treatment for adolescent anorexia and bulimia nervosa: a summary of the current research findings

PURPOSE

This scoping review presents an up-to-date synthesis of the current evidence base for non-specific predictors, moderators, and mediators of family-based treatment (FBT) for adolescent anorexia and bulimia nervosa.

METHODS

We identify ways in which end-of-treatment outcomes have been shown to differ based upon baseline clinical features and person-specific factors and explore psychological mechanisms that may explain differences in treatment response. We draw from this evidence base to outline recommendations for clinical practice, as well as directions for future clinical eating disorder research.

RESULTS

Noted findings from review include that early response in weight gain and parental criticism may be particularly influential in treatment for anorexia nervosa. Further, for adolescents with either anorexia or bulimia nervosa, eating-related obsessionality may be a key intervention target to improve outcomes.

CONCLUSION

In addition to highlighting a need for attention to specific patient- and caregiver-level factors that impact treatment response, recommendations for research and clinical practice include testing whether certain targeted treatments (e.g., exposure-based approaches) may be suitable within the context of FBT for eating disorders.

LEVEL OF EVIDENCE

Level I: Evidence obtained from: at least one properly designed randomized controlled trials; experimental studies.

Sense of agency during and following recovery from anorexia nervosa

The need to feel in control is central to anorexia nervosa (AN). The sense of control in AN has only been studied through self-report. This study investigated whether implicit sense of control (sense of agency; SoA) differs across AN patients, recovered AN (RAN) patients and healthy controls (HC). Furthermore, we assessed whether state anxiety is influenced by negative emotional states. SoA was measured with the intentional binding task (IB) and state-anxiety levels through a questionnaire. We did not find any evidence of differences in SoA between groups. Furthermore, state anxiety was not a significant predictor of SoA. Further research into SoA in AN should focus on other features of the SoA that are not targeted by the IB task.

Optimizing relapse prevention and changing habits (REACH+) in anorexia nervosa

INTRODUCTION

Relapse rates in anorexia nervosa (AN) are high, even after full weight restoration. This study aims to develop a relapse prevention treatment that specifically addresses persistent maladaptive behaviors (habits). Relapse Prevention and Changing Habits (REACH+) aims to support patients in developing routines that promote weight maintenance, encourage health, and challenge habits that perpetuate illness. The clinical trial design uses the Multiphase Optimization STrategy (MOST) framework to efficiently identify which components of treatment contribute to positive outcomes.

METHODS

Participants will be 60 adults with AN who have achieved weight restoration in an inpatient setting. Treatment will consist of 6 months of outpatient telehealth sessions. REACH+ consists of behavior, cognitive, and motivation components, as well as food monitoring and a skill consolidation phase. A specialized online platform extends therapy between sessions. Participants will be randomly assigned to different versions of each component in a fractional factorial design. Outcomes will focus on maintenance of remission, measured by rate of weight loss and end-of-trial status. Interventions that contribute to remission will be included in an optimized treatment package, suitable for a large-scale clinical trial of relapse prevention in AN.

Biased and inflexible interpretations of ambiguous social situations: Associations with eating disorder symptoms and socioemotional functioning

BACKGROUND

Research indicates that difficulties across multiple socioemotional functioning domains (e.g., social emotion expression/regulation, response to social elicitors of emotion) and negatively biased interpretations of ambiguous social situations may affect eating disorder symptoms. The impact of inflexible interpretations of social situations on eating disorder symptoms is less clear. The present study therefore examined relations between inflexible and biased social interpretations, socioemotional functioning, and eating disorder symptoms.

METHOD

A total of 310 participants from the general population, recruited from an online crowdsourcing platform, completed measures of socioemotional functioning (e.g., rejection sensitivity, negative social exchange), eating disorder symptoms, and positive and negative interpretation bias and inflexibility on a single measurement occasion.

RESULTS

Socioemotional functioning impairments (Pillai's trace = 0.11, p < .001), but not negative (β = .07, p = .162) or positive (β = -.01, p = .804) interpretation bias or inflexible interpretations (β = .04, p = .446), were associated with eating disorder symptoms in multiple regression models. In network analyses controlling statistically for multiple markers of socioemotional functioning, eating disorder symptoms were directly associated with negative (but not positive) interpretation bias. Inflexible interpretations were indirectly linked to symptoms via co-dampening of positive emotions. Exploratory causal discovery analyses suggested that several socioemotional functioning variables (social anxiety, depression, negative social exchange) may cause eating disorder symptoms.

CONCLUSIONS

Consistent with cognitive-interpersonal models of disordered eating, our results suggest that less accurate (biased, inflexible) interpretations of social information contribute to patterns of cognition (anxious anticipation of rejection) and emotion regulation (down-regulation of positive social emotion) thought to encourage disordered eating.

PUBLIC SIGNIFICANCE

This study suggests that less accurate interpretations of ambiguous social information encourage anxious anticipation of rejection and downregulation of positive social emotions, both of which are thought to promote eating disorder symptoms. Knowledge provided by this study about the likely relations between interpretive processes, social/emotional functioning, and eating disorder symptoms may help inform treatments for eating disorders, particularly those that attempt to modify patterns of interpretation.

Behavioral reinforcement of pathological exercise in anorexia nervosa

Pathological exercise in anorexia nervosa (AN) is a harmful behavior associated with a chronic course and poor prognosis. To date, no comprehensive theoretical model exists to describe pathological exercise in the context of AN, and as such, few treatments are effective at promoting direct and sustained pathological exercise extinction. Using a framework put forth by Wise & Koob (2014), debating the relative importance of positive and negative reinforcement in substance use, we present three hypotheses of behavioral reinforcement of exercise, encompassing biological, psychological, and environmental influences. Specifically, we argue that exercise is positively reinforced through receipt of biological and behavioral rewards, negatively reinforced through avoidance of aversive emotions, and that these two systems work in tandem over time to engrain pathological exercise as a habit. We then present suggestions for testing each of these hypotheses as future directions for the field.

'In an otherwise limitless world, I was sure of my limit.'† Experiencing Anorexia Nervosa: A phenomenological metasynthesis

Anorexia Nervosa (AN) has the highest mortality rate of the mental disorders, with still less than 50% of affected individuals achieving recovery. Recent calls to bring innovative, empirical research strategies to the understanding of illness and its core psychopathological features highlight the need to address significant paucity of efficacious treatment. The current study brings a phenomenological approach to this challenge, synthesizing lived experience phenomena as described by qualitative literature. Fifty-three studies published between the years 1998 and 2021 comprising a total of 1557 participants aged 12-66 suffering from AN or sub-threshold AN are included. Reciprocal and refutational analysis generated six key third-order constructs: "emotion experienced as overwhelming," "identity," "AN as a tool," "internal conflict relating to Anorexia," "interpersonal communication difficulties" and "corporeality." Twenty-six sub-themes were identified, the most common being fear, avoidance, AN as guardian/protector, and AN as intertwined with identity. Some themes associated with current treatment models such as low self-esteem, need for social approval and feelings of fatness were less common. We highlight the significant role of intense and confusing emotion in AN, which is both rooted in and engenders amplified fear and anxiety. Restrictive eating functions to numb these feelings and withdraw an individual from a chaotic and threatening world whilst providing a sense of self around which to build an illness identity. Results have implications for therapeutic practice and overly protective weight and shape focused medical treatment models, which may serve to reinforce the disease.

I change my mind to get better: Process tracing-based microanalysis of food choice processes reveals differences between anorexia nervosa and bulimia nervosa during inpatient treatment

Food choice and its underlying processes is understudied in bulimia nervosa (BN) and anorexia nervosa (AN). Thus, we examined cognitive processes during food choice through mouse tracing in AN (n = 36) and BN (n = 27) undergoing inpatient treatment. Both patient groups and matched healthy controls (HC, n = 59) made 153 binary food choices before rating all foods on their liking and calorie density. Choice outcomes and corresponding mouse movements were modelled as a function of inpatient treatment stage in our analyses. Compared to patients with BN and HC, those with AN showed a clear calorie avoidance on most trials. Yet, mouse paths in AN patients early in treatment, revealed a late direction reversal ('change of mind', CoM) on high-calorie choices. AN patients later in treatment, by contrast, showed fewer CoM alongside more choices for - and liking of - high-calorie foods. Patients with BN showed more CoM trials during low-calorie choices and low-calorie choices were more frequent in patients later in treatment. Thus, relative to patients early in treatment, patients who are later in treatment show less of the overall group pattern of consistently choosing low-calorie food (AN) or high-calorie food (BN). Less cognitive regulation (fewer CoM trials) went along with higher liking for high-calorie foods in AN. These cross-sectional differences between AN early and late in treatment might reflect the formation of healthier habits. In addition, clear patient group differences suggest more specific treatment strategies.

Is decision-making impairment an endophenotype of anorexia nervosa?

Background

Patients with anorexia nervosa (AN) show impaired decision-making ability, but it is still unclear if this is a trait marker (i.e., being associated with AN at any stage of the disease) or a state parameter of the disease (i.e., being present only in acutely ill patients), and if it has endophenotypic characteristics. The aim of this study was to determine the endophenotypic, and state- or trait-associated nature of decision-making impairment in AN.

Methods

Ninety-one patients with acute AN (A-AN), 90 unaffected relatives (UR), 23 patients remitted from AN (R-AN), and 204 healthy controls (HC) carried out the Iowa gambling task (IGT). Prospective valence learning (PVL) model was employed to distinguish the cognitive dimensions underlying the decision-making process, that is, learning, consistency, feedback sensitivity, and loss aversion. IGT performance and decision-making dimensions were compared among groups to assess whether they had endophenotypic (i.e., being present in A-AN, UR, and R-AN, but not in HC) and/or trait-associated features (i.e., present in A-AN and R-AN but not in HC).

Results

Patients with A-AN had lower performance at the IGT (p < 0.01), while UR, R-AN, and HC had comparable results. PVL-feedback sensitivity was lower in patients with R-AN and A-AN than in HC (p < 0.01).

Conclusions

Alteration of decision-making ability did not show endophenotypic features. Impaired decision-making seems a state-associated characteristic of AN, resulting from the interplay between trait-associated low feedback sensitivity and state-associated features of the disease.