Disordered eating behaviors and reward sensitivity

Neural correlates associated with processing food stimuli in anorexia nervosa and bulimia nervosa: an activation likelihood estimation meta-analysis of fMRI studies

PURPOSE

Various neurobiological models have utilised symptom categories to explore the underlying neural correlates in both anorexia nervosa (AN) and bulimia nervosa (BN). The aim of this research was to investigate the brain activity patterns associated with viewing food stimuli in anorexia nervosa and bulimia nervosa.

METHODS

Electronic databases including PsycInfo and PubMed were systematically searched from data base inception until 1st of December 2020, identifying 14 suitable functional magnetic resonance imaging studies (fMRI), involving 470 participants. ALE meta-analysis was used to statistically analyse the overlap of activation foci from different fMRI studies in response to visual food stimuli.

RESULTS

Comparing patients with AN with healthy control (HC), we detected hypoactivation in brain areas related to reward processing (i.e., amygdala and lentiform nucleus), and interoceptive processing (i.e., insula). In addition, patients with AN showed hyperactivations in cognitive control areas (i.e., prefrontal and anterior cingulate cortex). In contrast, patients with BN exhibited hyperactivations in brain areas related to reward processing (i.e., lentiform nucleus), and interoceptive processing (i.e., insula). Furthermore, patients with BN showed hypoactivations in brain regions associated with cognitive control (i.e., prefrontal and anterior cingulate cortex).

CONCLUSIONS

Our study shows differing neural endotypes of the two types of eating disorders, that underpin their behavioural phenotypes. While exploratory in nature, these findings might be relevant for guiding new emerging therapies, including invasive and non-invasive neuromodulation techniques in treatment of eating disorders.

LEVEL OF EVIDENCE

Level I, meta-analysis.

Social reward and social punishment sensitivity in relation to dietary restraint and binge/purge symptoms

Disordered eating symptoms are associated with disrupted sensitivity to reward and punishment, broadly assessed. However, it is unknown how eating pathology is related to sensitivity to social reward and social punishment specifically. Drawing on Reinforcement Sensitivity Theory, the current study utilized a multi-method design to test whether disordered eating symptoms, specifically dietary restraint (DR) and binge/purge (BP), were similarly or uniquely related to sensitivity to social punishment and social reward. Female university students (N = 110, M = 18.66, SD = 0.89) completed self-report measures and a novel behavioral task measuring willingness to work for or to avoid social feedback. DR and BP symptoms were related to increased self-reported and behavioral sensitivity to social punishment, yet only when symptoms were tested in isolation. DR was associated with increased sensitivity to social reward across self-report and behavioral paradigms. BP symptoms were uniquely and positively related to self-reported sensitivity to social reward, but decreased behavioral sensitivity to social reward. Findings suggest that sensitivity to punishment may be a common factor related to DR and BP, whereas sensitivity to social reward may be a key factor differentiating disordered eating symptoms.

Exploring the Relationship between Reward and Punishment Sensitivity and Gambling Disorder in a Clinical Sample: A Path Modeling Analysis

Most individuals will gamble during their lifetime, yet only a select few will develop gambling disorder. Gray's Reinforcement Sensitivity Theory holds promise for providing insight into gambling disorder etiology and symptomatology as it ascertains that neurobiological differences in reward and punishment sensitivity play a crucial role in determining an individual's affect and motives. The aim of the study was to assess a mediational pathway, which included patients' sex, personality traits, reward and punishment sensitivity, and gambling-severity variables. The Sensitivity to Punishment and Sensitivity to Reward Questionnaire, the South Oaks Gambling Screen, the Symptom Checklist-Revised, and the Temperament and Character Inventory-Revised were administered to a sample of gambling disorder outpatients (N = 831), diagnosed according to DSM-5 criteria, attending a specialized outpatient unit. Sociodemographic variables were also recorded. A structural equation model found that both reward and punishment sensitivity were positively and directly associated with increased gambling severity, sociodemographic variables, and certain personality traits while also revealing a complex mediational role for these dimensions. To this end, our findings suggest that the Sensitivity to Punishment and Sensitivity to Reward Questionnaire could be a useful tool for gaining a better understanding of different gambling disorder phenotypes and developing tailored interventions.

Eating disorders: Insights from imaging and behavioral approaches to treatment

Understanding factors that contribute to eating disorders, which affect 13% of females, is critical to developing effective prevention and treatment programs. In this paper, we summarize results from prospective studies that identified factors predicting onset and persistence of eating disorders and core symptom dimensions. Next, implications for intervention targets for prevention, and treatment interventions from the risk- and maintenance-factor findings are discussed. Third, given that evidence suggests eating disorders are highly heritable, implying biological risk and maintenance factors for eating disorders, we offer working hypotheses about biological factors that might contribute to eating disorders, based on extant risk factor findings, theory, and cross-sectional studies. Finally, potentially fruitful directions for future research are presented. We suggest that it would be useful for experimental therapeutics trials to evaluate the effects of reducing the risk factors on future onset of eating pathology and on reducing maintenance factors on the risk for persistence of eating pathology, and encourage researchers to utilize prospective high-risk studies so that knowledge regarding potential intervention targets for prevention and treatment interventions for eating disorders can be advanced. Using the most rigorous research designs should help improve the efficacy of prevention and treatment interventions for eating disorders.

Single-Session Transcranial Direct Current Stimulation Temporarily Improves Symptoms, Mood, and Self-Regulatory Control in Bulimia Nervosa: A Randomised Controlled Trial

Background

Evidence suggests that pathological eating behaviours in bulimia nervosa (BN) are underpinned by alterations in reward processing and self-regulatory control, and by functional changes in neurocircuitry encompassing the dorsolateral prefrontal cortex (DLPFC). Manipulation of this region with transcranial direct current stimulation (tDCS) may therefore alleviate symptoms of the disorder.

Objective

This double-blind sham-controlled proof-of-principle trial investigated the effects of bilateral tDCS over the DLPFC in adults with BN.

Methods

Thirty-nine participants (two males) received three sessions of tDCS in a randomised and counterbalanced order: anode right/cathode left (AR/CL), anode left/cathode right (AL/CR), and sham. A battery of psychological/neurocognitive measures was completed before and after each session and the frequency of bulimic behaviours during the following 24-hours was recorded.

Results

AR/CL tDCS reduced eating disorder cognitions (indexed by the Mizes Eating Disorder Cognitions Questionnaire-Revised) when compared to AL/CR and sham tDCS. Both active conditions suppressed the self-reported urge to binge-eat and increased self-regulatory control during a temporal discounting task. Compared to sham stimulation, mood (assessed with the Profile of Mood States) improved after AR/CL but not AL/CR tDCS. Lastly, the three tDCS sessions had comparable effects on the wanting/liking of food and on bulimic behaviours during the 24 hours post-stimulation.

Conclusions

These data suggest that single-session tDCS transiently improves symptoms of BN. They also help to elucidate possible mechanisms of action and highlight the importance of selecting the optimal electrode montage. Multi-session trials are needed to determine whether tDCS has potential for development as a treatment for adult BN.

Reward and punishment sensitivity and disordered eating behaviors in men and women

BACKGROUND

Reward and punishment sensitivities have been identified as potential contributors to binge eating and compensatory behaviors, though few studies have examined gender differences in these behaviors.

METHOD

A college-aged sample (N = 1,022) completed both the Eating Disorders Diagnostic Scale (EDDS) and Sensitivity to Punishment/Sensitivity to Reward Questionnaire (SPSRQ).

RESULTS

Rates of binge eating were similar in males and females. Among those reporting compensatory behaviors, women reported engaging in compensatory behaviors more frequently than men. Sensitivity to reward and sensitivity to punishment were both positively associated with binge eating frequency in both genders. In contrast, women with high reward sensitivity reported engaging in compensatory behaviors more frequently.

CONCLUSIONS

Rates of binge eating and compensatory weight control behaviors were similar between college-aged males and females, though females who engaged in compensatory behaviors did so more frequently than males. Sensitivity to punishment was greater in females, whereas sensitivity to reward was greater in males. Reward and punishment sensitivity were each positively associated with binge eating in both males and females, while only reward sensitivity was positively associated with compensatory behaviors in females.

Dopamine-related deficit in reward learning after catecholamine depletion in unmedicated, remitted subjects with bulimia nervosa

Disturbances in reward processing have been implicated in bulimia nervosa (BN). Abnormalities in processing reward-related stimuli might be linked to dysfunctions of the catecholaminergic neurotransmitter system, but findings have been inconclusive. A powerful way to investigate the relationship between catecholaminergic function and behavior is to examine behavioral changes in response to experimental catecholamine depletion (CD). The purpose of this study was to uncover putative catecholaminergic dysfunction in remitted subjects with BN who performed a reinforcement-learning task after CD. CD was achieved by oral alpha-methyl-para-tyrosine (AMPT) in 19 unmedicated female subjects with remitted BN (rBN) and 28 demographically matched healthy female controls (HC). Sham depletion administered identical capsules containing diphenhydramine. The study design consisted of a randomized, double-blind, placebo-controlled crossover, single-site experimental trial. The main outcome measures were reward learning in a probabilistic reward task analyzed using signal-detection theory. Secondary outcome measures included self-report assessments, including the Eating Disorder Examination-Questionnaire. Relative to healthy controls, rBN subjects were characterized by blunted reward learning in the AMPT--but not in placebo--condition. Highlighting the specificity of these findings, groups did not differ in their ability to perceptually distinguish between stimuli. Increased CD-induced anhedonic (but not eating disorder) symptoms were associated with a reduced response bias toward a more frequently rewarded stimulus. In conclusion, under CD, rBN subjects showed reduced reward learning compared with healthy control subjects. These deficits uncover disturbance of the central reward processing systems in rBN related to altered brain catecholamine levels, which might reflect a trait-like deficit increasing vulnerability to BN.

From disordered eating to addiction: the "food drug" in bulimia nervosa

The high prevalence of substance abuse in individuals with bulimia nervosa (BN) and the pervasive symptom substitution in many types of drug addiction suggest that a number of substances--including food--can impair an individual's self-control, even in the presence of negative consequences. Nonetheless, the neurobiological similarities between BN and drug addiction are not clearly established. This review explores how the specific eating patterns seen in BN (binge eating and purging, with intermittent dietary restriction) are particularly addictive and differentiate BN from other eating disorders and obesity. A number of peripheral and central biological aberrations seen in BN may result in altered reward sensitivity in these individuals, particularly through effects on the dopaminergic system. Neurobiological findings support the notion that BN is an addictive disorder, which has treatment implications for therapy and pharmacological manipulations.

Empirical classification of eating disorders

Current diagnostic criteria for anorexia nervosa (AN) and bulimia nervosa (BN) account for a minority of individuals with clinically significant disorders of eating, raising concerns about the clinical utility of current definitions. This review examines evidence for the validity of current and alternative approaches to defining eating disorders and implications for draft criteria for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Although this review largely supports the predictive validity of distinctions among AN, BN, and the newly proposed binge eating disorder (BED), it also highlights that our tendency to "study what we define" has created a gap between the problems that people have and what we know about those problems. Future research on the causes and consequences of eating disorders should include more heterogeneous groups to enable identification of meaningful boundaries that distinguish between disorders based on etiological and predictive validity.

Reward abnormalities among women with full and subthreshold bulimia nervosa: a functional magnetic resonance imaging study

OBJECTIVE

To test the hypothesis that women with full and subthreshold bulimia nervosa show abnormal neural activation in response to food intake and anticipated food intake relative to healthy control women.

METHOD

Females with and without full/subthreshold bulimia nervosa recruited from the community (N = 26) underwent functional magnetic resonance imaging (fMRI) during receipt and anticipated receipt of chocolate milkshake and a tasteless control solution.

RESULTS

Women with bulimia nervosa showed trends for less activation than healthy controls in the right anterior insula in response to anticipated receipt of chocolate milkshake (vs. tasteless solution) and in the left middle frontal gyrus, right posterior insula, right precentral gyrus, and right mid dorsal insula in response to consumptions of milkshake (vs. tasteless solution).

DISCUSSION

Bulimia nervosa may be related to potential hypofunctioning of the brain reward system, which may lead these individuals to binge eat to compensate for this reward deficit, though the hypo-responsivity might be a result of a history of binge eating highly palatable foods.

Approach and avoidance motivation in eating disorders

It has been proposed that approach and avoidance processes may be critically involved in the development and maintenance of eating disorders (EDs), including anorexia nervosa (AN) and bulimia nervosa (BN). The Behavioural Inhibition System and Behavioural Activation System Scales (BIS/BAS) and Appetitive Motivation Scale (AMS) questionnaires were administered to 286 participants: 91 healthy controls (HCs), 121 participants with a current ED, either AN (restrictive and binge purge subtypes), or BN and 74 participants recovered from an ED. Individuals with EDs had higher levels of sensitivity to punishment and lower levels of reward reactivity than controls. Individuals in recovery from an ED scored the same as those in the acute group, with the exception of BAS fun seeking, for which they scored significantly higher than those with restricting AN. Discriminant analysis revealed that HCs were maximally separated from those in the acute and recovered ED groups along a dimension reflecting high punishment sensitivity and low reward sensitivity. Classification analysis demonstrated that ED and HC group membership was predicted from reward and punishment sensitivity measures; however recovered participants tended to be misclassified as ED. This study suggests high punishment sensitivity and low reward reactivity/sensitivity might form a personality cluster associated with the risk of developing an ED.

Sensitivity to reward and punishment in eating disorders

The aim of this review was to collate and summarise the self-report data regarding anomalies in sensitivity to reward and punishment in eating disorders (ED) with use of a meta-analysis where possible. Electronic databases were searched to December 2008. Studies were required to have a non-eating disorder healthy control group and include at least one self-report measure of sensitivity to reward or punishment in an eating disorder population. Findings were very heterogeneous and inconsistencies between studies and measures were highlighted. In general, patients with anorexia nervosa (restricting type) were less sensitive to reward than healthy controls, whereas patients with bulimia nervosa and anorexia nervosa (binge/purge) type were more sensitive. All ED groups report higher sensitivity to punishment than healthy controls. Individuals with eating disorders differ from healthy controls in measures of reward and punishment sensitivity as measured using the Temperament and Character Inventory, Tridimensional Personality Questionnaire and BIS/BAS scales, but further work is required as there is some heterogeneity in the data. Generating more research using behavioural measures may increase understanding of the findings.

Endophenotypes in eating disorders: moving toward etiologically based diagnosis and treatment focused on pathophysiology

It is hoped that the greater understanding neuroscience will bring to the field of psychiatry will lead to a more biologically based system of classification and diagnosis for psychiatric disorders. The clarification of endophenotypes might produce the ‘macros’ from which such a system could be constructed. The aim of this paper is to discuss the evidence for continuities between eating disorders and developmental disorders of childhood (autistic spectrum disorders and attention-deficit hyperactivity disorder) and possible shared endophenotypes. We review the evidence for obsessive–compulsive traits and disinhibition as intermediate phenotypes, and for information-processing styles such as weak set shifting, central coherence, disinhibition and reward sensitivity as possible endophenotypes. Finally we discuss the implications that this has for treatment.

High intake of palatable food predicts binge-eating independent of susceptibility to obesity: an animal model of lean vs obese binge-eating and obesity with and without binge-eating

OBJECTIVE

To determine the stability of individual differences in non-nutritive 'junk' palatable food (PF) intake in rats; assess the relationship of these differences to binge-eating characteristics and susceptibility to obesity; and evaluate the practicality of using these differences to model binge-eating and obesity.

DESIGN

Binge-eating prone (BEP) and resistant (BER) groups were identified. Differential responses to stress, hunger, macronutrient-varied PFs, a diet-induced obesity (DIO) regimen and daily vs intermittent access to a PF+chow diet, were assessed.

SUBJECTS

One hundred and twenty female Sprague-Dawley rats.

MEASUREMENTS

Reliability of intake patterns within rats; food intake and body weight after various challenges over acute (1, 2, 4 h), 24-h and 2-week periods.

RESULTS

Although BEP and BER rats did not differ in amount of chow consumed, BEPs consumed >50% more intermittent PF than BERs (P<0.001) and consistently so (alpha=0.86). BEPs suppressed chow but not PF intake when stressed, and ate as much when sated as when hungry. Conversely, BERs were more affected by stress and ate less PF, not chow, when stressed and were normally hyperphagic to energy deficit. BEP overeating generalized to other PFs varying in sucrose, fat and nutrition content. Half the rats in each group proved to be obesity prone after a no-choice high fat diet (DIO diet) but a continuous diet of PF+chow normalized the BEPs high drive for PF.

CONCLUSION

Greater intermittent intake of PF predicts binge-eating independent of susceptibility to weight gain. Daily fat consumption in a nutritious source (DIO-diet; analogous to a fatty meal) promoted overeating and weight gain but limiting fat to daily non-nutritive food (PF+chow; analogous to a snack with a low fat meal), did not. The data offer an animal model of lean and obese binge-eating, and obesity with and without binge-eating that can be used to identify the unique physiology of these groups and henceforth suggest more specifically targeted treatments for binge-eating and obesity.

The role of impulsivity in the development of substance use and eating disorders

Impulsivity is now widely viewed as a multidimensional construct consisting of a number of related dimensions. Although many measures of impulsivity are correlated, most recent factor analyses support at least a two-factor model. In the current paper, these two factors have been labelled reward sensitivity, reflecting one of the primary dimensions of Gray's personality theory, and rash-spontaneous impulsiveness. The evidence supporting the existence of two dimensions of impulsivity is reviewed in relation to substance misuse and binge eating.