Repetitive transcranial magnetic stimulation reduces cue-induced food craving in bulimic disorders

State and trait food craving in people with bulimic eating disorders

In two studies, we examined trait and state food craving levels in people with a bulimic disorder (BD) (bulimia nervosa and related disorders) and healthy controls (HC) using multidimensional self-report assessments. In study 1, trait food craving was assessed in 70 people with a BD and 69 HC using the Food Craving Questionnaire-Trait. Participants also completed the Eating Disorder Examination-Questionnaire (EDE-Q). In study 2, 45 people with a BD and 29 HC completed the Food Craving Questionnaire-State and the EDE-Q following exposure to visual and real high-caloric food cues. The results showed that both trait and state food cravings were significantly higher in people with a BD, compared to HC. Trait food craving was associated with eating disorder symptomatology in both the HC and BD groups. State food craving was associated with eating disorder psychopathology, but only in the BD group. This research underscores the importance of food craving in the study and conceptualization of BD.

Basing psychiatric classification on scientific foundation: problems and prospects

To examine whether and how the classification of mental disorders can be based on research, we evaluate the relevance of psychiatric science to the major questions in classification. We conclude that most studies cannot inform the validity of diagnostic categories because they are constrained by the classification through a top-down diagnostic approach. Analyses of relationships between diagnostic categories suggest that most interdiagnostic boundaries in current classifications lack validity. Likewise, genetic studies show that the susceptibility to mental illness is at most partly disorder-specific. Neuroimaging research is uninformative due to unsystematic single-diagnosis studies, use of super-healthy controls, and publication bias. Treatment research suggests moderate specificity in several areas of psychopathology (e.g. lithium for bipolar disorder), but lack of specificity is the rule (e.g. the broad indications of serotonin-reuptake inhibitors). In summary, evidence from multiple lines of research converges to indicate that current classifications contain excessively large numbers of categories of limited validity. Dimensional classification will not solve the problem because the number of dimensions is as uncertain as the number of categories. Psychiatric research should discard the assumption that current classification is valid. Instead of diagnosis-specific investigations, studies of unselected groups assessed with bottom-up approaches are needed to advance psychiatry.

A systematic review of non-invasive brain stimulation therapies and cardiovascular risk: implications for the treatment of major depressive disorder

Major depressive disorder (MDD) and cardiovascular diseases are intimately associated. Depression is an independent risk factor for mortality in cardiovascular samples. Neuroendocrine dysfunctions in MDD are related to an overactive hypothalamus-pituitary-adrenal (HPA) axis and increased sympathetic activity. Novel intervention strategies for MDD include the non-invasive brain stimulation (NIBS) techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). In fact, although these techniques have being increasingly used as a treatment for MDD, their cardiovascular effects were not sufficiently investigated, which would be important considering the dyad MDD/cardiovascular disorders. We investigated this issue through a systematic review for published articles from the first date available to May 2012 in MEDLINE and other databases, looking for main risk factors and surrogate markers for cardiovascular disease such as: cortisol, heart rate variability (HRV), alcohol, smoking, obesity, hypertension, glucose. We identified 37 articles (981 subjects) according to our eligibility criteria. Our main findings were that NIBS techniques might be effective strategies for down-regulating HPA activity and regulating food, alcohol, and cigarette consumption. NIBS's effects on HRV and blood pressure presented mixed findings, with studies suggesting that HRV values can decrease or remain unchanged after NIBS, while one study found that rTMS increased blood pressure levels. Also, a single study showed that glucose levels decrease after tDCS. However, most studies tested the acute effects after one single session of rTMS/tDCS; therefore further studies are necessary to investigate whether NIBS modifies cardiovascular risk factors in the long-term. In fact, considering the burden of cardiac disease, further trials in cardiovascular, depressed, and non-depressed samples using NIBS should be performed.

A debate on current eating disorder diagnoses in light of neurobiological findings: is it time for a spectrum model?

BACKGROUND

Sixty percent of eating disorders do not meet criteria for anorexia- or bulimia nervosa, as defined by the Diagnostic and Statistical Manual version 4 (DSM-IV). Instead they are diagnosed as 'eating disorders not otherwise specified' (EDNOS). Discrepancies between criteria and clinical reality currently hampering eating disorder diagnoses in the DSM-IV will be addressed by the forthcoming DSM-V. However, future diagnoses for eating disorders will rely on current advances in the fields of neuroimaging and genetics for classification of symptoms that will ultimately improve treatment.

DISCUSSION

Here we debate the classification issues, and discuss how brain imaging and genetic discoveries might be interwoven into a model of eating disorders to provide better classification and treatment. The debate concerns: a) current issues in the classification of eating disorders in the DSM-IV, b) changes proposed for DSM-V, c) neuroimaging eating disorder research and d) genetic eating disorder research.

SUMMARY

We outline a novel evidence-based 'impulse control' spectrum model of eating disorders. A model of eating disorders is proposed that will aid future diagnosis of symptoms, coinciding with contemporary suggestions by clinicians and the proposed changes due to be published in the DSM-V.

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.

Neuronal correlates of appetite regulation in patients with schizophrenia: is there a basis for future appetite dysfunction?

BACKGROUND

Given the undesired metabolic side effects of atypical antipsychotic medication it is important to understand the neuronal basis related to processing of appetite regulation in patients affected by schizophrenia.

METHODS

Here we used functional magnetic resonance imaging (fMRI) to assess brain activity in response to food cues and neutral stimuli in twenty patients with schizophrenia and eleven healthy individuals. In addition to clinical and dietary habits assessments, we collected, in patients, measurements of fasting glucose, ghrelin, leptin, insulin, prolactin and lipids blood concentration and we correlated the cerebral activity with clinical and metabolic measures.

RESULTS

Both groups engaged a common neuronal network while processing food cues, which included the left insula, primary sensorimotor areas, and inferior temporal and parietal cortices. Cerebral responses to appetitive stimuli in thalamus, parahippocampus and middle frontal gyri were specific only to schizophrenic patients, with parahippocampal activity related to hunger state and increasing linearly over time. Antipsychotic medication dosage correlated positively with a cognitive measure reflecting food cravings, whereas the severity of the disease correlated negatively with a cognitive measure indicating dietary restraint in eating habits. These cognitive variables correlated, in turn, with parahippocampal and thalamic neuronal activities, respectively.

CONCLUSIONS

We identified a specific neural substrate underlying cognitive processing of appetitive stimuli in schizophrenia, which may contribute to appetite dysfunction via perturbations in processing of homeostatic signals in relation to external stimuli. Our results also suggest that both antipsychotic medication and the disease severity per se could amplify these effects, via different mechanisms and neuronal networks.

Translational application of neuromodulation of decision-making

Recent cognitive neuroscience studies indicate that noninvasive brain stimulation can modulate a wide spectrum of behaviors in healthy individuals. Such modulation of behaviors provides novel insights into the fundamentals and neurobiology of cognitive functions in the healthy brain, but also suggests promising prospects for translational applications into clinical populations. One type of behavior that can be modulated with noninvasive brain stimulation is decision-making. For instance, brain stimulation can induce more cautious or riskier behaviors. The capacity of influencing processes involved in decision-making is of particular interest because such processes are at the core of human social and emotional functioning (or dysfunctioning). We review cognitive neuroscience studies that have successfully modulated processes involved in decision-making with transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS), including risk taking, reward seeking, impulsivity, and fairness consideration. We also discuss potential clinical relevance of these findings for patients who have still unmet therapeutic need and whose alterations in decision-making represent hallmarks of their clinical symptomatology, such as individuals with addictive disorders.

Thinking about eating food activates visual cortex with reduced bilateral cerebellar activation in females with anorexia nervosa: an fMRI study

Background

Women with anorexia nervosa (AN) have aberrant cognitions about food and altered activity in prefrontal cortical and somatosensory regions to food images. However, differential effects on the brain when thinking about eating food between healthy women and those with AN is unknown.

Methods

Functional magnetic resonance imaging (fMRI) examined neural activation when 42 women thought about eating the food shown in images: 18 with AN (11 RAN, 7 BPAN) and 24 age-matched controls (HC).

Results

Group contrasts between HC and AN revealed reduced activation in AN in the bilateral cerebellar vermis, and increased activation in the right visual cortex. Preliminary comparisons between AN subtypes and healthy controls suggest differences in cortical and limbic regions.

Conclusions

These preliminary data suggest that thinking about eating food shown in images increases visual and prefrontal cortical neural responses in females with AN, which may underlie cognitive biases towards food stimuli and ruminations about controlling food intake. Future studies are needed to explicitly test how thinking about eating activates restraint cognitions, specifically in those with restricting vs. binge-purging AN subtypes.

Subliminal food images compromise superior working memory performance in women with restricting anorexia nervosa

Prefrontal cortex (PFC) is dysregulated in women with restricting anorexia nervosa (RAN). It is not known whether appetitive non-conscious stimuli bias cognitive responses in those with RAN. Thirteen women with RAN and 20 healthy controls (HC) completed a dorsolateral PFC (DLPFC) working memory task and an anterior cingulate cortex (ACC) conflict task, while masked subliminal food, aversive and neutral images were presented. During the DLPFC task, accuracy was higher in the RAN compared to the HC group, but superior performance was compromised when subliminal food stimuli were presented: errors positively correlated with self-reported trait anxiety in the RAN group. These effects were not observed in the ACC task. Appetitive activation is intact and anxiogenic in women with RAN, and non-consciously interacts with working memory processes associated with the DLPFC. This interaction mechanism may underlie cognitive inhibition of appetitive processes that are anxiety inducing, in people with AN.

Late-life obesity is associated with smaller global and regional gray matter volumes: a voxel-based morphometric study

OBJECTIVE:

Obesity adversely affects frontal lobe brain structure and function. Here we sought to show that people who are obese versus those who are of normal weight over a 5-year period have differential global and regional brain volumes.

DESIGN:

Using voxel-based morphometry, contrasts were done between those who were recorded as being either obese or of normal weight over two time points in the 5 years prior to the brain scan. In a post-hoc preliminary analysis, we compared scores for obese and normal weight people who completed the trail-making task.

SUBJECTS:

A total of 292 subjects were examined following exclusions (for example, owing to dementia, stroke and cortical infarcts) from the Prospective Investigation of the Vasculature in Uppsala Seniors cohort with a body mass index of normal weight (<25 kg m⁻²) or obese (⩾30 kg m⁻²).

RESULTS:

People who were obese had significantly smaller total brain volumes and specifically, significantly reduced total gray matter (GM) volume (GMV) (with no difference in white matter or cerebrospinal fluid). Initial exploratory whole brain uncorrected analysis revealed that people who were obese had significantly smaller GMV in the bilateral supplementary motor area, bilateral dorsolateral prefrontal cortex (DLPFC), left inferior frontal gyrus and left postcentral gyrus. Secondary more stringent corrected analyses revealed a surviving cluster of GMV difference in the left DLPFC. Finally, post-hoc contrasts of scores on the trail-making task, which is linked to DLPFC function, revealed that obese people were significantly slower than those of normal weight.

CONCLUSION:

These findings suggest that in comparison with normal weight, people who are obese have smaller GMV, particularly in the left DLPFC. Our results may provide evidence for a potential working memory mechanism for the cognitive suppression of appetite that may lower the risk of developing obesity in later life.

Towards an animal model of food addiction

The dramatically increasing prevalence of obesity, associated with potentially life-threatening health problems, including cardiovascular diseases and type II diabetes, poses an enormous public health problem. It has been proposed that the obesity epidemic can be explained by the concept of 'food addiction'. In this review we focus on possible similarities between binge eating disorder (BED), which is highly prevalent in the obese population, and drug addiction. Indeed, both behavioral and neural similarities between addiction and BED have been demonstrated. Behavioral similarities are reflected in the overlap in DSM-IV criteria for drug addiction with the (suggested) criteria for BED and by food addiction-like behavior in animals after prolonged intermittent access to palatable food. Neural similarities include the overlap in brain regions involved in food and drug craving. Decreased dopamine D2 receptor availability in the striatum has been found in animal models of binge eating, after cocaine self-administration in animals as well as in drug addiction and obesity in humans. To further explore the neurobiological basis of food addiction, it is essential to have an animal model to test the addictive potential of palatable food. A recently developed animal model for drug addiction involves three behavioral characteristics that are based on the DSM-IV criteria: i) extremely high motivation to obtain the drug, ii) difficulty in limiting drug seeking even in periods of explicit non-availability, iii) continuation of drug-seeking despite negative consequences. Indeed, it has been shown that a subgroup of rats, after prolonged cocaine self-administration, scores positive on these three criteria. If food possesses addictive properties, then food-addicted rats should also meet these criteria while searching for and consuming food. In this review we discuss evidence from literature regarding food addiction-like behavior. We also suggest future experiments that could further contribute to our understanding of behavioral and neural commonalities and differences between obesity and drug addiction.

Unanticipated Rapid Remission of Refractory Bulimia Nervosa, during High-Dose Repetitive Transcranial Magnetic Stimulation of the Dorsomedial Prefrontal Cortex: A Case Report

A woman with severe, refractory bulimia nervosa (BN) underwent treatment for comorbid depression using repetitive transcranial magnetic stimulation (rTMS) of the dorsomedial prefrontal cortex (DMPFC) using a novel technique. Unexpectedly, she showed a rapid, dramatic remission from BN. For 5 months pre-treatment, she had reported two 5-h binge-purge episodes per day. After rTMS session 2 the episodes stopped entirely for 1 week; after session 10 there were no further recurrences. Depression scores improved more gradually to remission at session 10. Full remission from depression and binge-eating/purging episodes was sustained more than 2 months after treatment completion. In neuroimaging studies, the DMPFC is important in impulse control, and is underactive in BN. DMPFC-rTMS may have enhanced the patient's ability to deploy previously acquired strategies to avoid binge-eating and purging via a reduction in her impulsivity. A larger sham-controlled trial of DMPFC-rTMS for binge-eating and purging behavior may be warranted.

Restraint of appetite and reduced regional brain volumes in anorexia nervosa: a voxel-based morphometric study

BACKGROUND

Previous Magnetic Resonance Imaging (MRI) studies of people with anorexia nervosa (AN) have shown differences in brain structure. This study aimed to provide preliminary extensions of this data by examining how different levels of appetitive restraint impact on brain volume.

METHODS

Voxel based morphometry (VBM), corrected for total intracranial volume, age, BMI, years of education in 14 women with AN (8 RAN and 6 BPAN) and 21 women (HC) was performed. Correlations between brain volume and dietary restraint were done using Statistical Package for the Social Sciences (SPSS).

RESULTS

Increased right dorsolateral prefrontal cortex (DLPFC) and reduced right anterior insular cortex, bilateral parahippocampal gyrus, left fusiform gyrus, left cerebellum and right posterior cingulate volumes in AN compared to HC. RAN compared to BPAN had reduced left orbitofrontal cortex, right anterior insular cortex, bilateral parahippocampal gyrus and left cerebellum. Age negatively correlated with right DLPFC volume in HC but not in AN; dietary restraint and BMI predicted 57% of variance in right DLPFC volume in AN.

CONCLUSIONS

In AN, brain volume differences were found in appetitive, somatosensory and top-down control brain regions. Differences in regional GMV may be linked to levels of appetitive restraint, but whether they are state or trait is unclear. Nevertheless, these discrete brain volume differences provide candidate brain regions for further structural and functional study in people with eating disorders.

Structural magnetic resonance imaging in eating disorders: a systematic review of voxel-based morphometry studies

This systematic review summarises and critically appraises the literature on structural magnetic resonance imaging in people with a current or past eating disorder. Studies using voxel-based morphometry image analysis were included. Ten studies reported on a total of 236 people with a current or past eating disorder and 257 healthy controls. Sample heterogeneity prohibited a meta-analytic approach. The findings do not unequivocally indicate grey or white matter volume abnormalities in people with an eating disorder. Nevertheless, these preliminary data suggest that, compared with healthy controls, people with anorexia nervosa have decreased grey matter in a range of brain regions and that those with bulimia nervosa have increased grey matter volumes in frontal and ventral striatal areas. Research in the recovery phase and longitudinal studies suggest that potential brain tissue abnormalities may recover with clinical improvement. Overall, as the available data are inconclusive, further efforts in this field are warranted.

Repetitive transcranial magnetic stimulation in anorexia nervosa: a pilot study

The search for new treatments to improve outcome in people with anorexia nervosa continues. This pilot study investigated whether one session of high frequency repetitive transcranial magnetic stimulation (rTMS) delivered to the left dorsolateral prefrontal cortex reduces eating disorder related symptoms following exposure to visual and real food stimuli. Safety and tolerability were also assessed. Ten right-handed people with anorexia nervosa underwent one session of rTMS. Subjective experiences related to the eating disorder (e.g. urge to restrict, feeling full etc.) were assessed before and after rTMS. Non-parametric repeated measures tests were used. rTMS was safe and well-tolerated, and resulted in reduced levels of feeling full, feeling fat and feeling anxious. Thus, rTMS may reduce core symptoms of anorexia nervosa. Future research should establish the therapeutic potential of rTMS in anorexia nervosa.

Frontocingular dysfunction in bulimia nervosa when confronted with disease-specific stimuli

OBJECTIVE

Bulimia nervosa (BN) is characterized by dysregulation of impulse control, in other words, uncontrolled eating. Functional neuroimaging studies have been sparse and have used variable methodologies.

METHOD

Thirteen medication-free female BN patients and 13 female healthy controls were investigated by functional magnetic resonance imaging using a disease-specific food paradigm. Stimuli were rated after the scanning procedure.

RESULTS

Bulimia nervosa patients showed increased fear ratings and a trend for increased disgust. Magnetic resonance imaging data of 10 BN patients could be analysed. Three BN patients had to be excluded from the analysis because of minimal blood oxygen level dependent signals. Compared with healthy controls, BN patients showed less activation of the anterior cingulate cortex, which extended into the lateral prefrontal cortex. Furthermore, the right temporal pole showed decreased reactivity.

DISCUSSION

This study substantiates a key role of lateral prefrontal dysfunction in BN, a brain region involved in impulse control. Furthermore, the anterior cingulate cortex, which plays a key role in emotion processing, is dysfunctional. A major limitation of this study is the small sample size.

Blinding success of rTMS applied to the dorsolateral prefrontal cortex in randomised sham-controlled trials: a systematic review

OBJECTIVES

The lack of a suitable sham condition for repetitive transcranial magnetic stimulation (rTMS) research may compromise the success of blinding procedures. The aim of this systematic review was to examine the reporting of blinding success in randomised sham-controlled trials (RCTs) of rTMS applied to the dorsolateral prefrontal cortex.

METHODS

A literature search using Pubmed and Web of Science was conducted to identify RCTs of rTMS. Regression analyses were used to investigate whether participants in the real and sham rTMS groups differed in (1) their ability to correctly guess to which intervention they had been randomised, and (2) how likely they were to think they had received real rTMS.

RESULTS

Thirteen out of 96 (13.5%) RCTs reported blinding success. Available data from 9/13 studies showed that participants in real and sham rTMS groups were not significantly different in their ability to correctly guess their intervention allocation, but with a trend for participants in the real group to more often guess correctly. However, people in the real rTMS groups were significantly more likely to think they had received real rTMS compared with those in sham rTMS groups.

CONCLUSIONS

Few RCTs in rTMS report on blinding success. As current sham methods may inadequately mimic real rTMS, this could result in only partial success of blinding and bias estimations of treatment effects.

Repetitive transcranial magnetic stimulation reduces cortisol concentrations in bulimic disorders

BACKGROUND

In people with bulimic eating disorders, exposure to high-calorie foods can result in increases in food craving, raised subjective stress and salivary cortisol concentrations. This cue-induced food craving can be reduced by repetitive transcranial magnetic stimulation (rTMS). We investigated whether rTMS has a similar effect on salivary cortisol concentrations, a measure of hypothalamic-pituitary-adrenal axis (HPAA) activity.

METHOD

We enrolled twenty-two female participants who took part in a double-blind randomized sham-controlled trial on the effects of rTMS on food craving. Per group, eleven participants were randomized to the real or sham rTMS condition. The intervention consisted of one session of high-frequency rTMS delivered to the left dorsolateral prefrontal cortex (DLPFC). Salivary cortisol concentrations were assessed at four time points throughout the 90-min trial. To investigate differences in post-rTMS concentrations between the real and sham rTMS groups, a random-effects model including the pre-rTMS cortisol concentrations as covariates was used.

RESULTS

Salivary cortisol concentrations following real rTMS were significantly lower compared with those following sham rTMS. In this sample, there was also a trend for real rTMS to reduce food craving more than sham rTMS.

CONCLUSIONS

These results suggest that rTMS applied to the left DLPFC alters HPAA activity in people with a bulimic disorder.

Immediate cognitive effects of repetitive Transcranial Magnetic Stimulation in eating disorders: a pilot study

OBJECTIVE

The aim of this study was to evaluate the effects of high frequency repetitive Transcranial Magnetic Stimulation (rTMS), delivered to the dorsolateral prefrontal cortex, on selective attention in people with a bulimic disorder.

METHOD

Participants (N=33) were randomised to a single session of real or sham rTMS. They performed a Stroop colour word task before and after the rTMS intervention. Interference scores were calculated as the time difference between completing cards with congruent and incongruent stimuli.

RESULTS

Analysis of covariance comparing the interference scores post-rTMS with the pre-rTMS scores as covariates showed no differences between the real and sham groups [F(1,32)=1.110; p=0.301].

DISCUSSION

While methodological issues warrant a cautious interpretation, these pilot data suggest that selective attention is unaffected by a single session of rTMS.

Food cravings and the effects of left prefrontal repetitive transcranial magnetic stimulation using an improved sham condition

This study examined whether a single session of repetitive transcranial magnetic stimulation (rTMS) of the left prefrontal cortex (PFC) would inhibit food cravings in healthy women who endorsed frequent food cravings. Ten participants viewed images of food and completed ratings for food cravings before and after receiving either real or sham rTMS over the left PFC (10 Hz, 100% resting motor threshold, 10 s-on, 20 s-off for 15 min; 3000 pulses). Sham-TMS was matched with real TMS with respect to perceived painfulness of the stimulation. Each participant received both real and sham rTMS in random order and were blind to the condition in a within-subject cross-over design. With an improved sham control condition, prefrontal rTMS inhibited food cravings no better than sham rTMS. The mild pain from the real and sham rTMS may distract or inhibit food craving, and the decreased craving may not be caused by the effect of rTMS itself. Further studies are needed to elucidate whether rTMS has any true effects on food craving and whether painful stimuli inhibit food or other cravings. A sham condition which matches the painfulness is important to understand the true effects of TMS on behaviors and diseases.

Handedness, repetitive transcranial magnetic stimulation and bulimic disorders

Repetitive Transcranial Magnetic Stimulation (rTMS) research in psychiatry mostly excludes left-handed participants. We recruited left-handed people with a bulimic disorder and found that stimulation of the left prefrontal cortex may result in different effects in left- and right-handed people. This highlights the importance of handedness and cortex lateralisation for rTMS.

Eating disorders, gene-environment interactions and epigenetics

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