Psychological and weight-related characteristics of patients with anorexia nervosa-restricting type who later develop bulimia nervosa

The transition from restrictive anorexia nervosa to binging and purging: a systematic review and meta-analysis

Numerous studies addressed the topic of behavioral and symptomatic changes in eating disorders. Rates of transition vary widely across studies, ranging from 0 to 70.8%, depending on the diagnoses taken into account and the study design. Evidence shows that the specific transition from restrictive-type anorexia nervosa (AN-R) to disorders involving binging and purging behaviors (BPB) is related to a worsening of the clinical picture and worse long-term outcomes. The aim of this systematic review and meta-analysis is to focus on this specific transition, review existing literature, and summarize related risk factors. Medline and PsycINFO databases were searched, including prospective and retrospective studies on individuals with AN-R. The primary outcome considered was the rate of onset of BPB. Twelve studies (N = 725 patients) were included in the qualitative and quantitative analysis. A total of 41.84% (95% CI 33.58-50.11) of patients with AN-R manifested BPB at some point during follow-up. Risk factors for the onset of BPB included potentially treatable and untreatable factors such as the family environment, unipolar depression and higher premorbid BMI. These findings highlight that patients with AN-R frequently transition to BPB over time, with a worsening of the clinical picture. Existing studies in this field are still insufficient and heterogeneous, and further research is needed. Mental health professionals should be aware of the frequent onset of BPB in AN-R and its risk factors and take this information into account in the treatment of AN-R. LEVEL OF EVIDENCE: Evidence obtained from a systematic review and meta-analysis, Level I.

Asceticism, perfectionism and overcontrol in youth with eating disorders

PURPOSE

Personality traits such as perfectionism and asceticism, and combinations of these traits (i.e., overcontrol) have been related to eating disorder (ED) diagnosis, symptoms, and chronicity in adult patients with EDs. However, as limited evidence exists in adolescents, the aim of the present study was to examine these links in a clinical sample of adolescents with EDs.

METHOD

A retrospective chart review was conducted on 178 adolescents (91% females; M_age = 15.73 years, SD = 1.31) receiving services at a tertiary care pediatric ED program. An examination of variability in mean levels of perfectionism, asceticism, and overcontrol across ED symptom groups (restrictive and binge/purge ED subtypes) was conducted to learn of diagnostic differences, while correlations were used to explore the association of these personality traits with comorbid anxiety and depressive symptoms. Hierarchical linear regression was used to assess whether overcontrol was related to length of stay (LOS) in an inpatient program.

RESULTS

Results indicated that adolescents with binge-purge symptoms had higher levels of perfectionism, asceticism and overcontrol compared to those with restrictive symptoms, and that greater levels of perfectionism, asceticism and overcontrol were associated with elevated depression and anxiety symptoms. Additionally, overcontrol predicted greater LOS in the inpatient ED program.

CONCLUSION

Results suggest the importance of assessing, monitoring and targeting overcontrol in treatment for adolescents with EDs given its impact on comorbid symptoms and LOS.

LEVEL OF EVIDENCE

Level III, evidence obtained from case-control analytic studies.

Developmental Premorbid Body Mass Index Trajectories of Adolescents With Eating Disorders in a Longitudinal Population Cohort

OBJECTIVE

To examine whether childhood body mass index (BMI) trajectories are prospectively associated with later eating disorder (ED) diagnoses.

METHOD

Using a subsample from the Avon Longitudinal Study of Parents and Children (N = 1,502), random-coefficient growth models were used to compare premorbid BMI trajectories of individuals who later developed anorexia nervosa (n = 243), bulimia nervosa (n = 69), binge-eating disorder (n = 114), and purging disorder (n = 133) and a control group without EDs or ED symptoms (n = 966). BMI was tracked longitudinally from birth to 12.5 years of age and EDs were assessed at 14, 16, and 18 years of age.

RESULTS

Distinct developmental trajectories emerged for EDs at a young age. The average growth trajectory for individuals with later anorexia nervosa veered significantly below that of the control group before 4 years of age for girls and 2 years for boys. BMI trajectories were higher than the control trajectory for all other ED groups. Specifically, the mean bulimia nervosa trajectory veered significantly above that of controls at 2 years for girls, but boys with later bulimia nervosa did not exhibit higher BMIs. The mean binge-eating disorder and purging disorder trajectories significantly diverged from the control trajectory at no older than 6 years for girls and boys.

CONCLUSION

Premorbid metabolic factors and weight could be relevant to the etiology of ED. In anorexia nervosa, premorbid low weight could represent a key biological risk factor or early manifestation of an emerging disease process. Observing children whose BMI trajectories persistently and significantly deviate from age norms for signs and symptoms of ED could assist the identification of high-risk individuals.

A new approach to eating-disorder classification: Using empirical methods to delineate diagnostic dimensions and inform care

OBJECTIVE

Despite changes to the diagnostic criteria for eating disorders (EDs) in the DSM-5, the current diagnostic system for EDs has limited ability to inform treatment planning and predict outcomes. Our objective was to test the clinical utility of a novel dimensional approach to understanding the structure of ED psychopathology.

METHOD

Participants (N = 243; 82.2% women) were community-recruited adults with a DSM-5 ED assessed at baseline, 6-month, and 1-year follow-up. Hierarchical factor analysis was used to identify a joint hierarchical-dimensional structure of eating, mood, and anxiety symptoms. Exploratory structural equation modeling was used to test the ability of the dimensional model to predict outcomes.

RESULTS

At the top of the hierarchy, we identified a broad Internalizing factor that reflected diffuse symptoms of eating, mood, and anxiety disorders. Internalizing branched into three subfactors: distress, fear-avoidance (fears of certain stimuli and behaviors to neutralize fears, including ED behaviors designed to reduce fear of weight gain), and body dissatisfaction, which was nested within distress. The lowest level of the hierarchy was characterized by 15 factors. The hierarchical model predicted 60.1% of the variance in outcomes at 6-month follow-up, whereas all DSM eating, mood, and anxiety disorders combined predicted 35.8% of the variance in outcomes.

DISCUSSION

A dimensional approach to understanding and diagnosing EDs improved the ability to prospectively predict clinical course above-and-beyond the traditional categorical (DSM-based) approach. Our findings have implications for endeavors to improve the prediction of ED prognosis and course, and to develop more effective trans-diagnostic treatments.

Understanding eating disorders within internalizing psychopathology: A novel transdiagnostic, hierarchical-dimensional model

BACKGROUND

Several problems with the classification and diagnosis of eating disorders (EDs) have been identified, including proliferation of 'other specified' diagnoses, within-disorder heterogeneity, and frequent diagnostic migration over time. Beyond problems within EDs, past research suggested that EDs fit better in a spectrum of internalizing psychopathology (characterized by mood and anxiety disorders) than in a separate diagnostic class.

PURPOSE

To develop a transdiagnostic, hierarchical-dimensional model relevant to ED psychopathology that: 1) reduces diagnostic heterogeneity, 2) includes important dimensions of internalizing psychopathology that are often excluded from ED diagnostic models, and 3) predicts clinical impairment.

PROCEDURES

Goldberg's (2006) method and exploratory structural equation modeling were used to identify a hierarchical model of internalizing in community-recruited adults with EDs (N=207).

FINDINGS

The lowest level of the hierarchy was characterized by 15 factors that defined specific aspects of eating, mood, and anxiety disorders. At the two-factor level, Internalizing bifurcated into Distress (low well-being, body dissatisfaction, suicidality, dysphoria, ill temper, traumatic intrusions) and Fear-Avoidance (claustrophobia, social avoidance, panic symptoms, dietary restricting, excessive exercise, and compulsions). Results showed that the lowest level of the hierarchy predicted 67.7% of the variance in clinical impairment. In contrast, DSM eating, mood, and anxiety disorders combined predicted 10.6% of the variance in impairment secondary to an ED.

CONCLUSIONS

The current classification model represents an improvement over traditional nosologies for predicting clinically relevant outcomes for EDs.

Purging behaviors relate to impaired subjective sleep quality in female patients with anorexia nervosa: a prospective observational study

Background

We examined how purging behaviors relate to subjective sleep quality and sleep patterns and how symptoms of disordered eating behaviors relate to global sleep quality in female patients with anorexia nervosa (AN).

Methods

Participants were new consecutive female inpatients with a primary diagnosis of AN admitted to the Department of Psychosomatic Medicine at Kohnodai Hospital between June 26 and December 25, 2015. We recorded patients’ habitual eating behaviors, laxative overuse, or uretic misuse, and administered the Japanese versions of the Pittsburgh Sleep Quality Index (PSQI-J) and Center for Epidemiologic Studies Depression Scale. Raw PSQI-J data were used to determine sleep patterns (sleep-onset time, wake-up time, and sleep duration). To examine how purging behaviors related to sleep quality, we compared variables between AN restricting type (ANr) and AN binge-eating/purging type (ANbp). Spearman’s rank correlation analysis was used to examine which potential factors influence global PSQI-J score.

Results

Participants were 20 patients, of whom 12 had ANbp. Two ANr patients (25%) had global PSQI-J scores greater than 5, compared to 9 ANbp patients (75%; P < 0.05). Circadian rhythm disruption and abnormal sleep duration were significantly greater in ANbp patients than in ANr patients (P < 0.05). Global PSQI-J was significantly correlated with a diagnosis of ANbp (ρ = 0.525; P < 0.05), vomiting (ρ = 0.561; P < 0.05), and duration of illness (ρ = 0.536; P < 0.05).

Conclusions

ANbp patients had worse global sleep quality and greater disrupted sleep than did ANr patients. This suggests that treatments focusing on sleep would be useful, especially for ANbp patients. Furthermore, vomiting and duration of illness should be considered essential factors related to impaired global sleep quality.

Trial registration

Not applicable.

Psychometric properties of the eating disorder examination-questionnaire in Japanese adolescents

Background

Although the Eating Disorder Examination Questionnaire version 6.0 (EDE-Q) is one of the most widely used questionnaires for eating disorders in Western countries, no research has addressed the psychometric properties of the EDE-Q in a Japanese sample.

Methods

We explored the factor structure of the EDE-Q and examined the internal consistency of the derived scales for Japanese participants (Study I), the convergent validity with other eating disorder-related psychological measures (Study II) and the distinction between the derived two body image-related factors with psychological measures (StudyIII). The EDE-Q was administered to 1,430 undergraduate students in Study I and in Study II was subsequently assessed by two self-report measures of eating pathology, the Eating Attitudes Test (EAT-26) for 558 undergraduate students and the Eating Disorders Inventory-II (EDI-II) 111. In StudyIII, another 225 undergraduate students participated in an examination of the relationships of the derived body image-related subscales of the EDE-Q with the psychological measures of the Rosenberg Self-Esteem Scale, Beck Depression Inventory, Public Self-Consciousness Scale, and Multidimensional Perfectionism Scale.

Results

Exploratory factor analysis of the EDE-Q identified four meaningful factors. Of the original four EDE-Q factors, “Restriction” and “Eating Concern” were retained. However, the other two factors, “Shape” and “Weight” Concerns, were combined into two different factors: “Fear of Obesity” and “Self-Esteem Based on Shape and Weight”. Internal consistency of the derived four factors was adequate, and the relationships with EDI-II and EAT-26 measures demonstrated convergent validity. Analysis of the distinction between “Fear of Obesity” and “Self-Esteem Based on Shape and Weight” revealed that only “Self-Esteem Based on Shape and Weight” was significantly associated with the measures assessing psychopathology related to eating disorders.

Conclusions

This study describes restructured factors of the EDE-Q that were tested with undergraduate students. The distinction between two factors, “Fear of Obesity” and “Self-Esteem Based on Shape and Weight”, may further the understanding of the psychopathology of the eating disorders of adolescent Japanese subjects to facilitate future developments in research and treatment.

New Insights in Anorexia Nervosa

Anorexia nervosa (AN) is classically defined as a condition in which an abnormally low body weight is associated with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness. This article reviews recent evidences from physiology, genetics, epigenetics, and brain imaging which allow to consider AN as an abnormality of reward pathways or an attempt to preserve mental homeostasis. Special emphasis is put on ghrelino-resistance and the importance of orexigenic peptides of the lateral hypothalamus, the gut microbiota and a dysimmune disorder of neuropeptide signaling. Physiological processes, secondary to underlying, and premorbid vulnerability factors-the "pondero-nutritional-feeding basements"- are also discussed.

Retrospective Correlates for Bulimia Nervosa: A Matched Case-Control Study

OBJECTIVE

There have been few studies investigating the risk factors for bulimia nervosa (BN), and most have been in Anglo-Saxon countries. This study aimed to (i) replicate the uncontested retrospective correlates for BN and clarify the role of factors with inconsistent findings and (ii) evaluate the strength of these factors in a different culture.

METHOD

A case-control design was used to compare 60 women who met the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for BN to 60 healthy controls and 60 participants with other psychiatric disorders. Retrospective correlates were assessed by interviewing each person with the Oxford Risk Factor Interview.

RESULTS

The primary retrospective correlates identified from the comparison of BN participants to healthy controls were general high maternal expectations, negative attitudes about parental weight and obesity in childhood and adolescence. Compared with participants with other psychiatric disorders, those with BN also reported higher rates of childhood obesity, deliberate self-harm, family conflicts, general high maternal expectations and feeling fat in childhood.

CONCLUSIONS

The common findings across cultures suggest that, at least, individuals subjectively experience a number of similar factors that increase risk for developing BN. In addition, the difference regarding self-harm is notable.

Anorexia Nervosa und Bulimia Nervosa: Ein Individuationsversuch?

Zusammenfassung. Theoretischer Hintergrund: Verschiedene Theorien thematisieren Konflikte um Autonomie, Autarkie und Kontrolle in der Ätiologie von Essstörungen. Fragestellung: Diese Studie untersucht die bisher kaum empirisch überprüfte Hypothese zu einem hohen Autonomie-, Autarkie- und Kontrolle-Motiv im Zusammenhang mit Essstörungen. Methode: Insgesamt 270 ProbandInnen ohne und mit den Essstörungen Anorexia Nervosa (AN), Bulimia Nervosa (BN), Binge Eating Disorder (BED) und remittierten Essstörungen (REC) beantworteten den Fragebogen zur Analyse Motivationaler Schemata (FAMOS). Ergebnisse: ProbandInnen mit Essstörungen berichteten ein höheres Autonomie-, Autarkie- und Kontrolle-Motiv als ProbandInnen ohne Essstörungen. Außerdem zeigten sich Unterschiede in den Motiven zwischen den Essstörungsdiagnosen. Schlussfolgerungen: Die Studienergebnisse deuten auf einen Zusammenhang zwischen einem ausgeprägten Autonomie-, Autarkie- und Kontrolle-Motiv und Essstörungen hin, der für die Therapie von Essstörungen relevant sein könnte.

Ghrelin and eating disorders

There is growing evidence supporting a multifactorial etiology that includes genetic, neurochemical, and physiological components for eating disorders above and beyond the more conventional theories based on psychological and sociocultural factors. Ghrelin is one of the key gut signals associated with appetite, and the only known circulating hormone that triggers a positive energy balance by stimulating food intake. This review summarizes recent findings and several conflicting reports on ghrelin in eating disorders. Understanding these findings and inconsistencies may help in developing new methods to prevent and treat patients with these disorders.

Retrospective maternal report of early eating behaviours in anorexia nervosa

This exploratory study assessed whether maternal recall of childhood feeding and eating practices differed across anorexia nervosa (AN) subtypes. Participants were 325 women from the Genetics of Anorexia Nervosa study whose mothers completed a childhood feeding and eating questionnaire. Multinomial logistic regression analyses were used to predict AN subtype from measures related to childhood eating: (i) infant feeding (breastfed, feeding schedule, age of solid food introduction), (ii) childhood picky eating (picky eating before age 1 year and between ages one and five) and (iii) infant gastrointestinal problems (vomiting and colic). Results revealed no significant differences in retrospective maternal report of childhood feeding and eating practices among AN subtypes.

Fat mass and obesity-associated gene (FTO) in eating disorders: evidence for association of the rs9939609 obesity risk allele with bulimia nervosa and anorexia nervosa

OBJECTIVE

The common single nucleotide polymorphism (SNP) rs9939609 in the fat mass and obesity-associated gene (FTO) is associated with obesity. As genetic variants associated with weight regulation might also be implicated in the etiology of eating disorders, we evaluated whether SNP rs9939609 is associated with bulimia nervosa (BN) and anorexia nervosa (AN).

METHODS

Association of rs9939609 with BN and AN was assessed in 689 patients with AN, 477 patients with BN, 984 healthy non-population-based controls, and 3,951 population-based controls (KORA-S4). Based on the familial and premorbid occurrence of obesity in patients with BN, we hypothesized an association of the obesity risk A-allele with BN.

RESULTS

In accordance with our hypothesis, we observed evidence for association of the rs9939609 A-allele with BN when compared to the non-population-based controls (unadjusted odds ratio (OR) = 1.142, one-sided 95% confidence interval (CI) 1.001-∞; one-sided p = 0.049) and a trend in the population-based controls (OR = 1.124, one-sided 95% CI 0.932-∞; one-sided p = 0.056). Interestingly, compared to both control groups, we further detected a nominal association of the rs9939609 A-allele to AN (OR = 1.181, 95% CI 1.027-1.359, two-sided p = 0.020 or OR = 1.673, 95% CI 1.101-2.541, two-sided p = 0.015,).

CONCLUSION

Our data suggest that the obesity-predisposing FTO allele might be relevant in both AN and BN.

No association of brain-derived neurotrophic factor Val66Met polymorphism with anorexia nervosa in Japanese

The Met66 allele of the Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene has been reported to be associated with anorexia nervosa (AN), and also lower minimum body mass index (BMI) and higher harm avoidance in AN. We genotyped the Val66Met polymorphism (rs6265) in 689 AN cases and 573 control subjects. There were no significant differences in the genotype or allele frequencies of the Val66Met between AN and control subjects (allele wise, odds ratio = 0.920, 95% CI 0.785-1.079, P = 0.305). No difference was found in minimum BMIs related to Val66Met in AN (one-way ANOVA, P > 0.05). Harm avoidance scores on the Temperament and Character Inventory were lower in the Met66 allele carriers (P = 0.0074) contrary to the previous report. Thus we were unable to replicate the previous findings that the Met66 allele of the BDNF is associated with AN and that the minimum BMI is lower or the harm avoidance score is higher in AN patients with the Met66 allele.

Critical appraisal of the provisional DSM-5 criteria for anorexia nervosa and an alternative proposal

DSM-V will be highly influential in shaping conceptions and perceptions of eating disorders by the lay public, patients, and health care providers over the next 10-15 years. DSM not only influences how medical and mental health care professionals diagnose and treat patients but also impacts health insurance policies, research funding, and clinical trials. Revisions to diagnostic criteria must be carefully considered, empirically based, and consistent with current thinking both within the field and across relevant fields. Resultant criteria should be descriptive and non-judgmental and based on empirical findings without recourse to assumed etiologies. In this forum, we review problems with the current DSM IV diagnostic criteria, concerns with the proposed DSM-5 diagnostic criteria, and present an alternative classification scheme for anorexia nervosa (AN), which more accurately captures the phenomenology of the disorder and is congruent in terminology with other fields of biomedicine.

The significance of repetitive hair-pulling behaviors in eating disorders

We studied the relation between intrusive and repetitive hair pulling, the defining feature of trichotillomania, and compulsive and impulsive features in 1,453 individuals with anorexia nervosa and bulimia nervosa. We conducted a series of regression models examining the relative influence of compulsive features associated with obsessive-compulsive disorder, compulsive features associated with eating disorders, trait features related to harm avoidance, perfectionism, and novelty seeking, and self harm. A final model with a reduced sample (n = 928) examined the additional contribution of impulsive attributes. One of 20 individuals endorsed hair pulling. Evidence of a positive association with endorsement of compulsive behavior of the obsessive-compulsive spectrum emerged. Hair pulling may be more consonant with ritualistic compulsions than impulsive urges in those with eating disorders.

Investigation of factors associated to crossover from anorexia nervosa restricting type (ANR) and anorexia nervosa binge-purging type (ANBP) to bulimia nervosa and comparison of bulimia nervosa patients with or without previous ANR or ANBP

OBJECTIVE

To characterize factors associated to diagnostic crossover from anorexia nervosa restricting type (ANR) and anorexia nervosa binge-purging type (ANBP) to bulimia nervosa (BN) and to compare BN individuals with initial ANR or ANBP to subjects with stable BN.

METHOD

Two hundred thirty-eight patients with current and lifetime diagnosis of AN or BN underwent diagnostic, psychopathological, and historical examinations by means of ad hoc clinical interviews and rating scales.

RESULTS

One hundred twenty-three individuals had a stable BN. Seventy patients had a diagnosis of ANR and 45 of ANBP at the time of disease onset; 24 ANR patients and 23 ANBP subjects developed BN, whereas 46 ANR patients and 22 ANBP subjects did not crossover. Although the rate of diagnostic crossover was higher in the ANBP group than in the ANR one, the difference was not statistically significant. Longer illness duration, higher maximum past body mass index (BMI), higher novelty seeking, and lower self-directedness resulted significantly associated to crossover from ANR to BN, whereas higher maximum past BMI, higher desired body weight, higher novelty seeking, and lower harm avoidance were significantly associated to crossover from ANBP to BN. As compared to stable BN subjects, BN patients with initial ANR exhibited lower minimum past BMI, lower desired body weight, higher drive for thinness, ascetism, and social insecurity scores; BN patients with initial ANBP exhibited lower minimum past BMI and decreased enteroceptive awareness scores.

CONCLUSIONS

Different clinical and personality factors seem to be associated to crossover from ANR and ANBP to BN. Moreover, BN with initial ANR seems to differ clinically from stable BN. These findings may have therapeutic and prognostic implications.

A ghrelin gene variant may predict crossover rate from restricting-type anorexia nervosa to other phenotypes of eating disorders: a retrospective survival analysis

BACKGROUND

Patients with anorexia nervosa restricting type (AN-R) often develop bulimic symptoms and crossover to AN-binge eating/purging type (AN-BP), or to bulimia nervosa (BN). We have reported earlier that genetic variants of an orexigenic peptide ghrelin are associated with BN. Here, the relationship between a ghrelin gene variant and the rate of change from AN-R to other phenotypes of eating disorders (EDs) was investigated.

METHODS

Participants were 165 patients with ED, initially diagnosed as AN-R. The dates of their AN-R onset and changes in diagnosis to other subtypes of ED were investigated retrospectively. Ghrelin gene 3056 T-->C SNP (single nucleotide polymorphism) was genotyped. Probability and hazard ratios were analyzed using life table analysis and Cox's proportional hazard regression model, in which the starting point was the time of AN-R onset and the outcome events were the time of (i) onset of binge eating, that is, when patients changed to binge eating AN and BN and (ii) recovery of normal weight, that is, when patients changed to BN or remission.

RESULTS

Patients with the TT genotype at 3056 T-->C had a higher probability and hazard ratio for recovery of normal weight. The ghrelin SNP was not related with the onset of binge eating.

CONCLUSION

The 3056 T-->C SNP of the ghrelin gene is related to the probability and the rate of recovery of normal body weight from restricting-type AN.

Understanding the relation between anorexia nervosa and bulimia nervosa in a Swedish national twin sample

BACKGROUND

We present a bivariate twin analysis of anorexia nervosa and bulimia nervosa to determine the extent to which shared genetic and environmental factors contribute to liability to these disorders.

METHOD

Focusing on females from the Swedish Twin study of Adults: Genes and Environment (n = 7000), we calculated heritability estimates for narrow and broad anorexia nervosa and bulimia nervosa and estimated their genetic correlation.

RESULTS

In the full model, the heritability estimate for narrow anorexia nervosa (AN) was (a(2) = .57; 95% confidence interval [CI]: .00-.81) and for narrow bulimia nervosa (BN) (a(2) = .62; 95% CI: .08-.70), with the remaining variance accounted for by unique environmental factors. Shared environmental factors estimates were (c(2) = .00; 95% CI: .00-.67) for AN and (c(2) = .00; 95% CI: .00-.40) for BN. Moderate additive genetic (.46) and unique environmental (.42) correlations between AN and BN were observed. Heritability estimates for broad AN were lower (a(2) = .29; 95% CI: .04-.43) than for narrow AN, but estimates for broad BN were similar to narrow BN. The genetic correlation for broad AN and BN was .79, and the unique environmental correlation was .44.

CONCLUSIONS

We highlight the contribution of additive genetic factors to both narrow and broad AN and BN and demonstrate a moderate overlap of both genetic and unique environmental factors that influence the two conditions. Common concurrent and sequential comorbidity of AN and BN can in part be accounted for by shared genetic and environmental influences on liability although independent factors also operative.

Genetic findings in anorexia and bulimia nervosa

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

Identification of novel candidate loci for anorexia nervosa at 1q41 and 11q22 in Japanese by a genome-wide association analysis with microsatellite markers

The Japanese Genetic Research Group for Eating Disorders (JGRED) is a multisite collaborative study group that was organized for the systematic recruitment of patients with an eating disorder for the purpose of genetic study in Japan. We conducted a genome-wide case-control association study using 23 465 highly polymorphic microsatellite (MS) markers to identify genomic loci related to anorexia nervosa (AN). Pooled DNA typing in two screening stages, followed by individual typing of 320 AN cases and 341 controls, allowed us to identify 10 MS markers to be associated with AN. To narrow down genomic regions responsible for the association of these MS markers, we further conducted a single-nucleotide polymorphism (SNP) association analysis for 7 of the 10 loci in 331 AN cases and 872 controls, which include the 320 AN cases and the 341 controls genotyped in the MS screening, respectively. Two loci, namely 1q41 and 11q22, remained significantly associated with AN in the SNP-based fine mapping, indicating the success in narrowing down susceptibility regions for AN. Neither of these loci showed a positive evidence of association with bulimia nervosa. The most significant association was observed at SNP rs2048332 (allelic P-value=0.00023) located at 3'-downstream of the SPATA17 gene on the 1q41 locus. The association analysis for MS-SNP haplotypes detected a statistically significant association (permutation P-value=0.00003) of the A-4-G-T haplotype that comprised four SNP/MS markers (rs6590474-D11S0268i-rs737582-rs7947224) on the 11q22 locus with AN. This linkage disequilibrium block spanning a 20.2-kb interval contains exon 9 of the CNTN5 gene encoding contactin 5.