Shared and unique risk factors between lifetime purging and objective binge eating: a twin study

Threat appraisal partially mediates the relation between neuroticism and bulimic symptoms

Several studies support an association between neuroticism and bulimic symptoms; however, few studies have focused on how neuroticism exerts its influence. The purpose of this study was to extend the literature by investigating threat appraisal as a potential mediator of the relation between neuroticism and bulimic symptoms. One hundred and twenty women completed self-report measures of trait neuroticism, threat appraisal, and bulimic symptoms. Approximately half of the sample reported moderate or high levels of bulimic symptoms. Bootstrapping analyses revealed that neuroticism and threat appraisal were both positive predictors of bulimic symptoms. Further, threat appraisal partially mediated the association between neuroticism and bulimic symptoms. The findings suggest that women high in neuroticism may be vulnerable to experiencing bulimic symptoms, particularly during periods of heightened stress. These women may perceive bulimic behavior to be more effective in alleviating negative stressful emotions compared to more adaptive coping strategies. Based on the findings, women diagnosed with bulimia nervosa with high levels of neuroticism may benefit from interventions that specifically target threat appraisals to facilitate their ability to effectively adapt to stress.

Changes in disordered eating behaviors over 10 or more years: A meta-analysis

OBJECTIVE

The present meta-analysis evaluated changes in individuals' risk of engaging in distinct disordered eating behaviors (DEBs) in the long-term.

METHOD

Longitudinal studies assessing changes in DEBs via ≥2 assessments with a time lag of ≥10 years were included. Risk ratios were calculated for baseline to 10-14.9-year (M = 11.04) follow-up and baseline to ≥15-year (M = 18.62) follow-up changes in the use of binge eating, multiple purging, self-induced vomiting, laxatives, diuretics, diet pills, compensatory exercising, fasting/dieting, and multiple DEBs; Cohen's d was used for continuous binge-eating plus purging variable changes. Subgroup and meta-regression analyses tested whether eating disorder (ED) clinical sample versus nonclinical sample status, female versus male sex/gender, higher versus lower study bias, and baseline mean age and body mass index influenced overall effect magnitude for analyses with sufficient data.

RESULTS

Seventeen studies (26 [sub]samples) were included. Overall, individuals' risk of engaging in various restrictive eating and other compensatory behaviors decreased over time and the magnitudes of risk reductions for the use of certain compensatory DEBs were larger over longer follow-up durations. Specifically, for significant DEB change models, risk reductions spanned from 20.0-39.8% for 10-year follow-up and 24.7-74.8% for ≥15-year follow-up. However, nuances were found in the nature of these DEB changes as a function of DEB type, follow-up length, ED versus nonclinical sample composition, and baseline mean age.

CONCLUSIONS

These findings provide important information that can help identify treatment priorities and suggest that targeted and tailored preventative ED treatments warrant consistent implementation at the community-level, particularly for youth.

Genetic and environmental components to self-induced vomiting

OBJECTIVE

We examined the association between the genetic and environmental factors contributing to the liability to having ever engaged in self-induced vomiting (SIV initiation) and the genetic and environmental factors contributing to regular SIV behaviors (weekly or daily) for weight control.

METHOD

SIV was assessed in 3,942 women from monozygotic twin pairs and 2,790 women from same-sex dizygotic twin pairs, aged 20-47, from the Swedish Twin study of Adults: Genes and Environment. A causal-contingent-common pathway model assessed the extent to which genetic and environmental factors that influence initiation of SIV also influence regular SIV behaviors.

RESULTS

In the best-fit model, genetic and individual-specific environmental factors influenced liability to SIV initiation. The genetic factors influencing regular SIV behaviors were the same as the genetic factors influencing SIV initiation. Additional individual-specific environmental factors that were unrelated to SIV initiation influenced regular SIV behaviors.

DISCUSSION

Our findings provide evidence that the underlying liabilities for SIV initiation and regular SIV lie on the same continuum given the degree of overlap in risk between SIV initiation and regular SIV behaviors. Further, the lack of specific genetic factors and the importance of individual-specific environmental factors for regular SIV behaviors highlight the significance of environmental factors in the etiology of eating disorder symptomatology and the non-deterministic nature of genetic factors. Finally, our results suggest that when it comes to preventing individuals from developing regular SIV behavior, intervening at an environmental level is warranted.

Prevalence of and familial influences on purging disorder in a community sample of female twins

OBJECTIVE

Purging disorder (PD) was recently included as an otherwise specified feeding or eating disorder (OSFED) in the DSM-5; however, limited information is available on its prevalence, and its etiology is unknown.

METHOD

Data from 1,790 monozygotic and 1,440 dizygotic European American female twins (age range = 18-29 years) from the Missouri Adolescent Female Twin Study were used to investigate prevalence and familial influences for PD. A structured clinical interview assessed lifetime DSM-IV criteria for eating disorders and PD. After adjustment for age, twin correlations and biometrical twin models were used to estimate familial (i.e., genetic plus shared environmental) influences on PD.

RESULTS

One hundred and twenty one (3.77%; 95% CI: 3.14, 4.49) women met criteria for lifetime PD. Twin correlations suggested that genetic, shared environmental, and nonshared environmental factors influenced liability to PD. Nonshared environmental factors accounted for 56% [35%, 79%] of the variance in PD. Although familial effects accounted for a significant proportion of variance (44% [21%, 65%]), it was not possible to disentangle the independent contributions of additive genetic effects (20% [0%, 65%]) and shared environmental effects (24% [0%, 57%]).

DISCUSSION

PD is a prevalent form of eating pathology. Familial factors are relevant to the development of PD but do not demonstrate the magnitude of heritable factors found for other eating disorders.

Genetic overlap between alcohol use disorder and bulimic behaviors in European American and African American women

BACKGROUND

Despite substantial evidence that alcohol use disorder (AUD) and bulimic behaviors (i.e., binge eating and compensatory behaviors) co-occur, insufficient information exists regarding a possible shared etiology. Moreover, although numerous twin studies of European ancestry individuals have reported moderate heritability estimates for AUD and bulimic behaviors, with little evidence for shared environmental factors, research on genetic and environmental risk in African American (AA) individuals is lacking.

METHODS

We investigated specific and overlapping genetic and environmental influences on AUD and bulimic behaviors in 3232 European American (EA; 55.38% monozygotic) and 549 AA (42.81% monozygotic) young adult female twins from the Missouri Adolescent Female Twin Study (age range=18-29 years). A structured clinical interview assessed lifetime DSM-5 AUD (minus craving) and bulimic behaviors. Biometrical twin modeling was conducted to generate age-adjusted estimates of genetic and environmental influences on AUD, bulimic behaviors, and their comorbidity.

RESULTS

Estimates of genetic and environmental contributions on AUD and bulimic behaviors could be equated across EA and AA women. Additive genetic effects accounted for 59% (95% CI: 50%, 66%) and 43% (33%, 52%) of the variance in AUD and bulimic behaviors, respectively, with the remainder due to non-shared environmental effects. Shared genetic factors (rg=.33 (.18, .49)) were solely responsible for the correlation between phenotypes; the non-shared environmental correlation was not significant (re=.10 (-.05, .25)).

CONCLUSIONS

Findings indicate similar magnitudes of genetic and environmental effects on AUD and bulimic behaviors for EA and AA women and implicate common genetic mechanisms underlying liability to these problem behaviors.

Discussing the putative role of obesity-associated genes in the etiopathogenesis of eating disorders

In addition to the identification of mutations clearly related to Mendelian forms of obesity; genome-wide association studies and follow-up studies have in the last years pinpointed several loci associated with BMI. These genetic alterations are located in or near genes expressed in the hypothalamus that are involved in the regulation of eating behavior. Accordingly, it seems plausible that these SNPs, or others located in related genes, could also help develop aberrant conduct patterns that favor the establishment of eating disorders should other susceptibility factors or personality dimensions be present. However, and somewhat surprisingly, with few exceptions such as BDNF, the great majority of the genes governing these pathways remain untested in patients with anorexia nervosa, bulimia nervosa or binge-eating disorder. In the present work, we review the few existing studies, but also indications and biological concepts that point to these genes in the CNS as good candidates for association studies with eating disorder patients.

Preliminary evidence for the role of HTR2A variants in binge eating in young women

We examined the association between 15 single nucleotide polymorphisms (SNPs) in HTR2A and characteristics of disordered eating, including weight/shape concerns, binge eating (with or without loss of control), and compensatory behaviors (purging and nonpurging). Whether a lifetime history of major depressive disorder (MDD) moderated or mediated this association was also investigated. A sample of 1533 twin women of White descent that were part of the Missouri Adolescent Female Twin Study was used. Data were collected using self-report responses to a semistructured interview. Logistic regression analyses were used to examine the association between weight/shape concerns, binge eating, and compensatory behaviors and SNPs (where carriers of the minor allele were coded as 1). Two SNPs, rs6561333 and rs2296972, showed a protective influence against binge eating, with rs2296972 being significant at a trend level after application of the false discovery rate. The SNP was not associated with MDD nor did MDD moderate its putative relation with binge eating. Pending replication, our analyses provide preliminary evidence for intronic SNPs in HTR2A and their association with binge eating. Given the well-documented role of serotonergic dysfunction in eating psychopathology, this report warrants considerable further study.

Is the relationship between binge eating episodes and personality attributable to genetic factors?

Aspects of disordered eating and personality traits, such as neuroticism, are correlated and individually heritable. We examined the phenotypic correlation between binge eating episodes and indices of personality (neuroticism, extraversion, openness to experience, agreeableness, conscientiousness, and control/impulsivity). For correlations ≥|0.20|, we estimated the extent to which genetic and environmental factors contributed to this correlation. Participants included 3,446 European American same-sex female twins from the Missouri Adolescent Female Twin Study (median age = 22 years). Binge eating episode was assessed via interview questions. Personality traits were assessed by self-report questionnaires. There was a significant moderate phenotypic correlation between binge eating episode and neuroticism (r = 0.33) as well as conscientiousness (r = -0.21), while other correlations were significant but smaller (r ranging from -0.14 to 0.14). Individual differences in binge eating episodes, neuroticism, and conscientiousness were attributed to additive genetic influences (38% [95% CI: 21-53%], 45% [95% CI: 38-52%], and 44% [95% CI: 0.33-0.55%] respectively), with the remaining variance attributed to individual-specific environmental influences. Covariance was attributable to genetic (neuroticism r g = 0.37; conscientiousness r g = -0.22) and individual-specific environmental (neuroticism r e = 0.28; conscientiousness r e = -0.19) influences. Personality traits may be an early indicator of genetic vulnerability to a variety of pathological behaviors, including binge eating episode. Furthermore, prior research documenting phenotypic correlations between eating disorder diagnoses and personality may have stemmed from etiological overlap between these personality traits and aspects of disordered eating, such as binge eating episode.

Prevalence and correlates of unhealthy weight control behaviors: findings from the national longitudinal study of adolescent health

BACKGROUND

A recent study examined the prevalence, clinical correlates, age trends, and stability of unhealthy weight control behaviors (UWCB; purging and diet pill use) in a nationally representative sample of Norwegian boys and girls. The purpose of this study was to provide similar, comparative analyses for a nationally representative sample of American youth.

METHODS

Data were extracted from the restricted use data files of survey Waves I, II, and III of the National Longitudinal Study of Adolescent Health (Add Health), selecting all participants who at Wave I had provided information on age, sex, and UWCB. Using UWCB information, three groups were created (purging, diet pill use, and no recent UWCB "controls") and compared on indicators of adverse health or mental health.

RESULTS

Girls consistently were more likely than boys to report UWCB. UWCB were significantly associated with higher body mass index, self-perception of being overweight, low self-esteem, depression, and delinquency. Prevalence estimates for purging remained relatively constant across the three survey waves; in contrast, diet pill use was especially common at Wave III.

CONCLUSIONS

Age trends, gender differences, and clinical correlates of change in the likelihood of UWCB between Waves I-III were all identified in analyses comparing purging and diet pill use in American adolescents. Females and older adolescents were specifically more likely to engage in pill use than purging, and individuals with increased weight dissatisfaction, a history of delinquent behaviors, more depression symptoms, or lower self-esteem were more likely to engage in an unhealthy weight control behavior over time. While the Norwegian study found that prevalence of purging was lower among young adult participants, our results suggested that there were no significant differences in prevalence between age groups.

The genetics of eating disorders

Over the past decade, considerable advances have been made in understanding genetic influences on eating pathology. Eating disorders aggregate in families, and twin studies reveal that additive genetic factors account for approximately 40% to 60% of liability to anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Molecular genetics studies have been undertaken to identify alterations in deoxyribonucleic acid sequence and/or gene expression that may be involved in the pathogenesis of disordered eating behaviors, symptoms, and related disorders and to uncover potential genetic variants that may contribute to variability of treatment response. This article provides an in-depth review of the scientific literature on the genetics of AN, BN, and BED including extant studies, emerging hypotheses, future directions, and clinical implications.

Bulimic behaviors and alcohol use: shared genetic influences

Bulimic behaviors are frequently associated with alcohol use disorders. However, extant family and twin study findings have been inconsistent with regard to whether these behaviors share etiologic influences. A sample of 292 young adult, female twins was used to examine genetic and environmental factors underlying the association between binge eating and compensatory behaviors (e.g., vomiting)and alcohol use. Binge eating and compensatory behaviors were assessed using the Minnesota Eating Behavior Survey.Alcohol use was measured using the Alcohol Use Disorders Identification Test. Univariate models indicated that the heritability of binge eating, compensatory behaviors, and alcohol use was 41, 28, and 78%, respectively, with the remaining variance due to nonshared environmental effects.Bivariate models indicated that there was a moderate-to-large degree of overlap (genetic correlation = 0.31–0.61) in additive genetic factors between alcohol use and binge eating and compensatory behaviors, and no overlap in environmental effects. Findings suggest that these phenotypes co-aggregate in families and that similar genes or heritable traits may be contributing to their co-occurrence.

Who is really at risk? Identifying risk factors for subthreshold and full syndrome eating disorders in a high-risk sample

BACKGROUND

Numerous longitudinal studies have identified risk factors for the onset of most eating disorders (EDs). Identifying women at highest risk within a high-risk sample would allow for focusing of preventive resources and also suggests different etiologies.

METHOD

A longitudinal cohort study over 3 years in a high-risk sample of 236 college-age women randomized to the control group of a prevention trial for EDs. Potential risk factors and interactions between risk factors were assessed using the methods developed previously. Main outcome measures were time to onset of a subthreshold or full ED.

RESULTS

At the 3-year follow-up, 11.2% of participants had developed a full or partial ED. Seven of 88 potential risk factors could be classified as independent risk factors, seven as proxies, and two as overlapping factors. Critical comments about eating from teacher/coach/siblings and a history of depression were the most potent risk factors. The incidence for participants with either or both of these risk factors was 34.8% (16/46) compared to 4.2% (6/144) for participants without these risk factors, with a sensitivity of 0.75 and a specificity of 0.82.

CONCLUSIONS

Targeting preventive interventions at women with high weight and shape concerns, a history of critical comments about eating weight and shape, and a history of depression may reduce the risk for EDs.

Dietary restraint moderates genetic risk for binge eating

Dietary restraint is a prospective risk factor for the development of binge eating and bulimia nervosa. Although many women engage in dietary restraint, relatively few develop binge eating. Dietary restraint may increase susceptibility for binge eating only in individuals who are at genetic risk. Specifically, dietary restraint may be a behavioral exposure factor that activates genetic predispositions for binge eating. We investigated this possibility in 1,678 young adolescent and adult same-sex female twins from the Minnesota Twin Family Study and the Michigan State University Twin Registry. Twin moderation models were used to examine whether levels of dietary restraint moderate genetic and environmental influences on binge eating. Results indicated that genetic and nonshared environmental factors for binge eating increased at higher levels of dietary restraint. These effects were present after controlling for age, body mass index, and genetic and environmental overlap among dietary restraint and binge eating. Results suggest that dietary restraint may be most important for individuals at genetic risk for binge eating and that the combination of these factors could enhance individual differences in risk for binge eating.

Bivariate analysis of disordered eating characteristics in adolescence and young adulthood

OBJECTIVE

We examined the etiology of two disordered eating characteristics.

METHOD

Participants included 1,470 female adolescent and young adult twins and their female nontwin siblings. Phenotypic factor analyses of a seven-item eating pathology screening tool yielded two factors: weight and shape concerns and behaviors (WSCB) and binge eating (BE). Univariate and bivariate extended twin analyses (including cotwins and nontwin siblings) were used to estimate the magnitude of genetic and environmental influences on these characteristics.

RESULTS

Analyses indicated that individual differences in WSCB and BE could be explained by additive genetic influences (a² = 0.43 (95% CI: 0.33-0.52) and 0.49 (95% CI: 0.36-0.58), respectively), with the remaining variance due to nonshared environmental influences. The genetic correlation between WSCB and BE was estimated at 0.64; the nonshared environmental correlation was estimated at 0.27.

DISCUSSION

These results corroborate previous findings on genetic and environmental influences on disordered eating characteristics and suggest that findings can be extended to nontwin populations.

Specific eating disorder clusters based on social anxiety and novelty seeking

While social avoidance and distress (SAD), a key aspect of social phobia related to behavioral inhibition, is high in different eating disorders (EDs), novelty seeking (NS) is mainly linked to bulimic disorders. Since heterogeneity in NS levels (low/high) exists in social phobia and in about 55% of ED with a highly disturbed personality, we examined ED types based on SAD and NS and their relationships to eating and comorbid features. Scores of 825 ED women on SAD and NS were submitted to cluster analysis. Five clinically differentiated ED clusters emerged: two without SAD (45%) and three with high SAD and low (13%), mid (34%), high NS (8%) levels. High vs. low SAD groups showed greater eating and social impairment, ineffectiveness, ascetism, suicide attempts, and lower education. Among SAD clusters, "SAD-low NS" had the lowest rate of binge eating, vomit, substance use, stealing and compulsive buying, whereas "SAD-high NS" presented the opposite pattern. However, no differences across SAD clusters were found with regard to ED diagnostic category distribution or history of treatment. Findings show that SAD-ED types present heterogeneity of NS and greater severity.

Examination of shared risk and protective factors for overweight and disordered eating among adolescents

OBJECTIVE

To identify shared risk and protective factors for purging, binge eating, and overweight.

DESIGN

Prospective cohort study.

SETTING

Population-based questionnaires of children and adolescents residing across the United States.

PARTICIPANTS

Girls (n = 6022) and boys (n = 4518), aged 11 to 17 years in 1998, in the ongoing Growing Up Today Study.

MAIN EXPOSURES

Putative risk and protective factors within the psychological, behavioral, and socioenvironmental domains.

MAIN OUTCOME MEASURES

Overweight, use of laxatives or purging (vomiting), and binge eating. Because of the low prevalence of purging, we did not examine shared factors for this behavior among boys.

RESULTS

In 1998, a total of 219 girls (3.7%) and 30 boys (0.7%) reported purging behaviors, 426 girls (7.1%) and 90 boys (2.0%) reported binge eating, and 1019 girls (17.4%) and 1040 boys (24.6%) were overweight. From 1999 through 2001, 331 girls (7.8%) initiated purging behaviors, 503 girls (11.8%) and 132 boys (4.5%) initiated binge eating behaviors, and 424 girls (10.0%) and 382 boys (13.6%) became overweight. Concern for weight was directly associated with all 3 weight-related problems among boys and girls. Among girls, dieting, parental weight-related teasing, and family meal frequency had a shared effect on the weight-related problems examined.

CONCLUSIONS

Factors within the psychological, behavioral, and socioenvironmental domains may have a shared effect on purging, binge eating, and overweight. Further research is needed to determine if an intervention designed to address these shared risk and protective factors is effective in simultaneously reducing these weight-related problems.

The heritability of eating disorders: methods and current findings

Family, twin, and adoption studies of anorexia nervosa (AN), bulimia nervosa (BN), binge-eating disorder (BED), and the proposed purging disorder presentation (PD) have consistently demonstrated that genetic factors contribute to the variance in liability to eating disorders. In addition, endophenotypes and component phenotypes of eating disorders have been evaluated and provide further insight regarding genetic factors influencing eating disorders and eating disorder diagnostic criteria. Many of these phenotypes have demonstrated substantial heritability. This chapter reviews biometrical genetic methods and current findings from family and twin studies that investigate the role of genes and environment in the etiology of eating disorders. We review the methodology used to estimate heritability, the results of these studies, and discuss the implications of this research for the basic conceptualization of eating disorders and the future value of twin modeling in the molecular genetic era.