Genetic and environmental risk factors for the weight and shape concerns characteristic of bulimia nervosa

Mediating Mechanisms of Perfectionism: Clinical Comorbidity of OCD and ED

Obsessive-compulsive disorder (OCD) and eating disorders (ED) share common causal factors and often represent similar entities. Studies on obsessive-compulsive disorders and eating disorders reveal a significant correlation between maladaptive perfectionism. The objective of this study is to evaluate the predictive variables of perfectionism in patients diagnosed with Anorexia Nervosa (AN), Bulimia Nervosa (BN) and OCD using a structural equation model (SEM). The sample consisted of 187 participants (60.9% women, 39.1% men) with a mean age of 26.68 (SD = 10.97). The findings reveal that the model is the same in all the disorders evaluated, achieving an adequate fit: χ2 = 7.95 (p = 0.000), RMSEA = 0.087 (95% confidence interval: 0.00 to 0.02), CFI = 0.991, TLI = 0.951 and with an overall predictive capacity of around 30% (CD = 0.318). It is recommended that future studies address the subtypes of disorders evaluated using longitudinal designs.

Nutrition knowledge moderates the association between perfectionism and shape/weight concerns

Perfectionistic traits have been associated with stronger weight and diet concerns. Maladaptive perfectionism is tied to critical evaluation tendencies such as excessive concern about making mistakes, increasing one's risk for eating disorder pathology. Knowledge about healthy diet and nutrition may be one factor influencing associations between perfectionistic tendencies, as individuals with eating disorders may be more attuned to sources of nutrients. The current study examined whether nutrition knowledge moderates the association between one facet of perfectionism, concern over mistakes, and shape/weight concerns and the association between concern over mistakes and global eating pathology. College women (N = 122) completed questionnaires on disordered eating attitudes, nutrition knowledge, and perfectionism. Concern over mistakes was positively related to shape/weight concerns and global eating pathology. Nutrition knowledge significantly moderated the association between concerns over mistakes and shape/weight concerns, such that the association was stronger among those with higher levels of nutrition knowledge. Furthermore, nutrition knowledge displayed trend-level significance for the moderation of the association between concern over mistakes and global eating pathology. College women displaying high levels of concern over mistakes who are more informed about nutrition knowledge may be more vulnerable to developing concerns about body shape/weight and eating disorder pathology.

Elucidating factors underlying parent-offspring similarity in eating pathology in pre- and early puberty: Exploring the possibility of passive gene-environment correlation

Familial resemblance in eating pathology is typically attributed to parents providing an environment that leads to the development of eating pathology. However, offspring raised by biological parents receive both their environment and genes from their parents, raising the possibility that genetic influences, environmental influences, and/or gene-environment interplay may account for familial resemblance. Past studies have not explored the possibility of parents' genes influencing the environment they provide (i.e., passive gene-environment correlations or "passive rGE"). If present, passive rGE is most likely to "hide" in estimates of shared environmental influence in classical twin models. The current study used a nuclear twin family design to explore the possibility of passive rGE during pre- and early puberty when past studies have demonstrated the importance of shared environmental influence. Additionally, the present study explored whether sibling-specific (i.e., influences specific to the twin generation) or family-specific (i.e., "cultural" influences within the home) environmental influences account for shared environmental influences found in past studies. Participants included preearly pubertal same-sex female twins and their biological parents (N = 547 families) from the Minnesota Twin Family Study and the Michigan State University Twin Registry. Disordered eating was assessed with self-report measures in the twins and parents. Pubertal status was determined using an established cut-off on a self-report measure. Passive rGE was not indicated in this study of pre- and early pubertal twins. Instead, sibling-specific shared environmental and nonshared environmental influences were most influential. Future research should work to identify the sibling-specific environmental influences that contribute to sibling similarity in disordered eating. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Etiological influences on continuity and co-occurrence of eating disorders symptoms across adolescence and emerging adulthood

OBJECTIVE

The role of common and symptom-specific genetic and environmental influences in maintaining eating disorder symptoms across development remains unclear. This study investigates the continuity and change of etiological influences on drive for thinness, bulimia, and body dissatisfaction symptoms and their co-occurrence, across adolescence and emerging adulthood.

METHOD

In total, 2,629 adolescent twins (mean age = 15.20, SD = 1.95) reported eating disorders symptoms across three waves of data collection. Biometric common pathways model was fitted to estimate genetic and environmental contributions to the continuity of each symptom over time, as well as time- and symptom-specific influences.

RESULTS

Drive for thinness and body dissatisfaction symptoms showed a pattern of high continuity across development and high correlations with each other, whereas bulimia symptoms were moderately stable and less associated with the other two symptoms. Latent factors reflecting continuity of each symptom were largely under genetic influence (A_l  = 0.60-0.82). New genetic influences contributing to change in the developmental course of symptoms were observed in emerging adulthood. Genetic influences correlated considerably between the three symptoms. Non-shared environmental influences were largely time-and symptom-specific, but some contributed moderately to the continuity across development (E_l  = 0.18-0.40). The etiological overlap was larger between drive for thinness and body dissatisfaction symptoms than with bulimia symptoms.

DISCUSSION

The results provide preliminary evidence that stable as well as newly emerging genetic influences contribute to the co-occurrence of drive for thinness, bulimia, and body dissatisfaction symptoms across adolescence and emerging adulthood. Conversely, environmental influences were less stable and contributed to change in symptoms over time.

Genetic and environmental influences on thin-ideal internalization

OBJECTIVE

Current research on the etiology of thin-ideal internalization focuses on psychosocial influences (e.g., media exposure). The possibility that genetic influences also account for variance in thin-ideal internalization has never been directly examined. This study used a twin design to estimate genetic effects on thin-ideal internalization and examine if environmental influences are primarily shared or nonshared in origin.

METHOD

Participants were 343 postpubertal female twins (ages: 12-22 years; M = 17.61) from the Michigan State University Twin Registry. Thin-ideal internalization was assessed using the Sociocultural Attitudes toward Appearance Questionnaire-3.

RESULTS

Twin modeling suggested significant additive genetic and nonshared environmental influences on thin-ideal internalization. Shared environmental influences were small and non-significant.

DISCUSSION

Although prior research focused on psychosocial factors, genetic influences on thin-ideal internalization were significant and moderate in magnitude. Research is needed to investigate possible interplay between genetic and nonshared environmental factors in the development of thin-ideal internalization.

Genetic and environmental influences on disordered eating and depressive symptoms

OBJECTIVE

Research suggests that shared genetic factors underlie relationships between eating disorder and depression diagnoses, but no studies to date have examined these associations using dimensional symptom measures. This study examined whether genetic associations observed between eating disorder and depression diagnoses extend to continuous measures of these phenotypes.

METHOD

The sample consisted of 292 young adult female twins from the Michigan State University Twin Registry. Disordered eating was measured using the Minnesota Eating Behavior Survey. Depressive symptoms were assessed using the Beck Depression Inventory.

RESULTS

Univariate twin models indicated that genetic factors accounted for 55% to 60% of the variance in disordered eating and depressive symptoms, with the remaining variance accounted for by nonshared environmental effects. Bivariate models indicated that genetic factors primarily accounted for associations between disordered eating and depressive symptoms (r(a) = .70).

DISCUSSION

Phenotypic associations between disordered eating and depressive symptoms appear to be due to common genetic factors.

Undue influence of weight and shape: is it distinct from body dissatisfaction and concern about weight and shape?

BACKGROUND

Three cognitive constructs are risk factors for eating disorders: undue influence of weight and shape, concern about weight and shape, and body dissatisfaction (BD). Undue influence, a diagnostic criterion for eating disorders, is postulated to be closely associated with self-esteem whereas BD is postulated to be closely associated with body mass index (BMI). We understand less about the relationships with concern about weight and shape. The aim of the current investigation was examine the degree of overlap across these five phenotypes in terms of latent genetic and environmental risk factors in order to draw some conclusions about the similarities and differences across the three cognitive variables.

METHOD

A sample of female Australian twins (n=1056, including 348 complete pairs), mean age 35 years (S.D.=2.11, range 28-40), completed a semi-structured interview about eating pathology and self-report questionnaires. An independent pathways model was used to investigate the overlap of genetic and environmental risk factors for the five phenotypes.

RESULTS

In terms of variance that was not shared with other phenotypes, self-esteem emerged as being separate, with 100% of its variance unshared with the other phenotypes, followed by undue influence (51%) and then concern (34%), BD (28%) and BMI (32%).

CONCLUSIONS

In terms of shared genetic risk, undue influence and concern were more closely related than BD, whereas BMI and BD were found to share common sources of risk. With respect to environmental risk factors, concern, BMI and BD were more closely related to each other than to undue influence.

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.

Age differences in genetic and environmental influences on weight and shape concerns

OBJECTIVE

Previous research has shown important developmental shifts ingenetic and environmental influences for disordered eating. However, little research has examined age differences for weight/shape concerns, two key components of eating disorders. The goal of this study was to investigate these age differences in preadolescent, adolescent, young adult, and mid-adult twins.

METHOD

Participants included 2,618 female twins (ages of 10-41 years) from three large twin registries. Shape and weight concerns were assessed with the Eating Disorders Examination Questionnaire.

RESULTS

Genetic influences were modest in preadolescent twins, but significant from early-adolescence through middle adulthood. Shared environmental factors showed the opposite pattern, with the largest shared environmental contributions occurring in the youngest age group. Nonshared environmental effects remained relatively constant across age.

DISCUSSION

Findings highlight the importance of age differences in genetic and environmental influences. Possible mechanisms include gene x environment interactions and biological changes associated with key developmental stages.

A twin study of specific bulimia nervosa symptoms

BACKGROUND

Twin studies have suggested that additive genetic factors significantly contribute to liability to bulimia nervosa (BN). However, the diagnostic criteria for BN remain controversial. In this study, an item-factor model was used to examine the BN diagnostic criteria and the genetic and environmental contributions to BN in a population-based twin sample. The validity of the equal environment assumption (EEA) for BN was also tested.

METHOD

Participants were 1024 female twins (MZ n=614, DZ n=410) from the population-based Mid-Atlantic Twin Registry. BN was assessed using symptom-level (self-report) items consistent with DSM-IV and ICD-10 diagnostic criteria. Items assessing BN were included in an item-factor model. The EEA was measured by items assessing similarity of childhood and adolescent environment, which have demonstrated construct validity. Scores on the EEA factor were used to specify the degree to which twins shared environmental experiences in this model.

RESULTS

The EEA was not violated for BN. Modeling results indicated that the majority of the variance in BN was due to additive genetic factors. There was substantial variability in additive genetic and environmental contributions to specific BN symptoms. Most notably, vomiting was very strongly influenced by additive genetic factors, while other symptoms were much less heritable, including the influence of weight on self-evaluation. These results highlight the importance of assessing eating disorders at the symptom level.

CONCLUSIONS

Refinement of eating disorder phenotypes could ultimately lead to improvements in treatment and targeted prevention, by clarifying sources of variation for specific components of symptomatology.

Genetic and environmental influences on disordered eating: An adoption study

Twin studies indicate significant genetic, but little shared environmental, influences on eating disorders. However, critics argue that study limitations constrain the conclusions that can be drawn. Adoption studies avoid many of these limitations, but to date, no adoption studies of eating pathology have been conducted. The current study was the first adoption study to examine genetic/environmental effects for disordered eating. Participants included 123 adopted and 56 biological female sibling pairs. Disordered eating (i.e., overall eating pathology, body dissatisfaction, weight preoccupation, binge eating) was assessed with the Minnesota Eating Behaviors Survey (Klump, McGue, & Iacono, 2000; von Ranson, Klump, Iacono, & McGue, 2005). Biometric model fitting indicated significant genetic influences (59%-82%) on all forms of disordered eating, with nonshared environmental factors accounting for the remaining variance. Shared environmental factors did not contribute significantly to any disordered eating symptom. Our findings bolster those from twin studies and provide critical evidence of significant genetic effects on disordered eating symptoms.

Do weight and shape concerns exhibit genetic effects? Investigating discrepant findings

OBJECTIVE

Unlike twin studies of general weight and shape concerns, studies examining the heritability of the undue influence of weight and shape concerns on self-evaluation have found little evidence for genetic effects. The present study sought to resolve these discrepancies by examining the heritability of both types of weight and shape concerns in a young adult twin sample.

METHOD

Participants included 270 female twins from the Michigan State University Twin Registry. General weight and shape concerns were assessed with subscales from the Eating Disorder Examination Questionnaire (EDEQ). Similar to previous research, the undue influence of weight and shape on self-evaluation was assessed using averaged scores from two EDEQ items.

RESULTS

The heritability of all weight and shape measures was estimated at 49-66%.

DISCUSSION

General weight and shape concerns and the undue influence of these concerns on self-evaluation are influenced by genetic factors in young adult female twins.

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.

Should non-fat-phobic anorexia nervosa be included in DSM-V?

OBJECTIVE

Cross-cultural data suggest that rationales for food refusal vary in anorexia nervosa (AN), and a variant, termed non-fat-phobic AN (NFP-AN), has been described. This review evaluates whether data support modification of the requirement for intense fear of weight gain to meet AN criterion B in DSM-V.

METHOD

We performed a systematic search of the Medline and PsychInfo literature and evaluated the relevant publications by Robins and Guze's (Am J Psychiatry 126, 983-987, 1970) criteria as a standard for diagnostic validity. We also performed a meta-analysis comparing the severity of eating pathology in AN to (a) NFP-AN and (b) AN with low drive for thinness (low-DT-AN).

RESULTS

A modest literature indicates that NFP-AN has wide geographic distribution and occurs in both Western and non-Western populations alongside cases of typical AN. Aggregating across eligible studies, patients with NFP-AN or low-DT-AN score at least 2/3 of a standard deviation lower on measures of eating pathology than patients with conventional AN. Transcultural comparison of drive for thinness suggests significantly lower norms in non-Western cultures.

DISCUSSION

NFP-AN occurs with wide distribution. Further research is necessary on the course and outcomes of NFP-AN to characterize its congruence with, or distinction from, conventional AN. We discuss several options for including a description of NFP-AN in DSM-V.

New insights into symptoms and neurocircuit function of anorexia nervosa

Individuals with anorexia nervosa have a relentless preoccupation with dieting and weight loss that results in severe emaciation and sometimes death. It is controversial whether such symptoms are secondary to psychosocial influences, are a consequence of obsessions and anxiety or reflect a primary disturbance of brain appetitive circuits. New brain imaging technology provides insights into ventral and dorsal neural circuit dysfunction - perhaps related to altered serotonin and dopamine metabolism - that contributes to the puzzling symptoms found in people with eating disorders. For example, altered insula activity could explain interoceptive dysfunction, and altered striatal activity might shed light on altered reward modulation in people with anorexia nervosa.

Assessing the heritability of anorexia nervosa symptoms using a marginal maximal likelihood approach

BACKGROUND

Assessment of eating disorders at the symptom level can facilitate the refinement of phenotypes. We examined genetic and environmental contributions to liability to anorexia nervosa (AN) symptoms in a population-based twin sample using a genetic common pathway model.

METHOD

Participants were from the Norwegian Institute of Public Health Twin Panel (NIPHTP) and included all female monozygotic (MZ; 448 complete pairs and four singletons) and dizygotic (DZ; 263 complete pairs and four singletons) twins who completed the Composite International Diagnostic Interview (CIDI) assessing DSM-IV Axis I and ICD-10 criteria. Responses to items assessing AN symptoms were included in a model fitted using the marginal maximum likelihood (MML) approach.

RESULTS

Heritability of the overall AN diagnosis was moderate [a2=0.22, 95% confidence interval (CI) 0.0-0.50] whereas heritabilities of the specific items varied. Heritability estimates for weight loss items were moderate (a2=0.31-0.34) and items assessing weight concern when at a low weight were smaller (0.18-0.29). Additive genetic factors contributed little to the variance of amenorrhea, which was most strongly influenced by unshared environment (a2=0.16, e2=0.71).

CONCLUSIONS

AN symptoms are differentially heritable. Specific criteria such as those related to body weight and weight loss history represent more biologically driven potential endophenotypes or liability indices. The results regarding weight concern differ somewhat from those of previous studies, highlighting the importance of assessing genetic and environmental influences on variance of traits within specific subgroups of interest.

Environmental and genetic risk factors for eating disorders: What the clinician needs to know

Patients and families often are aware of research on genetic factors influencing eating disorders. Accurate interpretations of research on environmental and genetic risk factors can be empowering to patients and families; however, misinterpretations could prove detrimental. Clinicians who are not versed in genetic research may believe they are ill prepared to discuss the nuances of genetic research with patients and families. In this article the authors discuss what is known about genetic and environmental risk factors with an emphasis on gene-environment interplay to improve clinicians' comfort level in discussing these complex issues with their patients.

Genetic influences on disordered eating behaviour are largely independent of body mass index

OBJECTIVE

Prior studies suggest eating disorders and related characteristics are moderately to substantially heritable. We are interested in identifying the genes underlying disordered eating behaviour (DEB), and want to know how much of the genetic influence underlying DEB is attributable to genetic influences on body mass index (BMI).

METHOD

Bivariate analyses were performed, in adolescent twins and siblings, to estimate the genetic and environmental contributions for DEB, BMI, and their overlap.

RESULTS

Shared genetic risk factors explained the overlap between BMI and DEB (genetic correlation was 0.43 in women, 0.51 in men). DEB was highly heritable in women (a(2) = 0.65; a(2) independent of BMI = 0.53) and moderately heritable in men (a(2) = 0.39; a(2) independent of BMI = 0.29). BMI was highly heritable in both men (a(2) = 0.76) and women (a(2) = 0.80).

CONCLUSION

The entire correlation between DEB and BMI was explained by shared genetic risk, but the majority of genetic influences on DEB were due to genetic effects independent of BMI.

Genetic epidemiology, endophenotypes, and eating disorder classification

OBJECTIVE

To explore how genetic epidemiology has informed the identification of endophenotypes and how endophenotypes may inform future classification of eating disorders.

METHOD

Literature review and synthesis.

RESULTS

Although a number of endo- and subphenotypes have been suggested for eating disorders, few reach the rigorous definitions developed for candidate endophenotypes.

CONCLUSION

Further study of endophenotypes and subphenotypes for eating disorders may assist with developing a more homogenous classification system that more closely reflects underlying biological mechanisms, and provides a clearer focus for the development of coherent models and treatments.

A transdiagnostic approach to understanding eating disorders

Categorical models dominate the eating disorder field, but the tandem use of categorical and dimensional models has been proposed. A transdiagnostic dimensional model, number of lifetime eating disorder behaviors (LEDB), was examined with respect to (1) its relationship to a variety of indicators of the individual's functioning, (2) the degree to which it was influenced by genetic and environmental risk factors, and (3) exposure to specific environmental risk factors. Data from self-report and interview from 1002 female twins (mean age = 34.91 years, SD = 2.09) were examined. While 15.4% women met criteria for a lifetime eating disorder, 29% had at least one LEDB. The dimensional measure provided an indicator of associated functioning, and was influenced primarily by the nonshared environment. The number of LEDB was associated with the degree of impaired functioning. This impairment was associated with conflict between parents and criticism from parents when growing up.

Gender differences in associations of eating pathology between mothers and their adolescent offspring

OBJECTIVE

To study the association of eating pathology between mothers and their adolescent offspring in a population sample.

RESEARCH METHODS AND PROCEDURES

The participants were 481 women (mean age, 47+/-SD 5 years; BMI, 25+/-4 kg/m2) and their 481 adolescent children 16 to 17 years old (BMI, 21+/-3 kg/m2) of the Stockholm Weight Development Study. Assessment methods were the Three-Factor Eating Questionnaire Revised 18 and the Eating Disorder Inventory 2.

RESULTS

A higher body weight was most related to cognitive restraint for adolescents and to emotional eating for adult women. A mother-daughter link could be identified for eating pathology, with the strongest link found for emotional eating. No mother-son link could be identified. Age subgroup analyses revealed a stronger mother-daughter link for body attitudes in younger mothers and for cognitive restraint in older mothers.

DISCUSSION

Gender differences revealed that eating pathology was shared by mothers and daughters but not by mothers and sons. A psychological strategy such as eating as a response to negative emotions was most interrelated between mothers and daughters. Younger mothers shared more attitudes toward the body with their daughters, whereas older mothers shared more restrictive eating behaviors with their daughters. The mother-daughter links found may be due to gender-specific genetic and psychological family transmission and gender-specific environmental influences. The sons' eating behaviors seem to be more independent and would be formed by other factors than for the girls.

Influence of heredity on dietary restraint, disinhibition, and perceived hunger in humans

OBJECTIVE

Dietary restraint, disinhibition, and perceived hunger have been shown to affect food intake and body weight and are thought to be risk factors for eating disorders, but little is known about their origins. We investigated the influence of heredity, shared (familial) environment, and individual environment on dietary restraint disinhibition, perceived hunger and their relation to body size and food intake.

METHODS

Scores on the Three Factor Eating Questionnaire and the Restraint Scale in addition to height, weight, body mass index, and 7-d diary reported nutrient intakes were obtained from 39 identical, 60 fraternal same-sex, and 50 fraternal opposite-sex adult twin pairs who were living independently. Linear structural modeling was applied to investigate the nature and degree of genetic and environmental influences.

RESULTS

Analysis showed significant genetic and individual environmental, but not shared (familial) environmental, influences on cognitive restraint, perceived hunger, and Restraint Scale scores, with genes accounting for 44%, 24%, and 58% of the variance, respectively. In contrast, disinhibition was found to be significantly influenced by the shared (familial) environment, accounting for 40% of the variance. Further analysis showed that cognitive restraint and perceived hunger heritabilities could not be accounted for by significant heritabilities of body weight, height, or body mass index. In contrast, the heritability of Restraint Scale scores was found to be related to body size. Cognitive restraint was negatively correlated with nutrient intake, and differences in cognitive restraint were found to be related to differences in the body sizes of identical twin pairs.

CONCLUSIONS

Dietary restraint appears to be another component in a package of genetically determined physiologic, sociocultural, and psychological processes that regulate energy balance, whereas dietary disinhibition may be the intermediary between upbringing and the development of overweight and/or eating disorders.

Body dissatisfaction and drive for thinness in young adult twins

OBJECTIVE

We explored correlates of the Eating Disorder Inventory subscales Body Dissatisfaction (BD) and Drive for Thinness (DT) and genetic and environmental influences on these traits.

METHOD

In a population-based sample of 4,667 Finnish twins aged 22-27 years, we conducted twin modeling to explore genetic and environmental contributions to body dissatisfaction and drive for thinness. Logistic regression was used for the correlational analysis.

RESULTS

Various eating and body size-related factors and psychosomatic symptoms were significantly associated with high body dissatisfaction and drive for thinness in both genders. In women, early puberty onset, early initiation of sexual activity, and multiple sex partners were statistically significant risk factors of body dissatisfaction. In gender-specific univariate twin models, additive genes accounted for 59.4% (95% confidence interval [CI] = 53.2-64.7%) of the variance in body dissatisfaction and for 51.0% (95% CI = 43.7-57.5%) of the variance in drive for thinness among females, but for none of the variance among males.

DISCUSSION

There are very distinct gender differences in the heritability patterns of body dissatisfaction and drive for thinness in young adults.

Genetic analysis of bulimia nervosa: methods and sample description

OBJECTIVE

Twin and family studies suggest that genetic variants contribute to the pathogenesis of bulimia nervosa (BN) and anorexia nervosa (AN). The Price Foundation has supported an international, multisite study of families with these disorders to identify these genetic variations. The current study presents the clinical characteristics of this sample as well as a description of the study methodology.

METHOD

All probands met modified criteria for BN or bulimia nervosa with a history of AN (BAN) as defined in the 4th ed. of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994). All affected relatives met DSM-IV criteria for BN, AN, BAN, or eating disorders not otherwise specified (EDNOS). Probands and affected relatives were assessed diagnostically using both trained-rater and self-report assessments. DNA samples were collected from probands, affected relatives, and available biologic parents.

RESULTS

Assessments were obtained from 163 BN probands and 165 BAN probands. Overall, there were 365 relative pairs available for linkage analysis. Of the affected relatives of BN probands, 62 were diagnosed as BN (34.8%), 49 as BAN (27.5%), 35 as AN (19.7%), and 32 as EDNOS (18.0%). For the relatives of BAN probands, 42 were diagnosed as BN (22.5%), 67 as BAN (35.8%), 48 as AN (25.7%), and 30 as EDNOS (16.0%).

DISCUSSION

This study represents the largest genetic study of eating disorders to date. Clinical data indicate that although there are a large number of individuals with BN disorders, a range of eating pathology is represented in the sample, allowing for the examination of several different phenotypes in molecular genetic analyses.

Undue influence of weight on self-evaluation: a population-based twin study of gender differences

OBJECTIVE

To explore the extent to which genetic and environmental factors contribute to liability to placing undue importance on weight as an indicator of self-evaluation and to determine whether differences exist across genders in the nature and magnitude of these effects.

METHOD

Self-report data were collected on 8,045 same-sex and opposite-sex twins, aged 18-31 years, from a population-based registry of Norwegian twins. Structural equation modeling was utilized to estimate the relative contribution of genetic and environmental factors to liability for undue influence of weight on self-evaluation, allowing for gender-specific effects.

RESULTS

Individual variation in undue influence of weight on self-evaluation was best explained by shared and individual environmental influences. No significant gender differences were found. Shared environmental factors accounted for 31% of the variance.

DISCUSSION

These results raise the possibility that there may be distinct sources of familial resemblance for different symptoms of bulimia nervosa as codified in the 4th ed. of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994).

A Biopsychosocial Model of Disordered Eating and the Pursuit of Muscularity in Adolescent Boys

This review provides an evaluation of the correlates and/or risk factors associated with disordered eating and the pursuit of muscularity among adolescent boys. One of the main conclusions is that similar factors and processes are associated with both behavioral problems. Several factors found to be consistently associated with disordered eating among boys are also similar to those found with girls. These include body mass index, negative affect, self-esteem, perfectionism, drug use, perceived pressure to lose weight from parents and peers, and participation in sports that focus on leanness. However, as many of the findings have only been verified using cross-sectional designs, prospective studies are now needed.

Coming to Terms With Risk Factors for Eating Disorders: Application of Risk Terminology and Suggestions for a General Taxonomy

The aims of the present review are to apply a recent risk factor approach (H. C. Kraemer et al., 1997) to putative risk factors for eating disorders, to order these along a timeline, and to deduce general taxonomic questions. Putative risk factors were classified according to risk factor type, outcome (anorexia nervosa, bulimia nervosa, binge-eating disorder, full vs. partial syndromes), and additional factor characteristics (specificity, potency, need for replication). Few of the putative risk factors were reported to precede the onset of the disorder. Many factors were general risk factors; only few differentiated between the 3 eating disorder syndromes. Common risk factors from longitudinal and cross-sectional studies were gender, ethnicity, early childhood eating and gastrointestinal problems, elevated weight and shape concerns, negative self-evaluation, sexual abuse and other adverse experiences, and general psychiatric morbidity. Suggestions are made for the conceptualization of future risk factor studies.

Gender differences in binge-eating: a population-based twin study

OBJECTIVE

To assess whether genetic and environmental effects on liability to binge-eating (BE) are of equal importance for males and females and whether the same genetic risk factors predispose to BE in the two sexes.

METHOD

Questionnaire data on 8045 same sex and opposite sex twins, aged 19-31 years, from a population-based Norwegian registry, was used to estimate the relative contribution of genetic and environmental factors to liability for BE utilizing structural equation modeling.

RESULTS

In the best-fitting model, the magnitude of genetic and environmental effects on BE was the same for males and females. Heritability was 51%. The correlation between genetic risk factors in men and women was estimated to be +0.57.

CONCLUSION

Binge-eating appears to be equally heritable in males and females. Although the majority of the genetic risk factors are shared between the sexes, there may exist gender-specific genetic effects on liability.

Dieting, body weight, body image and self-esteem in young women: doctors' dilemmas

Many young women feel that body image and exercise are important for their self-esteem, want to lose weight, are afraid they might gain weight, and feel fat. Interventions that improve self-esteem, encourage communication and help adolescents to be supportive of each other may prevent some of these women from developing eating disorders. If an eating disorder is suspected, it may be useful for physicians to ask about fear of loss of control over the body, eating, weight and shape; and preoccupation with food, eating, nutrition, body weight and shape, as these issues may differentiate those at greater risk.

Differential heritability of eating attitudes and behaviors in prepubertal versus pubertal twins

OBJECTIVE

Differential heritability of eating pathology in prepubertal, pubertal, and 17-year-old twins was examined using a population-based twin sample.

METHOD

Participants included 530 11-year-old (452 prepubertal, 78 pubertal twins) and 602 17-year-old female twins from the Minnesota Twin Family Study. Puberty was assessed with the Pubertal Development Scale, and general eating pathology was assessed with the total score from the Minnesota Eating Disorders Inventory (M-EDI).

RESULTS

M-EDI total score intraclass correlations for the pubertal 11-year-old group were more similar to the 17-year-old twins' than the prepubertal 11-year-old twins, suggesting similar levels of genetic influence in the pubertal and older adolescent cohort. Model-fitting corroborated these impressions, indicating that genetic factors accounted for 0% of the variance in 11-year-old prepubertal twins but 54% of the variance in 11-year-old pubertal and 17-year-old twins.

DISCUSSION

Findings suggest that a portion of the genetic influence on eating pathology may become activated during puberty.

Structural modeling analysis of prospective risk factors for eating disorder

Many variables have been suggested as possible risk factors for eating disorders (ED), although the validity of these suggestions has seldom been tested causally. The current study tested a pathway model for the development of ED using prospective data from a randomly selected sample of 807 women, aged 18-32 years, from the general population of Sweden. Data was collected using self-report questionnaires with well-established psychometric properties. The cardinal symptoms of binge eating, purging, and fear of weight gain according to the DSM-IV characterized ED. Data supported the hypothesized model suggesting that low self-esteem, low perceived social support from the family, high levels of body concern, and high relative use of escape avoidance coping constitute a risk profile for later development of ED. Given the results and the fact that these risk factors can be modified, their practical utility and clinical significance should be examined in prevention studies.

Genetic relationships between personality and eating attitudes and behaviors

Genetic and environmental factors underlying relationships between personality traits and disordered eating were examined in 256 female adolescent twin pairs (166 monozygotic, 90 dizygotic). Eating behaviors were assessed with the Total Score, Body Dissatisfaction, Weight Preoccupation, Binge Eating, and Compensatory Behavior subscales from the Minnesota Eating Disorders Inventory (M-EDI; K. L. Klump, M. McGue, & W. G. Iacono, 2000). Personality characteristics were assessed with the Negative Emotionality, Positive Emotionality, and Constraint scales from the Multidimensional Personality Questionnaire (MPQ; A. Tellegen, 1982). Model-fitting analyses indicated that although genetic factors were more likely to contribute to MPQ and M-EDI phenotypic associations than environmental factors, shared genetic variance between the 2 phenotypes was limited. MPQ personality characteristics may represent only some of several genetic risk factors for eating pathology.

Does environment matter? A review of nonshared environment and eating disorders

OBJECTIVE

Nonshared environmental influences are experiences that are unique to siblings reared in the same family. We review studies highlighting the importance of nonshared factors for the development of eating disorders and suggest areas for future research.

METHODS

Findings from behavioral genetic studies of eating disorders as well as methodological issues are reviewed.

RESULTS

Twin studies suggest that approximately 17%-46% of the variance in both anorexia nervosa (AN) and bulimia nervosa (BN) can be accounted for by nonshared environmental factors. Studies directly examining these influences are scarce, although initial data indicate that differential paternal relationships, body weight teasing, peer group experiences, and life events may account for the development of eating pathology in one sibling versus another.

DISCUSSION

Additional research is needed to identify specific nonshared environmental influences on eating disorders such as differential parental and sibling treatment, disparate peer group characteristics, and differential experience of life events such as physical and sexual abuse.

The children of mothers with eating disorders

There is good evidence that children of parents with psychological disorders are themselves at increased risk of disturbances in their development. Although there has been considerable research on a variety of disorders such as depression and alcohol, research on the children of parents with eating disorders has been relatively recent. This paper aims to review the evidence and covers a number of areas, including genetic factors, pregnancy, the perinatal and postpartum period, infancy, and the early years of life, focusing on feeding and mealtimes, general parenting functions, and growth. This is followed by a consideration of psychopathology in the children, parental attitudes to children's weight and shape, and adolescence. What is clear is that although there are numerous case reports and case series, the number of systematic controlled studies is relatively small, and almost nothing has been written about the children of fathers with eating disorders. What is evident from the available evidence is that children of mothers with eating disorders are at increased risk of disturbance, but that the risk depends on a variety of factors, and that difficulties in the children are far from invariable. The paper concludes by summarizing five broad categories of putative mechanisms, based on the evidence to date, by which eating disturbance in parents can influence child development.

Investigation of quality of the parental relationship as a risk factor for subclinical bulimia nervosa

OBJECTIVE

Previous literature suggests a link between the quality of the parental relationship and disordered eating in offspring. We investigated the relationship between offspring pyschopathology and the parental relationship using a population-based twin registry that contained 766 complete twin pairs.

METHOD

We used reports of twin lifetime psychopathology from the twins and quality of parental relationship and parental lifetime psychopathology from both parents.

RESULTS

Poorer quality of the marital relationship predicted the presence of subclinical bulimia nervosa (SBN) using both mother's (odds ratio [OR] = 0.83, 95% confidence interval [CI]: 0.71-0.97) and father's (OR = 0.78, 95% CI: 0.62-0.97) reports. It also predicted the presence of generalized anxiety disorder (GAD) and alcohol dependence. SBN was still strongly predicted by the marital relationship when parental psychopathology was included as a covariate.

DISCUSSION

These results are supportive of the notion that a conflictual and distant marital relationship can, at least partially, act as an environmental risk factor for SBN.

Development of weight and shape concerns in the aetiology of eating disorders

BACKGROUND

Although weight and shape concerns are considered to be integral to the psychopathology of anorexia and bulimia nervosa, uncertainties remain about developmental aspects of the aetiology of these concerns and their relationship to eating disorders.

AIMS

To review the recent literature on weight and shape concern, with particular emphasis on aetiology, to identify a possible developmental pathway from weight concern through abnormal eating behaviour to disorder.

METHOD

Literature review of Medline and Psychlit databases using the keywords 'eating disorder', 'weight concern', 'shape concern' and 'aetiology'. Inclusion criteria were based on the strength of quantitative research findings, originality of ideas and recent publication.

RESULTS

Weight and shape concerns follow a developmental pathway arising before the typical age for the development of eating disorders. The origins are multifactorial, with biological, family and sociocultural features predominating.

CONCLUSIONS

Although weight and shape concern seems commonly to underlie the development of eating disorders, an alternative pathway appears to exist through impulsivity and fear of loss of control. Prevention strategies may usefully focus on the attitudes and concerns that lead to dieting behaviour.

The evolving genetic foundations of eating disorders

Data described earlier are clear in establishing a role for genes in the development of eating abnormalities. Estimates from the most rigorous studies suggest that more than 50% of the variance in eating disorders and disordered eating behaviors can be accounted for by genetic effects. These high estimates indicate a need for studies identifying the specific genes contributing to this large proportion of variance. Twin and family studies suggest that several heritable characteristics that are commonly comorbid with AN and BN may share genetic transmission with these disorders, including anxiety disorders or traits, body weight, and possibly major depression. Moreover, some developmental research suggests that the genes involved in ovarian hormones or the genes that these steroids affect also may be genetically linked to eating abnormalities. Molecular genetic research of these disorders is in its infant stages. However, promising areas for future research have already been identified (e.g., 5-HT2A receptor gene, UCP-2/UCP-3 gene, and estrogen receptor beta gene), and several large-scale linkage and association studies are underway. These studies likely will provide invaluable information regarding the appropriate phenotypes to be included in genetic studies and the genes with the most influence on the development of these disorders.

Characteristics of monozygotic twins discordant for bulimia nervosa

OBJECTIVE

We studied monozygotic (MZ) twins who were discordant for bulimia nervosa in order to identify environmental factors that could have contributed to the expression of bulimia nervosa in only one member of these genetically identical twin pairs.

METHOD

Female twin pairs from the Virginia Twin Registry were identified. One twin met DSM-III-R criteria for bulimia nervosa (excluding the frequency and duration criterion) and the co-twin either reported some symptoms of bulimia nervosa but never met full diagnostic criteria (n = 20 pairs) or reported no symptoms of bulimia nervosa (n = 10). We compared the twins on demographic, developmental, personality, and psychiatric dimensions using self- and maternal report.

RESULTS

Affected twins were more likely to report lifetime generalized anxiety disorder and were described by their mothers as more anxious and fearful as children. They also had significantly lower mastery, optimism, and self-esteem, and significantly greater obsessive and compulsive symptoms than their unaffected co-twins. Affected twins recalled greater discord in their families but viewed their parents as more warm toward them than toward their unaffected co-twin.

DISCUSSION

Given that MZ twins are genetically identical and share a common family background, differences between them must be attributable to unique environmental factors. Although it is difficult to disentangle predisposing risk factors from sequelae of psychiatric illness in a retrospective co-twin control design, the affected twins were perceived to have been more anxious as children by their mothers-possibly reflecting a predisposing trait. More extensive interviews are required to determine the nature of environmental events that contribute to the expression of the observed personality, behavioral, anxious, and eating-related traits in the affected twins.

A search for susceptibility loci for anorexia nervosa: methods and sample description

BACKGROUND

Eating disorders have not traditionally been viewed as heritable illnesses; however, recent family and twin studies lend credence to the potential role of genetic transmission. The Price Foundation funded an international, multisite study to identify genetic factors contributing to the pathogenesis of anorexia nervosa (AN) by recruiting affective relative pairs. This article is an overview of study methods and the clinical characteristics of the sample.

METHODS

All probands met modified DSM-IV criteria for AN; all affected first, second, and third degree relatives met DSM-IV criteria for AN, bulimia nervosa (BN), or eating disorder not otherwise specified (NOS). Probands and affected relatives were assessed diagnostically with the Structured Interview for Anorexia and Bulimia. DNA was collected from probands, affected relatives and a subset of their biological parents.

RESULTS

Assessments were obtained from 196 probands and 237 affected relatives, over 98% of whom are of Caucasian ancestry. Overall, there were 229 relative pairs who were informative for linkage analysis. Of the proband-relative pairs, 63% were AN-AN, 20% were AN-BN, and 16% were AN-NOS. For family-based association analyses, DNA has been collected from both biological parents of 159 eating-disordered subjects. Few significant differences in demographic characteristics were found between proband and relative groups.

CONCLUSIONS

The present study represents the first large-scale molecular genetic investigation of AN. Our successful recruitment of over 500 subjects, consisting of affected probands, affected relatives, and their biological parents, will provide the basis to investigate genetic transmission of eating disorders via a genome scan and assessment of candidate genes.

Twin studies of eating disorders: a review

OBJECTIVE

Twin methodology has been used to delineate etiological factors in many medical disorders and behavioral traits including eating disorders. Although twin studies are powerful tools, their methodology can be arcane and their implications easily misinterpreted.

METHOD

The goals of this study are to (a) review the theoretical rationale for twin studies; (b) provide a framework for their interpretation and evaluation; (c) review extant twin studies on eating disorders; and (d) explore the implications for understanding etiological issues in eating disorders.

DISCUSSION

On the basis of this review, it is not possible to draw firm conclusions regarding the precise contribution of genetic and environmental factors to anorexia nervosa. Twin studies confirm that bulimia nervosa is familial and reveal significant contributions of additive genetic effects and of unique environmental factors in liability to bulimia nervosa. The magnitude of the contribution of shared environment is less clear, but in the studies with the greatest statistical power, it appears to be less prominent than additive genetic factors.