The relation between risk factors for binge eating and bulimia nervosa: a population-based female twin study

Exploring the possibility of parents' broad internalizing phenotype acting through passive gene-environment correlations on daughters' disordered eating

Twin studies demonstrate significant environmental influences and a lack of genetic effects on disordered eating before puberty in girls. However, genetic factors could act indirectly through passive gene-environment correlations (rGE; correlations between parents' genes and an environment shaped by those genes) that inflate environmental (but not genetic) estimates. The only study to explore passive rGE did not find significant effects, but the full range of parental phenotypes (e.g., internalizing symptoms) that could impact daughters' disordered eating was not examined. We addressed this gap by exploring whether parents' internalizing symptoms (e.g., anxiety, depressive symptoms) contribute to daughters' eating pathology through passive rGE. Participants were female twin pairs (aged 8-14 years; M = 10.44) in pre-early puberty and their biological parents (n = 279 families) from the Michigan State University Twin Registry. Nuclear twin family models explored passive rGE for parents' internalizing traits/symptoms and twins' overall eating disorder symptoms. No evidence for passive rGE was found. Instead, environmental factors that create similarities between co-twins (but not with their parents) and unique environmental factors were important. In pre-early puberty, genetic factors do not influence daughters' disordered eating, even indirectly through passive rGE. Future research should explore sibling-specific and unique environmental factors during this critical developmental period.

Eating Disorders in the Adolescent Population:

Adolescents become vulnerable to developing eating disorders as they mature. Very little is known about the prevalence, etiology, assessment, treatment, and outcome of eating disorders among adolescents. In general, research on eating disorders continues to be plagued with design flaws. Future studies need to be prospective research based on larger, more diverse samples of adolescents that represent all developmental stages of adolescence. Consistent diagnostic criteria and definitions of treatment interventions and outcomes also need to be employed. In addition, research should address the identification of protective and risk factors that predict who will actually develop an eating disorder.

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.

Genome-wide association analysis of eating disorder-related symptoms, behaviors, and personality traits

Eating disorders (EDs) are common, complex psychiatric disorders thought to be caused by both genetic and environmental factors. They share many symptoms, behaviors, and personality traits, which may have overlapping heritability. The aim of the present study is to perform a genome-wide association scan (GWAS) of six ED phenotypes comprising three symptom traits from the Eating Disorders Inventory 2 [Drive for Thinness (DT), Body Dissatisfaction (BD), and Bulimia], Weight Fluctuation symptom, Breakfast Skipping behavior and Childhood Obsessive-Compulsive Personality Disorder trait (CHIRP). Investigated traits were derived from standardized self-report questionnaires completed by the TwinsUK population-based cohort. We tested 283,744 directly typed SNPs across six phenotypes of interest in the TwinsUK discovery dataset and followed-up signals from various strata using a two-stage replication strategy in two independent cohorts of European ancestry. We meta-analyzed a total of 2,698 individuals for DT, 2,680 for BD, 2,789 (821 cases/1,968 controls) for Bulimia, 1,360 (633 cases/727 controls) for Childhood Obsessive-Compulsive Personality Disorder trait, 2,773 (761 cases/2,012 controls) for Breakfast Skipping, and 2,967 (798 cases/2,169 controls) for Weight Fluctuation symptom. In this GWAS analysis of six ED-related phenotypes, we detected association of eight genetic variants with P < 10(-5) . Genetic variants that showed suggestive evidence of association were previously associated with several psychiatric disorders and ED-related phenotypes. Our study indicates that larger-scale collaborative studies will be needed to achieve the necessary power to detect loci underlying ED-related traits.

Differentiating purging and nonpurging bulimia nervosa and binge eating disorder

OBJECTIVE

To explore similarities and differences in clinical and personality variables across three groups: binge eating disorder (BED), bulimia nervosa-purging type (BN-P), and bulimia nervosa-non purging type (BN-NP).

METHOD

The participants were 102 female eating disorders patients (34 BED, 34 BN-P, and 34 BN-NP) consecutively admitted to the eating disorders unit, at the University Hospital of Bellvitge, and diagnosed according to DSM-IV criteria.

RESULTS

BED patients were older, and more likely to have personal and family history of obesity. A gradient in psychopathological scores emerged with BN-P patients having higher pathological scores on the SCL-90-R, followed by BN-NP and BED patients. No statistically significant differences were observed in personality traits.

DISCUSSION

Our data supported that eating disorders (namely BED, BN-NP, and BN-P) followed a linear trend in general psychopathology. Whereas personality may represent a shared vulnerability factor, differences in clinical severity suggest there to be a continuum with BN-P being the most severe and BED being the least severe.

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.

Interspecies genetics of eating disorder traits

Family and twin studies have indicated that genetic factors play a role in the development of eating disorders, such as anorexia and bulimia nervosa, but novel views and tools may enhance the identification of neurobiological mechanisms underlying these conditions. Here we propose an integrative genetic approach to reveal novel biological substrates of eating disorder traits analogous in mouse and human. For example, comparable to behavioral hyperactivity that is observed in 40-80% of anorexia nervosa patients, inbred strains of mice with different genetic backgrounds are differentially susceptible to develop behavioral hyperactivity when food restricted. In addition, a list of characteristics that are relevant to eating disorders and approaches to their measurement in humans together with potential analogous rodent models has been generated. Interspecies genetics of neurobehavioral characteristics of eating disorders has the potential to open new roads to identify and functionally test genetic pathways that influence neurocircuits relevant for these heterogeneous psychiatric disorders.

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

BACKGROUND

Objective binge eating (OBE) and self-induced vomiting (SIV) occur and co-occur across a range of eating disorders but the extent to which the risk factors for these two behaviours overlap is unclear. Examination of this overlap was the focus of the current report.

METHOD

A population of female Australian twins (n=1002), mean age 35 years (s.d.=2.11, range 28-40), participated in three waves of data collection and were assessed for lifetime disordered eating with a semi-structured interview at wave 3 and a self-report questionnaire at wave 1; risk factors were assessed via a self-report at waves 1 and 3.

RESULTS

Non-shared environmental influences were the largest contributor to the variance of both OBE and SIV, with a more modest contribution of genetic influences. Between 5% and 14% of the environmental risk factors for OBE and SIV were shared and 27-100% of genetic risk factors were shared. SIV initiation was predicted by higher neuroticism and novelty seeking and lower maternal and paternal care, whilst lower levels of perceived paternal care, higher lifetime BMI, and a wider BMI range predicted OBE initiation. Retrospective correlates associated with both SIV and OBE onset were parental comments about weight, whilst higher levels of parental conflict, expectations and criticism was associated with OBE onset only.

CONCLUSIONS

The substantial extent of non-overlap between risk factors for SIV and OBE suggests that each of these behavioural disturbances warrants future investigation in its own right, not only when they occur in conjunction with each other.

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.

Bulimia nervosa: an update and treatment recommendations

Bulimia nervosa is a common eating disorder in adolescent women. Biological, psychological, and social factors are implicated in onset and important in treatment. Diagnosis of the syndrome, but not its subtypes, can be made well using the DSM-IV system. Screening tools, laboratory findings, and physical findings can be helpful in making the diagnosis. Comorbid disorders include affective disorders, addictive disorders, anxiety disorders, personality disorders, and anorexia nervosa. The etiology of bulimia nervosa is complex, with biologic, psychological, social, and family factors, which likely differ somewhat from patient to patient. Treatment, accordingly, should be comprehensive, individualized, and multifaceted. Many patients respond well to the use of an antidepressant, and cognitive-behavioral therapy is a useful approach for many patients. Combining these two treatments seems to be a good strategy. Environmental and family issues also need to be addressed. Many patients are treated insufficiently. More research on bulimia nervosa specific to adolescence is needed.