Body dissatisfaction and drive for thinness in young adult twins

Associations between polygenic risk scores for cardiometabolic phenotypes and adolescent depression and body dissatisfaction

BACKGROUND

Adolescents with elevated body mass index (BMI) are at an increased risk for depression and body dissatisfaction. Type 2 diabetes (T2D) is an established risk factor for depression. However, shared genetic risk between cardiometabolic conditions and mental health outcomes remains understudied in youth.

METHODS

The current study examined associations between polygenic risk scores (PRS) for BMI and T2D, and symptoms of depression and body dissatisfaction, in a sample of 827 community adolescents (Mage = 13.63, SDage = 1.01; 76% girls). BMI, depressive symptoms, and body dissatisfaction were assessed using validated self-report questionnaires.

RESULTS

BMI-PRS was associated with phenotypic BMI (β = 0.24, p < 0.001) and body dissatisfaction (β = 0.17, p < 0.001), but not with depressive symptoms. The association between BMI-PRS and body dissatisfaction was significantly mediated by BMI (indirect effect = 0.10, CI [0.07-0.13]). T2D-PRS was not associated with depression or body dissatisfaction.

CONCLUSIONS

The results suggest phenotypic BMI may largely explain the association between genetic risk for elevated BMI and body dissatisfaction in adolescents. Further research on age-specific genetic effects is needed, as summary statistics from adult discovery samples may have limited utility in youth.

IMPACT

The association between genetic risk for elevated BMI and body dissatisfaction in adolescents may be largely explained by phenotypic BMI, indicating a potential pathway through which genetic predisposition influences body image perception. Furthermore, age-specific genetic research is needed to understand the unique influences on health outcomes during adolescence. By identifying BMI as a potential mediator in the association between genetic risk for elevated BMI and body dissatisfaction, the current findings offer insights that could inform interventions targeting body image concerns and mental health in this population.

Do risk factors differentiate DSM-5 and drive for thinness severity groups for anorexia nervosa?

BACKGROUND

The current study examined whether risk factors for anorexia nervosa (AN) were related to different levels of severity based on (a) the DSM-5/body mass index (BMI) and (b) drive for thinness (DT) severity ratings.

METHODS

The sample comprised 153 pairs of individuals with a lifetime diagnosis AN per DSM-IV criteria and their non-ED sisters (N = 306, mean age = 26.53; mean current BMI = 20.42 kg/m2). The Oxford risk factor interview was used to establish AN-related risk factors. Individuals were categorised into the DSM-5 severity groups based on their lowest BMI, while the DT subscale from the eating disorder inventory-2 was used to classify individuals with AN into low and high DT groups.

RESULTS

Multinominal regression models showed similar risk factors (e.g., perfectionism, having a history of being teased about weight and shape) contributed to the development of AN using the DSM-5 and DT severity ratings. Follow-up analyses across the severity groups for both indices revealed that only childhood perfectionism was found to be more common in the extreme severe DSM-5 BMI severity group compared to the severe DSM-5 group.

CONCLUSION

Overall, this study found little evidence for AN risk factors being related to the DSM-5 and DT severity ratings. However, given the novelty of this study, replication of the current results is warranted.

The ageing body: contributing attitudinal factors towards perceptual body size estimates in younger and middle-aged women

Over-estimation of body size, a core feature of eating disorders (EDs), has been well-documented both in young healthy and ED individuals. Yet, evidence that altered body perception might also affect older women is limited. Here, we examined whether attitudinal components of body image (i.e. the feelings an individual has about their body size and shape) might affect perceived actual and ideal body shape self-estimates in midlife, similarly to younger women. Thirty-two younger (mean age, 24.22 years) and 33 middle-aged (mean age, 53.79 years) women took part to a computerized body perception assessment of perceived, actual and ideal aspects of body image. Body mass index (BMI), societal and interpersonal aspects of appearance ideals, measured by means of Sociocultural Attitudes towards Appearance Questionnaire (SATAQ-4), and assessment of body uneasiness and concerns for specific body parts, measured by Body Uneasiness Test (BUT-A/B) scales, were also investigated. Younger and middle-aged women with larger BMI showed greater discrepancy in perceptual distortions from their perceived actual body size. However, middle-aged women with greater body part concerns overestimated their perceived body size, as opposed to younger women who were almost accurate. Unlike middle-aged women, younger women with higher body part concerns desired slimmer ideal body image than their perceived actual. Results suggest that distortions in the perceived actual and ideal body size self-estimates of younger and middle-aged women are best explained by a combination of BMI, body part concerns and the particular age group to which a participant belonged. In the future, a personalized approach for the assessment of women's perceptions and concerns of specific body areas during lifespan should be adopted.

A Narrative Review of Sex Differences in Eating Disorders: Is There a Biological Basis?

PURPOSE

Eating disorders and their core symptoms (eg, binge eating, body weight/shape concerns) disproportionately affect females, and these sex-differentiated effects become prominent during and after puberty. Although psychosocial influences such as heightened sociocultural pressures for thinness in girls and women contribute to this sex imbalance, biological factors could also play an important role.

METHODS

This narrative review summarizes evidence of biological factors underlying the sex-differentiated prevalence of eating pathology as well as within-sex variability in risk.

FINDINGS

There are sex differences in the pubertal emergence of genetic effects on eating pathology (adrenarche in males; gonadarche in females), and at least some genetic contributions to eating pathology seem to vary between the sexes. Furthermore, sex steroid hormones (eg, testosterone, estradiol, progesterone) are leading contributors to differential risk for eating pathology in males and females across the life span. Emerging data suggest that between-sex and within-sex variability in risk might occur via hormone-driven modulation (activation/deactivation) of genetic influences and neural responsiveness to food-related cues.

IMPLICATIONS

There is a biological basis to heightened risk for eating pathology in females, relative to males, as well as unique biological influences within each sex. Findings from this review highlight the importance of studying both sexes and considering sex-specific biological mechanisms that may underlie differential risk for eating pathology.

Rank-Order of Body Shapes Reveals Internal Hierarchy of Body Image

How do individuals rank body shapes? Does this relate to the body part one is most dissatisfied with? Our study investigates whether one can generalize regarding how women represent the body. Three BMI-calibrated images from the Photographic Figure Rating Scale, representative of thin (BMI = 14.72), medium (BMI = 20.33), and large (BMI = 29.26) shapes, were divided into torso, legs and arms, and saved as individual images on a black background. Of 27 possible composite images, 8 were chosen based on a Torso (thin vs. large) × Leg (thin/large vs. medium) × Arm (thin vs. large) design. Our 44 female participants ordered these from thinnest to largest. This was first according to torso, then leg, and finally arm: 41 individuals agreed on the thinnest image (thin torso, thin legs, thin arms), followed by a second image (thin torso, thin legs, large arms, n = 26; or thin torso, medium legs, thin arms, n = 10). One participant differed markedly in her choice of the first image (large torso, medium legs, thin arms). Interestingly, she scored 10 on the EDI-2 scale of Bulimic Tendencies, revealing high risk for bulimia, suggesting that our task might be useful for studying eating disorders. Our juxtaposition of two analytic procedures-partial order scalogram analysis (POSAC) and cluster analysis-enables one to uncover such outliers in a data set. Importantly, the 2D POSAC space clearly reveals the hierarchical structure of the body image.

The Direct and Indirect Effects of Online Social Support, Neuroticism, and Web Content Internalization on the Drive for Thinness among Women Visiting Health-Oriented Websites

One of the debates about media usage is the potential harmful effect that it has on body image and related eating disturbances because of its representations of the “ideal body”. This study focuses on the drive for thinness among the visitors of various health-oriented websites and online platforms because neither has yet been sufficiently studied in this context. Specifically, this study aims to bring more insight to the risk factors which can increase the drive for thinness in the users of these websites. We tested the presumption that web content internalization is a key factor in this process, and we considered the effects of selected individual factors, specifically the perceived online social support and neuroticism. We utilized survey data from 445 Czech women (aged 18–29, M = 23.5, SD = 3.1) who visited nutrition, weight loss, and exercise websites. The results showed a positive indirect link between both perceived online social support and neuroticism to the drive for thinness via web content internalization. The results are discussed with regard to the dual role of online support as both risk and protective factor. Moreover, we consider the practical implications for eating behavior and weight-related problems with regard to prevention and intervention.

Eating Behaviors in Healthy Young Adult Twin Pairs Discordant for Body Mass Index

We aimed to study the eating behavioral traits that associate with body mass index (BMI) among BMI-discordant twin pairs. This cross-sectional study examined self-reported eating behaviors in 134 healthy young adult twin pairs (57 monozygotic [MZ] and 77 same-sex dizygotic [DZ]), of whom 29 MZ and 46 DZ pairs were BMI discordant (BMI difference ≥ 3 kg/m2). In both MZ and DZ BMI-discordant pairs, the heavier co-twins reported being less capable of regulating their food intake optimally than their leaner co-twins, mainly due to ‘frequent overeating’. Furthermore, the heavier co-twins reported augmented ‘disinhibited eating’, ‘binge-eating scores’ and ‘body dissatisfaction’. The twins agreed more frequently that the heavier co-twins (rather than the leaner co-twins) ate more food in general, and more fatty food, in particular. No significant behavioral differences emerged in BMI-concordant twin pairs. Overeating — measured by ‘frequent overeating’, ‘disinhibited eating’ and ‘binge-eating score’ — was the main behavioral trait associated with higher BMI, independent of genotype and shared environment.

Leading by example: Development of a maternal modelling of positive body image scale and relationships to body image attitudes

The aims of this study were to develop a measure, the Role Modelling of Body Image (Attitudes and Behaviors) Questionnaire (RMBI-Q), to determine maternal perceptions of their body image role modelling in front of their children, and to evaluate how role modelling differs with demographic characteristics to identify characteristics of mothers who may require assistance in being a positive role model. Participants were a community-based sample of 887 mothers who provided demographic information and completed the RMBI-Q, Body Appreciation Scale (BAS-2), and a measure of dietary restraint (DEBQ) in an online questionnaire. Exploratory factor analysis revealed one 7-item factor for the RMBI-Q. Confirmatory factor analysis revealed that removal of an item was necessary for model fit, and thus, a 6-item version of the RMBI-Q was evaluated. Good internal consistency, test-retest reliability, content validity, and convergent validity were found. Higher scores on the RMBI-Q correlated with greater maternal body appreciation and lower dietary restraint. More positive role modelling was reported by mothers with lower body mass index and younger children. The RMBI-Q is useful for assessing maternal modelling of positive behaviors that may improve children's body image. Findings highlight avenues for body image interventions for mothers.

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.

Associations Between Alcohol Involvement and Drive for Thinness and Body Dissatisfaction in Adolescent Twins: A Bivariate Twin Study

BACKGROUND

Alcohol involvement has familial associations with bulimic symptoms (i.e., binge eating, inappropriate compensatory behaviors), with several studies indicating a genetic overlap between the two. It is unclear whether overlapping familial risk with alcohol involvement extends to other eating disorder symptoms. Understanding the genetic overlap between alcohol involvement and other eating disorder symptoms may aid in more targeted interventions for comorbid alcohol use-eating disorder symptoms. Thus, we investigated associations between alcohol involvement and 2 core eating disorder symptoms: drive for thinness and body dissatisfaction in adolescent female and male twins.

METHODS

We assessed 3 levels of alcohol involvement: alcohol use in the last month, having ever been intoxicated, and alcohol intoxication frequency via self-report. The Eating Disorder Inventory-II assessed drive for thinness and body dissatisfaction. Sex-specific biometrical twin modeling examined the genetic overlap between alcohol involvement and eating disorder symptoms.

RESULTS

Phenotypic associations between alcohol involvement, drive for thinness, and body dissatisfaction were significantly greater in girls compared with boys. A majority of the associations between alcohol involvement, drive for thinness, and body dissatisfaction in girls, but not boys, met our threshold for twin modeling (phenotypic r > 0.20). Moderate genetic correlations were observed between the 3 aspects of alcohol involvement and drive for thinness. Moderate genetic correlations were observed between alcohol use and intoxication frequency and body dissatisfaction.

CONCLUSIONS

Together with the literature on alcohol involvement and bulimic symptoms, these findings suggest a generalized association between alcohol involvement and eating disorder symptoms in girls, whereas this association may be symptom specific in boys. Genetic correlations indicate that the amount and direction of this genetic overlap differs across specific symptoms. When intervening on comorbid alcohol involvement and eating disorder symptoms, it may be important to target-specific eating disorder symptoms.

Childhood body mass index and development of eating disorder traits across adolescence

OBJECTIVE

Understanding the role of premorbid body mass index (BMI) in the emergence of eating disorders may be key to identifying effective prevention strategies. We explore relations between BMI and eating disorders traits in young twins.

METHOD

The effect of BMI at age 9/12 and 15 on eating disorder traits measured using the Eating Disorders Inventory-2 (EDI) at ages 15 and 18 was examined using bivariate modelling in a longitudinal population sample of Swedish twins.

RESULTS

The correlation between BMI and EDI within individuals was stable across all ages and remained significant after adjusting for later BMI. Bivariate analysis indicated significant positive genetic correlations between BMI ages 9/12 and 15 and subsequent EDI scores. The relationship remained significant for BMI age 9/12 and EDI age 15 in the adjusted model, indicating a longitudinal association.

CONCLUSION

Our results have implications for conceptualizing the interrelation of BMI and eating disorders across childhood and adolescence.

Conceptualizing body dissatisfaction in eating disorders within a self-discrepancy framework: a review of evidence

Body dissatisfaction, the negative subjective evaluation of one's body, is associated with many negative psychological and physical health consequences. One conceptualization of body dissatisfaction includes an experience of discrepancy between perceived actual and ideal body shapes. This paper reviews the literature on three facets of body dissatisfaction from the framework of self-discrepancy theory: perceptions of current weight, ideal body weight, and the relative importance of conforming to ideals. We review components of body dissatisfaction among healthy individuals and eating-disordered individuals. We also address the conceptualization's relationship among body dissatisfaction, weight history, and dieting to expand the impact of body dissatisfaction research and to provide more information on the nature and treatment of eating disorders.

Successful weight maintainers among young adults-A ten-year prospective population study

OBJECTIVES

To assess factors associated with successful weight maintenance over ten years in a prospective general population sample of young adults.

MATERIAL AND METHODS

Our study comprised 2452 women and 2227 men born in 1975-1979 (mean age at baseline 24 years, attrition 27.1%). Weight maintenance was defined as weight maintained within ±5% of baseline body mass index (BMI). We examined the role of various sociodemographic and lifestyle factors in successful weight maintenance.

RESULTS

Relatively few young adults were able to maintain their weight over ten years (28.6% of women vs. 23.0% of men); net weight loss was uncommon (7.5% and 3.8%). Most participants gained weight (mean annual weight gain was 0.9 kg in women and 1.0 kg in men). Among women, exercise was associated with successful weight maintenance, but having two or more children, frequent use of sweet drinks, irregular eating, history of dieting (intentional weight loss) and low life satisfaction were associated with weight gain. Among men, higher baseline BMI and higher education were associated with successful weight maintenance, whereas irregular eating, history of dieting and smoking were associated with weight gain.

CONCLUSIONS

Only about a quarter of young adults were able to resist weight gain. Regular eating and having no history of dieting were associated with successful weight maintenance in young women and men.

Fear of food prospectively predicts drive for thinness in an eating disorder sample recently discharged from intensive treatment

Fears of food are common in individuals with eating disorders and contribute to the high relapse rates. However, it is unknown how fears of food contribute to eating disorder symptoms across time, potentially contributing to an increased likelihood of relapse. Participants diagnosed with an eating disorder (N=168) who had recently completed intensive treatment were assessed after discharge and one month later regarding fear of food, eating disorder symptoms, anxiety sensitivity, and negative affect. Cross lagged path analysis was utilized to determine if fear of food predicted subsequent eating disorder symptoms one month later. Fear of food-specifically, anxiety about eating and feared concerns about eating-predicted drive for thinness, a core symptom domain of eating disorders. These relationships held while accounting for anxiety sensitivity and negative affect. There is a specific, direct relationship between anxiety about eating and feared concerns about eating and drive for thinness. Future research should test if interventions designed to target fear of food can decrease drive for thinness and thereby prevent relapse.

Family Relations and Psychopathology: Examining Depressive and Bulimic Symptomatology

Despite early theories suggesting that family dysfunction (FD) may cause disordered eating, FD has been linked with other disorders and is a non-specific risk factor for disordered eating. We examined one potential model of the way FD relates to disordered eating, drawing on research that identified depression as a risk factor for bulimia. We examined whether depression symptoms (DEPs) partially mediated the relationship between family cohesion (as a measure of FD) and bulimic symptoms (BNs) using a sample of 215 never-married college women under age 20. Perceptions that one's family was less cohesive (or more disengaged) was associated with increased DEPs and BNs. Moreover, DEPs partially mediated the influence of cohesion on BNs through a significant indirect effect. Both family systems in general and treatment of mood difficulties may be important considerations in the prevention of disordered eating, and prevention efforts that include family relationships should be experimentally explored.

The longitudinal relationship between worry and disordered eating: Is worry a precursor or consequence of disordered eating?

Worry, the core component of generalized anxiety disorder, is associated with disordered eating. However, it is unclear whether worry is a precursor to disordered eating or whether worry is a consequence of disordered eating (or both). The current study tested if worry prospectively predicted disordered eating symptoms and vice-versa across six months. Young adult women (n=300) completed a measure of worry and disordered eating at Time 1, and two months and six months later. A prospective path model utilizing structural equation modeling investigated if worry predicted disordered eating (and vice-versa). Worry prospectively predicted drive for thinness across both two and six months while controlling for previous levels of worry. In the opposite direction, drive for thinness did not predict worry over time. There were no prospective relationships between worry and bulimia or body dissatisfaction. Therefore, interventions focusing on decreasing worry could be effective in preventing and treating excessive concerns about thinness and their associated impairment.

Psychosocial Determinants of Weight Loss Among Young Adults With Overweight and Obesity: HOW DOES DRIVE FOR THINNESS AFFECT WEIGHT LOSS?

PURPOSE

The ardent wish to lose weight, drive for thinness (DT), might be 1 psychosocial contributor to weight loss (WL) in adults with overweight and obesity. In examining DT as a predictor of WL, it is important to determine whether its predictive value is equal in males and females and whether it exerts its effects primarily through changes in diet or physical activity (PA).

METHODS

Two-hundred three men and women with overweight and obesity (body mass index >25 kg/m; aged 21-35 years; 47% female) participated in this 12-month observational study. DT score and demographic information were collected at baseline. Participants were measured at quarterly intervals for objectively measured PA, energy intake, and anthropometrics. Linear mixed regression analyses determined whether DT predicted WL over time and whether these effects were moderated by sex. Followup mediation analyses determined whether the effects of DT on WL could be explained by either changes in diet or PA.

RESULTS

Females reported higher DT as compared with males at baseline (P < .001). We observed a significant sex × time × DT interaction on WL (P < .04), such that higher DT predicted WL in males (P < .04), but not in females (P = .54). This effect of DT on WL in overweight and obese males was mediated by changes in PA (indirect effect, -0.43; 95% CI, -1.52 to -0.05), but not changes in energy intake.

CONCLUSIONS

Among young adults with overweight and obesity who have higher DT, PA appears to be more important to WL than caloric restriction, particularly in males.

Physical and social factors associated with early adolescent headache and stomachache pain

PURPOSE

Approximately one third of adolescents in the United States report experiencing frequent headaches and stomachaches. We examined the association of psychosocial and physical factors with the report of weekly headaches or stomachaches using a representative sample of US teens.

METHODS

Data for this project are from the survey of Health Behavior in School-Aged Children (HBSC), 2005-2006, a nationally representative sample of students in grades 6-10 in the United States. The total sample includes 12,070 students aged 11-17. Using logistic regression we modeled chronic headache and stomachache separately with the same set of physical predictors (dieting and substance use habits) and psychosocial predictors (attitudes towards self-image, peers, and family) along with demographic controls.

RESULTS

Almost 20% of respondents experienced headaches weekly, and 12% experienced abdominal pain. Both physical and psychosocial factors were predictive of chronic symptoms. Increased substance usage and unhealthy eating practices were associated with the likelihood of experiencing both headaches and stomachaches. Negative self-image, family relationships, and school life were also predictive of symptom frequency.

CONCLUSION

Headaches and stomachaches are associated with poor eating and substance use habits, as well as problems with self-image or social relationships among adolescents. For health care professionals, a holistic approach is needed to effectively address symptoms and prevent long-term health problems.

Disordered eating behavior, health and motives to exercise in young men: cross-sectional population-based MOPO study

BACKGROUND

Being overweight is an increasing problem among young people, among whom disordered eating behavior is linked with weight problems as well as unhealthy weight control. The aim of the present study was to investigate whether health factors and motives to exercise differ in young men by the type of disordered eating behavior.

METHODS

The population-based, cross-sectional MOPO study consisted of 2,096 young Finnish men (mean age 17.9, SD 0.7) attending compulsory call-ups for military service in the Oulu area in 2010, 2011, and 2013. They responded to a questionnaire that included two subscales of the Eating Disorder Inventory-3 indicating drive for thinness and bulimic behavior and questions on health, physical activity, and motives to exercise. The association between disordered eating behavior and related factors was analyzed by binary logistic regression.

RESULTS

Altogether, 6.9 % (n = 145) of the men had symptoms of disordered eating, i.e., 5.4 % had a drive for thinness (n = 114) and 3.7 % had bulimic behavior (n = 77). Drive for thinness was associated with a perception of being overweight (OR 3.7; 95 % CI 2.2-6.1), poor self-rated health (2.3; 1.2-4.4), more leisure sitting time (1.1; 1.0-1.2), and body-related exercise motives (body acceptance: 3.0; 1.7-5.2; weight loss: 2.5; 1.4-4.4). Bulimic behavior was positively associated with poor self-rated health (2.6; 1.1-5.8) and several motives to exercise, i.e., due to another person's suggestion (2.8; 1.6-4.8), competitive sports (2.1; 1.2-3.7), body acceptance (2.1; 1.1-3.9), and weight loss (1.9; 1.1-3.3), but inversely associated with health/fitness-related exercise motives (health promotion: 0.3; 0.1-0.5; muscular strength or physical performance: 0.5; 0.2-0.9).

CONCLUSIONS

In young men, disordered eating behavior was associated with being overweight, having poor self-rated health, and having a greater amount of leisure sitting time as well as non-health-related motives to exercise. In order to recognize those at risk for disordered eating behavior, evaluating these factors could be beneficial.

Scrutinizing Immutability: Research on Sexual Orientation and U.S. Legal Advocacy for Sexual Minorities

We review scientific research and legal authorities to argue that the immutability of sexual orientation should no longer be invoked as a foundation for the rights of individuals with same-sex attractions and relationships (i.e., sexual minorities). On the basis of scientific research as well as U.S. legal rulings regarding lesbian, gay, and bisexual (LGB) rights, we make three claims: First, arguments based on the immutability of sexual orientation are unscientific, given what we now know from longitudinal, population-based studies of naturally occurring changes in the same-sex attractions of some individuals over time. Second, arguments based on the immutability of sexual orientation are unnecessary, in light of U.S. legal decisions in which courts have used grounds other than immutability to protect the rights of sexual minorities. Third, arguments about the immutability of sexual orientation are unjust, because they imply that same-sex attractions are inferior to other-sex attractions, and because they privilege sexual minorities who experience their sexuality as fixed over those who experience their sexuality as fluid. We conclude that the legal rights of individuals with same-sex attractions and relationships should not be framed as if they depend on a certain pattern of scientific findings regarding sexual orientation.

Genetic and environmental influences on psychological traits and eating attitudes in a sample of Spanish schoolchildren

INTRODUCTION

The heritability of eating disorders has been estimated to range from 22% to over 62%.The aim of this study is to determine the relative influence of genetics and environment that contribute to the drive for thinness, body dissatisfaction, perfectionism, and ineffectiveness, by evaluating sex differences in a sample of adolescent twins from Valencia, Spain.

MATERIAL AND METHODS

Five hundred eighty-four pairs of adolescent twins between 13 and 18 years of age completed the study. To determine zygosity, teachers responded to a questionnaire on physical similarity. Psychological traits of eating disorders were assessed with four sub-scales of the Eating Disorder Inventory (EDI); drive for thinness, body dissatisfaction, perfectionism, and ineffectiveness. Twin models were used to assess genetic and environmental (common and unique) factors affecting these four psychological traits.

RESULTS

All four traits showed significant genetic contributions among girls, with heritability estimates of 37.7% for ineffectiveness, 42.8% for perfectionism, 56.9% for drive for thinness, and 65.5% for body dissatisfaction. Among boys, body dissatisfaction showed no additive genetic contributions, indicating significant shared and individual specific environment effects. The three other traits in boys showed significant additive genetic contributions, but were lower than in girls.

CONCLUSIONS

With the exception of body dissatisfaction in boys, psychological traits of eating disorders show heritability patterns that differ according to sex.

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.

Psychological well-being in adolescents with excess weight

BACKGROUND

Self-esteem, perceived health, weight satisfaction, eating habits, physical activity, friendships, intimate relationships, smoking and substance use habits can be regarded as important correlates of psychological well-being in adolescence.

AIM

The present study aimed to determine whether problems in the above-mentioned elements of psychological well-being were more prevalent among mid-adolescent pupils with excess weight than among their healthy-weight peers.

METHODS

The study participants comprised 178 adolescents with excess weight and 1087 healthy-weight peers with a mean age of 14.7 years attending the 8th grade at secondary school. The Rosenberg Self-Esteem Scale, the Eating Disorder Inventory and a questionnaire assessing health- and food-related attitudes and habits were used.

RESULTS

The adolescents with excess weight more often reported weight dissatisfaction, abnormal eating habits and signs of eating disorder pathology than those with healthy weight. No significant difference in self-esteem was observed between weight groups. The proportion of adolescents who were non-smokers, did not use alcohol and had one or more close friends did not differ between those with excess and healthy weight. However, a lower proportion of excess-weight adolescents had dating experience. Inadequate physical activity was highly prevalent among adolescents in both weight groups.

CONCLUSIONS

Despite the high prevalence of eating pathology and weight dissatisfaction, most mid-adolescent pupils with excess weight expressed good psychological health. Targeted psychological interventions should be offered to some adolescents with overweight problems.

Self-harm history predicts resistance to inpatient treatment of body shape aversion in women with eating disorders: The role of negative affect

Although self-harm has been observed among patients with eating disorders, the effects of such tendencies on treatment outcomes are unclear. The current study employed structural equation modeling to (a) evaluate the relationship between self-harm and changes in body dissatisfaction and drive for thinness in a large sample of patients (n = 2061) who underwent inpatient treatment, and (b) to examine whether the relationship between self-harm and changes in body dissatisfaction and drive for thinness during inpatient treatment remains significant when controlling for change in negative affect during treatment. Results revealed that patients with a history of self-harm reported significantly less reduction in body dissatisfaction and drive for thinness following treatment. Patients experiencing less change in negative affect also reported significantly less reduction in body dissatisfaction and drive for thinness after discharge from treatment. However, the association between history of self-harm and reduction in body dissatisfaction and drive for thinness after treatment became non-significant when controlling for change in negative affect. This pattern of findings was also replicated among patients with a primary diagnosis of anorexia nervosa (n = 845), bulimia nervosa (n = 565), and eating disorder not otherwise specified (n = 651). The implications of these findings for delineating the specific role of self-harm in the nature and treatment of eating disorders are discussed.

Body size dissatisfaction among young adults from the 1982 Pelotas birth cohort

BACKGROUND/OBJECTIVES

To identify the prevalence and factors associated with body dissatisfaction.

SUBJECTS/METHODS

Birth cohort study investigating 4100 subjects (2187 men and 1913 women) aged between 22 and 23 years who answered questionnaires, including the body satisfaction Stunkard Scale were included in the study; they were weighed and measured. Multinomial logistic regression was used in the crude and adjusted analyses.

RESULTS

The prevalence of body dissatisfaction was 64% (95% CI, 62.7-65.6); 42% (95% CI, 40.6-43.6) of the subjects reported feeling larger than the desired body size, and 22% (95% CI, 20.7-23.3) reported feeling smaller than desired. Underweight subjects, subjects with less schooling, poor and sedentary male subjects with low psychological well-being and female subjects who were already mothers were more likely to express body dissatisfaction, perceiving their body as smaller than the desirable body size. The prevalence of body dissatisfaction was also high among overweight subjects, subjects with a high socioeconomic status and married female subjects, who perceived their body size as too large. Minor psychiatric disorders were associated with body dissatisfaction in all subjects, regardless of perceiving themselves as larger or smaller than the desired body size. Most women perceived themselves as larger, but similar proportions of men perceived themselves as too small or too large.

CONCLUSIONS

Body dissatisfaction was observed among men and women with normal weight, but it was more evident in the obese individuals. Regardless of the nutritional status, both men and women should be appropriately counseled because body size perception can lead to unhealthy behaviors in relation to diet and physical activity.

The role of reproductive hormones in the development and maintenance of eating disorders

Much remains to be understood about the etiology of eating disorders. There is substantial evidence that reproductive hormones, specifically estrogens, play a direct role in normal food intake. Evidence is increasing that the reproductive hormones play a role in the abnormal food intake associated with eating disorders. For example, there is an inverse association between estradiol and eating disorder symptoms. Preliminary studies also suggest that hormone augmentation may be a beneficial adjunct to the standard treatment of choice for eating disorders. However, research is limited, so definitive conclusions about the benefit of hormone augmentation in treatment cannot be drawn. Future research, with a focus on translational studies, should continue to explore the role of reproductive hormones in the vulnerability to and maintenance of eating disorders.

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.

Puberty as a critical risk period for eating disorders: a review of human and animal studies

This article is part of a Special Issue "Puberty and Adolescence". Puberty is one of the most frequently discussed risk periods for the development of eating disorders. Prevailing theories propose environmentally mediated sources of risk arising from the psychosocial effects (e.g., increased body dissatisfaction, decreased self-esteem) of pubertal development in girls. However, recent research highlights the potential role of ovarian hormones in phenotypic and genetic risk for eating disorders during puberty. The goal of this paper is to review data from human and animal studies in support of puberty as a critical risk period for eating disorders and evaluate the evidence for hormonal contributions. Data are consistent in suggesting that both pubertal status and pubertal timing significantly impact risk for most eating disorders in girls, such that advanced pubertal development and early pubertal timing are associated with increased rates of eating disorders and their symptoms in both cross-sectional and longitudinal research. Findings in boys have been much less consistent and suggest a smaller role for puberty in risk for eating disorders in boys. Twin and animal studies indicate that at least part of the female-specific risk is due to genetic factors associated with estrogen activation at puberty. In conclusion, data thus far support a role for puberty in risk for eating disorders and highlight the need for additional human and animal studies of hormonal and genetic risk for eating disorders during puberty.

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.

Influence of college peers on disordered eating in women and men at 10-year follow-up

Research supports both concurrent and prospective associations between peer behaviors and disordered eating levels in late adolescent and young adult men and women. However, no study has examined peer influence after a follow-up duration over which peer groups change dramatically. This study examined how college roommates' dieting predicted disordered eating levels in women (n = 566) and men (n = 233) at 10-year follow-up. For women, college roommates' dieting significantly predicted Eating Disorder Inventory Drive for Thinness and Bulimia scores and purging at 10-year follow-up. Findings highlight the potential for school-based, peer-led interventions to have long-term benefits in women.

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.

Body dissatisfaction and body mass in girls and boys transitioning from early to mid-adolescence: additional role of self-esteem and eating habits

BACKGROUND

In the transition from early to mid-adolescence, gender differences in pubertal development become significant. Body dissatisfaction is often associated with body mass, low self-esteem and abnormal eating habits. The majority of studies investigating body dissatisfaction and its associations have been conducted on female populations. However, some evidence suggests that males also suffer from these problems and that gender differences might already be observed in adolescence.

AIMS

To examine body dissatisfaction and its relationship with body mass, as well as self-esteem and eating habits, in girls and boys in transition from early to mid-adolescence.

METHODS

School nurses recorded the heights and weights of 659 girls and 711 boys with a mean age of 14.5 years. The Rosenberg Self-Esteem Scale and the Body Dissatisfaction subscale of the Eating Disorder Inventory were used as self-appraisal scales. Eating data were self-reported.

RESULTS

The girls were less satisfied with their bodies than boys were with theirs (mean score (SD): 30.6 (SD 12.2) vs. 18.9 (SD 9.5); p < 0.001). The girls expressed most satisfaction with their bodies when they were underweight, more dissatisfaction when they were of normal weight and most dissatisfaction when they had excess body weight. The boys also expressed most satisfaction when they were underweight and most dissatisfaction when they had excess body weight. The boys reported higher levels of self-esteem than did the girls (mean (SD): 31.3 (4.8) vs. 28.0 (5.9); p < 0.001). The adolescents self-reporting abnormal eating habits were less satisfied with their bodies than those describing normal eating habits (mean (SD): 33.0 (12.9) vs. 21.2 (10.2); p < 0.001).

CONCLUSIONS

Body mass, self-esteem and eating habits revealed a significant relationship with body dissatisfaction in the transitional phase from early to mid-adolescence in girls and boys, but significant gender differences were also found.

The effects of puberty on genetic risk for disordered eating: evidence for a sex difference

BACKGROUND

Differences in genetic influences on disordered eating are present across puberty in girls. Heritability is 0% before puberty, but over 50% during and after puberty. Emerging data suggest that these developmental differences may be due to pubertal increases in ovarian hormones. However, a critical piece of evidence is lacking, namely, knowledge of genetic influences on disordered eating across puberty in boys. Boys do not experience increases in ovarian hormones during puberty. Thus, if pubertal increases in genetic effects are present in boys, then factors in addition to ovarian hormones may drive increases in heritability in girls. The current study was the first to examine this possibility in a sample of 1006 male and female twins from the Michigan State University Twin Registry.

METHOD

Disordered eating was assessed with the Minnesota Eating Behavior Survey. Pubertal development was assessed with the Pubertal Development Scale.

RESULTS

No significant differences in genetic influences on disordered eating were observed in males across any developmental stage. Heritability was 51% in boys during pre-puberty, puberty and young adulthood. By contrast, in girls, genetic factors accounted for 0% of the variance in pre-puberty, but 51% of the variance during puberty and beyond. Sex differences in genetic effects were only significant during pre-puberty, as the best-fitting models constrained heritability to be equal across all males, pubertal females and young adult females.

CONCLUSIONS

The results highlight sex-specific effects of puberty on genetic risk for disordered eating and provide indirect evidence of a role for ovarian hormones and/or other female-specific factors.

Muscle Dissatisfaction and Muscle-Enhancing Substance Use: A Population-Based Twin Study in Young Adult Men

In the population-based FinnTwin16 study, proportions of genetic and environmental factors contributing to muscle dissatisfaction and muscle-enhancing substance use were assessed in 319 pairs of twin brothers: 141 monozygotic (MZ) and 178 dizygotic (DZ) pairs. In addition there were 86 twin individuals from pairs in which only one co-twin responded. Of all respondents, 30% experienced high muscle dissatisfaction. The corresponding proportion of muscle-enhancing substance use was 10%. The subjects were similar in age (23.8 years, 95% confidence interval [CI] 23.76–23.84), body mass index (23.7, 95% CI 23.5–23.9), and waist circumference (84.5 cm, 95% CI 83.7–85.2), independent of their muscle dissatisfaction or muscle-enhancing substance use status and independent of their zygosity. The MZ polychoric correlation for muscle dissatisfaction was .39 (95% CI .17–.58) and .27 for DZ pairs (95% CI .07–.46). The MZ tetrachoric correlation for muscle-enhancing substance use was .65 (95% CI .28–.87) and .56 for DZ pairs (95% CI .26–.78). The AE model, where additive genetic factors (A) accounted for 42% (95% CI .23–.59) and unique environmental factors (E) 58% (95% CI .41–.77) of the liability, provided the best fit for muscle dissatisfaction. The CE model, where common environmental factors (C) accounted for 60% (95% CI .37–.77) and unique environmental factors (E) 40% (95% CI .23–.63) of the liability, provided the best fit for muscle-enhancing substance use. Both genetic and unique (nonfamilial) environmental factors are involved in muscle dissatisfaction in the population. Nongenetic factors (both familial and non-familial) appear to best explain the use of muscle-enhancing substances.

Absence of association between specific common variants of the obesity-related FTO gene and psychological and behavioral eating disorder phenotypes

Extensive population-based genome-wide association studies have identified an association between the FTO gene and BMI; however, the mechanism of action is still unknown. To determine whether FTO may influence weight regulation through psychological and behavioral factors, seven single-nucleotide polymorphisms (SNPs) of the FTO gene were genotyped in 1,085 individuals with anorexia nervosa (AN) and 677 healthy weight controls from the international Price Foundation Genetic Studies of Eating Disorders. Each SNP was tested in association with eating disorder phenotypes and measures that have previously been associated with eating behavior pathology: trait anxiety, harm-avoidance, novelty seeking, impulsivity, obsessionality, compulsivity, and concern over mistakes. After appropriate correction for multiple comparisons, no significant associations between individual FTO gene SNPs and eating disorder phenotypes or related eating behavior pathology were identified in cases or controls. Thus, this study found no evidence that FTO gene variants associated with weight regulation in the general population are associated with eating disorder phenotypes in AN participants or matched controls.

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.

Who is The Fairest One of All? How Evolution Guides Peer and Media Influences on Female Body Dissatisfaction

Much attention has focused on the influence of media images of thin women on body dissatisfaction among female viewers. Disagreement exists regarding the nature of media influences, with meta-analytic results suggesting only small effect sizes. Fewer researchers have focused on the role of peer influences and peer competition on female body dissatisfaction. Furthermore, the relation between body dissatisfaction and eating disorders may be more complex than is often implied in the media effects literature. Links between body dissatisfaction and eating disorders may be overstated, and some eating disorders, primarily anorexia nervosa, may not always be motivated primarily by body dissatisfaction. The current paper discusses these issues from an evolutionary perspective, examining how sociocultural forces influence the intensity of female competition and how such competition effects body dissatisfaction.

Body evaluation and coital onset: a population-based longitudinal study

This study examined the temporal relationship between body evaluation and coital onset. In a population-based longitudinal study, 1449 Norwegian girls and boys between 12 and 15 years of age were followed at 4 waves over a span of 13 years. Body evaluation was used in order to predict coital onset besides romantic appeal and psychological problems. For girls early in adolescence, body evaluation did not influence the probability of coital onset during the first 2-year period. In the subsequent 5-year period, body dissatisfaction increased the probability for coital onset when romantic appeal was held constant. Body evaluation did not influence the odds of coital onset among boys. The findings imply that the pattern of association between body evaluation and coital onset differs according to the timing of coital onset for girls. Future research needs to distinguish body image from romantic appeal in relation to first time sexual experiences.

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.

Unhealthy weight control behaviours in adolescent girls: a process model based on self-determination theory

This study used self-determination theory (Deci, E.L., & Ryan, R.M. (2000). The 'what' and 'why' of goal pursuits: Human needs and the self-determination of behavior. Psychological Inquiry, 11, 227-268.) to examine predictors of body image concerns and unhealthy weight control behaviours in a sample of 350 Greek adolescent girls. A process model was tested which proposed that perceptions of parental autonomy support and two life goals (health and image) would predict adolescents' degree of satisfaction of their basic psychological needs. In turn, psychological need satisfaction was hypothesised to negatively predict body image concerns (i.e. drive for thinness and body dissatisfaction) and, indirectly, unhealthy weight control behaviours. The predictions of the model were largely supported indicating that parental autonomy support and adaptive life goals can indirectly impact upon the extent to which female adolescents engage in unhealthy weight control behaviours via facilitating the latter's psychological need satisfaction.

Reduced body size and shape-related symptoms in young adults born preterm with very low birth weight: Helsinki study of very low birth weight adults

OBJECTIVE

To test the hypothesis that being born prematurely with very low birth weight (VLBW) (birth weight<or=1500 g) is associated with subphenotypes of eating disorders (dissatisfaction with body shape and pursuit of thinness) in young adulthood.

STUDY DESIGN

Preterm-born VLBW subjects (n=163) and controls (n=189) born at term completed 3 subscales of Eating Disorder Inventory-2 questionnaire (EDI): Drive for Thinness, Body Dissatisfaction, and Bulimia. Data were analyzed with multiple linear regression adjusted for confounders.

RESULTS

Among both sexes, EDI total scores were lower in VLBW subjects than in controls. The fully adjusted difference was -11.0% (95% CI, -18.4%, -2.2%) for women and -11.2% (95% CI, -20.2%, -1.3%) for men. Among women the lower scores in VLBW adults were observed in each EDI subscale. Results were similar when adjusted also for fat percentage, measured by dual-energy x-ray absorptiometry. Of the covariates, higher body mass index and higher score in Beck Depression Inventory contributed significantly to a higher EDI total score.

CONCLUSIONS

Young adults, particularly women, born prematurely with VLBW have fewer body size and shape-related symptoms and possibly lower risk for eating disorders than their term-born peers.

A longitudinal investigation of the relationship between disordered eating attitudes and behaviors and parent-child conflict: a monozygotic twin differences design

Few studies have examined nonshared environmental risk factors for disordered eating, and none have done so using a longitudinal design. The current project used a longitudinal, monozygotic twin differences design to examine parent-child conflict as a nonshared environmental risk factor for disordered eating. Participants included 468 monozygotic female twins (234 pairs) from the Minnesota Twin Family Study, who completed surveys every 3 years from ages 11 to 17 years. Twin differences in disordered eating were assessed with the Total Score, Body Dissatisfaction, Weight Preoccupation, and Binge Eating subscales of the Minnesota Eating Behavior Survey. Differences in parent-child conflict were assessed with the Parental Environment Questionnaire. Cross-lagged models were used to examine longitudinal associations among these variables, controlling for within-age associations. Only the longitudinal association between twin differences in disordered eating at age 14 years and differences in parent-child conflict at age 17 years were significant; twin differences in disordered eating predicted later differences in parent-child conflict rather than the reverse. Findings suggest differences in parent-child conflict between genetically identical twins may be a consequence of, rather than a risk factor for, differences in disordered eating.

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.

Shared and unique genetic and environmental influences on binge eating and night eating: a Swedish twin study

We applied twin methodology to female and male twin pairs to further understand the nature of the relation between two behaviors associated with eating disorders-binge eating (BE) and night eating (NE) in an effort to determine the extent of overlap of genetic and environmental factors influencing liability to these behaviors. We calculated heritability estimates for males and females for each behavior and applied bivariate twin modeling to the female data to estimate the genetic and environmental correlation between these two traits. Data on BE and NE were derived from the Swedish Twin study of Adults: Genes and Environment (STAGE) of the Swedish Twin Registry (STR; N=11,604). Prevalence estimates revealed sex differences with females more likely to endorse BE and males more likely to endorse NE. In males, we were only able to estimate univariate heritabilities due to small sample sizes: The heritability for BE was 0.74 [95% CI=(0.36, 0.93)] and for NE was 0.44 [95% CI=(0.24, 0.61)]. The best fitting bivariate model for females included additive genetic and unique environmental factors as well as the genetic correlation between BE and NE. Heritability estimates were 0.70 [95% CI=(0.26, 0.77)] for BE and 0.35 [95% CI=(0.17, 0.52)] for NE. The genetic correlation, 0.66 [95% CI=(0.48, 0.96)] suggests considerable overlap in the genetic factors influencing liability to BE and NE. In females, there is considerable overlap in the genetic factors that contribute to these traits, but the incomplete overlap allows for the influence of independent genetic and environmental factors as well. BE and NE in females are therefore best conceptualized as related but not identical traits.