Pubertal timing and adolescent outcomes: investigating explanations for associations with a genetically informed design

BACKGROUND

Psychopathology and risky behaviors increase during adolescence, and understanding which adolescents are most at risk informs prevention and intervention efforts. Pubertal timing relative to same-sex, same-age peers is a known correlate of adolescent outcomes among both boys and girls. However, it remains unclear whether this relation is better explained by a plausible causal process or unobserved familial liability.

METHODS

We extended previous research by examining associations between pubertal timing in early adolescence (age 14) and outcomes in later adolescence (age 17) in a community sample of 2,510 twins (49% boys, 51% girls).

RESULTS

Earlier pubertal timing was associated with more substance use, risk behavior, internalizing and externalizing problems, and peer problems in later adolescence; these effects were small, consistent with previous literature. Follow-up co-twin control analyses indicated that within-twin-pair differences in pubertal timing were not associated with within-twin-pair differences in most adolescent outcomes after accounting for shared familial liability, suggesting that earlier pubertal timing and adolescent outcomes both reflect familial risk factors. Biometric models indicated that associations between earlier pubertal timing and negative adolescent outcomes were largely attributable to shared genetic liability.

CONCLUSIONS

Although earlier pubertal timing was associated with negative adolescent outcomes, our results suggests that these associations did not appear to be caused by earlier pubertal timing but were likely caused by shared genetic influences.

Arranging the fruit basket: A computational approach towards a better understanding of adolescents' diet-related social media communications

This study investigated the contents and linguistic styles that adolescents use in their dietary communications on social media. The main aim of the study was to describe adolescents' social media communication practices with regards to diet, in order to better understand dietary social influences and how to effectively intervene in them. The current study made use of an online communication dataset (N = 72,384 messages) of adolescents in primary and secondary school (N = 1038, 9-16 y/o). We analyzed the message content using tailor-made diet- and health-related dictionaries and LDA topic modeling. The linguistic style of the messages was investigated by assessing the sentiment and underlying psychological dimensions. Further, we used multivariate linear regressions to test how each message dimension was related to message liking, which was considered as an indicator of a message's influence potential regarding peers' dietary behaviors. The results confirmed that adolescents show a preference to discuss neutral-to-unhealthy dietary items most often. No association emerged between message content (i.e., message healthiness and topics) and the number of likes that a message received, while messages with more positive sentiment and higher subjectivity received slightly more likes. Also, our findings confirm that visual dietary content is more often liked than textual descriptions alone. The findings indicate that the content and the healthiness of a message does not explain its popularity among adolescents. Rather, the way how diet-related content is formulated (i.e., in a positive and subjective tone) emerged as a more important predictor for message liking.

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.

Structural brain correlates of eating pathology symptom dimensions: A systematic review

There has been an increasing interest in neurobiological correlates of psychopathology with a growing consensus that such research questions are best investigated through dimensional approaches to psychopathology. One area that has been noticeably understudied in this regard is eating pathology. Therefore, the goal of the current systematic review was to summarize research on structural brain correlates of symptom dimensions of eating-related pathology. Google Scholar and PubMed databases were searched following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Results suggest that restrained eating is associated with increased GMV (gray matter volume) in regions involved in emotional, visuo-spatial, attentional, and self-related processing. Disinhibitory eating is associated with increased GMV in regions involved in reward value of food-related stimuli and decreased GMV in regions involved in emotional/motivational processing. All told, results suggest that dimensions of eating pathology have differential neuroanatomical correlates potentially suggesting differences in neural pathways which has the potential to support future biologically-driven classification and treatment efforts.

E-Cigarette Dependence and Weight-Related Attitudes/Behaviors Associated With Eating Disorders in Adolescent Girls

Background: Although numerous motivations for vaping have been identified in adolescents, no study to date has examined a possible link between vaping and attitudes/behaviors that are associated with eating disorders in adolescent females. Examining this question in adolescent females is especially relevant given the higher prevalence of eating disorders in adolescent girls and women compared to adolescent boys and men. Methods: We recruited 299 girls (between 13 to 17 years old) via Facebook advertisement to complete a REDCap survey, which included the Electronic Cigarette Dependence Index (ECDI), Minnesota Eating Behavior Survey (MEBS), and demographic questions. Data were analyzed using nonparametric Spearman rank correlation test in R. Results: Electronic Cigarette Dependence Index (ECDI) scores were correlated with weight preoccupation (WP), binge eating (BE) and compensatory behavior (CB), but not body dissatisfaction (BD). The following were the results of Spearman correlation tests: (1) WP: rho = 0.13, p = 0.02; (2) BD: rho = 0.06, p = 0.28; (3) BE: rho = 0.15, p = 0.0095; (4) CB: rho = 0.021, p = 0.00027. Conclusion: The present study adds to the current literature examining motivations for e-cigarette use in adolescent girls. As eating disorders and e-cigarette dependence are significant public health concerns, our results highlight the need for intervention development.

Differences in genetic and environmental influences on body weight and shape concerns across pubertal development in females

The heritability of disordered eating increases during puberty; however, prior studies have largely examined a composite score of disordered eating, rather than specific symptoms. Body weight and shape concerns cut across all eating disorder diagnoses and are some of the strongest prospective risk factors for the development of eating disorders. Yet, little is known about potential developmental increases or decreases in genetic and environmental influences for these key symptoms. This study examined differences in genetic and environmental effects on a range of body weight and shape concerns during puberty and compared results to findings for overall levels of disordered eating symptoms. Participants were 926 same-sex female twins (ages 8-16) from the Michigan State University Twin Registry. Well-validated questionnaires were used to examine pubertal maturation, overall levels of disordered eating, and a range of cognitive body weight/shape constructs: body dissatisfaction, weight/shape concerns, and weight preoccupation. Findings for overall levels of disordered eating were very similar to those obtained in previous work, with significantly increased genetic effects in girls at more advanced pubertal development. Importantly, these same pubertal increases in genetic influences were observed for body dissatisfaction and weight/shape concerns. However, no pubertal moderation of genetic effects was observed for weight preoccupation; instead, pubertal moderation of nonshared and shared environmental effects was observed. Our findings point to differences in the extent to which genetic and environmental factors contribute to various cognitive body weight and shape symptoms during puberty.

The Role of Puberty and Ovarian Hormones in the Genetic Diathesis of Eating Disorders in Females

Puberty is a critical risk period for eating disorders (EDs). ED incidence increases across the pubertal period and becomes female predominant, and genetic influences on disordered eating significantly increase. Surges of ovarian hormones, particularly estrogen, may drive this increasing genetic effect for EDs in pubertal girls and contribute to differential phenotypic presentations beyond puberty. In this article, we explain phenotypic associations between puberty and disordered eating and present evidence showing underlying genetic and hormonal influence. Potential benefits of communicating roles of genetic influence to people with or at risk for EDs are also discussed.

Updates on Treatments for Adolescent Anorexia Nervosa

This article provides background information, descriptions, and evidential support for the more recent treatments for adolescents with anorexia nervosa, including family-based treatment, adolescent focused therapy, cognitive behavioral therapy, systemic family therapy, and psychopharmacologic treatments. At this time, family-based treatment has the best evidence of efficacy and cost-effectiveness. Future directions in treatment research for adolescent anorexia nervosa are discussed.

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.

Metacognition, emotional functioning and binge eating in adolescence: the moderation role of need to control thoughts

PURPOSE

Binge eating is predicted by emotion dysregulation and poor emotional awareness. Dysfunctional metacognition is also implied in several eating disorders, but research has not yet investigated the interactions among emotional and metacognitive processes involved in binge eating. The present study investigated the relation between metacognition and binge eating in a sample of adolescents, testing the interaction effect between the need to control thoughts and the lack of emotional awareness on binge eating.

METHODS

Participants were 804 adolescents (age range 15-20; 49.7% female), who completed self-report instruments assessing binge eating, emotion regulation, and metacognition.

RESULTS

Binge eating was predicted by gender, BMI, emotion dysregulation, lack of emotional awareness, and dysfunctional metacognition dimensions (cognitive confidence and need to control thoughts). An important moderating effect was found, whereby the relationship between binge eating and lack of emotional awareness was only significant for individuals with a high need to control thoughts.

CONCLUSIONS

Results described emotional and metacognitive functioning in binge eating adolescents, suggesting that the need to control thoughts is a risk factor, whereas good metacognitive competencies are protective from binge eating, even in presence of poor emotional awareness.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Gene-Environment Interplay in Child Eating Behaviors: What the Role of "Nature" Means for the Effects of "Nurture"

PURPOSE OF REVIEW

This narrative review describes the evidence for both genetic and environmental influences on child appetitive traits and suggests ways of thinking about how these interact and correlate to influence how a child eats.

RECENT FINDINGS

Emerging evidence from social network analysis, and from longitudinal studies questioning the direction of association between parent feeding behaviors and child obesity risk, suggest that children's genes may shape the environmental risk for obesity that they are exposed to. There is strong evidence that child appetitive traits are both heritable and shaped by the environment. Instead of thinking about how genetic and environmental factors operate independently on each appetitive trait, research needs to expand the current paradigm to examine how genes and environments interact and shape each other.

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.

The influence of maternal modeling on body image concerns and eating disturbances in preadolescent girls

Research suggests that mothers may influence the development of body image concerns and eating disturbances in their daughters by modeling negative body image beliefs and unhealthy eating behaviors. However, the causal nature of that mode of influence is yet to be established. This study implemented an experimental design to examine the impact of mothers' modeling of negative comments about their own appearance and diet on their daughters' body image concerns and eating behaviors. Participants were 8-12 year old girls and their mothers (N = 50). While viewing thin-ideal magazine advertisements with their daughter, mothers were instructed to make either negative comments about their own weight, shape, and diet or to make no appearance or diet related comments. Daughters' levels of body esteem, body satisfaction, and eating attitudes were assessed pre- and post-manipulation, and their actual eating habits were measured post-manipulation. Girls whose mothers had made self-critical comments about their own appearance and diet reported lower body esteem, lower body satisfaction, more problematic eating attitudes, and ate significantly fewer sweets than girls whose mothers had not made self-critical comments. These results have implications for disordered eating prevention programs, suggesting that greater emphasis be placed on discouraging negative modeling behaviors among mothers.

The significant effects of puberty on the genetic diathesis of binge eating in girls

OBJECTIVE

Recent data show significant phenotypic and genetic associations between ovarian hormones and binge eating in adulthood. Theories of hormonal risk focus on puberty and the possibility that hormone activation induces changes in genetic effects that then lead to differential risk for binge eating in postpuberty and adulthood. Although this theory is difficult to test in humans, an indirect test is to examine whether genetic influences on binge eating increase during the pubertal period in girls. Prior work has shown pubertal increases in genetic influences on overall disordered eating symptoms, but no study to date has examined binge eating. The present study was the first to examine these increases for binge eating.

METHODS

Participants included 1,568 female twins (aged 8-25 years) from the Michigan State University Twin Registry. Binge eating and pubertal development were assessed with self-report questionnaires.

RESULTS

Twin moderation models showed significant linear increases in genetic effects from prepuberty (5%) to postpuberty (42%), even after controlling for the effects of age and body mass index.

DISCUSSION

Results provide critical support for increased genetic influences on binge eating during puberty. Additional studies are needed to identify hormonal mechanisms and fully test contemporary models of ovarian hormone risk.

Sex Differences in Binge Eating: Gonadal Hormone Effects Across Development

Eating disorders are highly sexually differentiated disorders that exhibit a female predominance in risk. Most theories focus on psychosocial explanations to the exclusion of biological/genetic influences. The purpose of this descriptive review is to evaluate evidence from animal and human studies in support of gonadal hormone effects on sex differences in binge eating. Although research is in its nascent stages, findings suggest that increased prenatal testosterone exposure in males appears to protect against binge eating. Although pubertal testosterone may exert additional protective effects, the prenatal period is likely critical for the decreased risk observed in males. By contrast, studies indicate that, in females, it is the lack of prenatal testosterone coupled with the organizational effects of pubertal ovarian hormones that may lead to increased binge eating. Finally, twin data suggest that changes in genetic risk may underlie these hormone influences on sex differences across development.

Speaking of That: Terms to Avoid or Reconsider in the Eating Disorders Field

Inspired by an article on 50 terms that, in the interest of clarity in scientific reasoning and communication in psychology, psychiatry, and allied fields, "should be avoided or at most be used sparingly and only with explicit caveats,"(1) we propose a list of terms to avoid or think twice about before using when writing for the International Journal of Eating Disorders (IJED). Drawing upon our experience as reviewers or editors for the IJED, we generated an abridged list of such terms. For each term, we explain why it made our list and what alternatives we recommend. We hope that our list will contribute to improved clarity in scientific thinking about eating disorders, and that it will stimulate discussion of terms that may need to be reconsidered in our field's vocabulary to ensure the use of language that is respectful and sensitive to individuals who experience an eating disorder.

Does parental divorce moderate the heritability of body dissatisfaction? An extension of previous gene-environment interaction effects

OBJECTIVE

Previous research suggests that parental divorce moderates genetic influences on body dissatisfaction. Specifically, the heritability of body dissatisfaction is higher in children of divorced versus intact families, suggesting possible gene-environment interaction effects. However, prior research is limited to a single, self-reported measure of body dissatisfaction. The primary aim of this study was to examine whether these findings extend to a different dimension of body dissatisfaction: body image perceptions.

METHOD

Participants were 1,534 female twins from the Minnesota Twin Family Study, aged 16-20 years. The Body Rating Scale (BRS) was used to assess body image perceptions.

RESULTS

Although BRS scores were heritable in twins from divorced and intact families, the heritability estimates in the divorced group were not significantly greater than estimates in the intact group. However, there were differences in nonshared environmental effects, where the magnitude of these environmental influences was larger in the divorced as compared with the intact families.

DISCUSSION

Different dimensions of body dissatisfaction (i.e., negative self-evaluation versus body image perceptions) may interact with environmental risk, such as parental divorce, in discrete ways. Future research should examine this possibility and explore differential gene-environment interactions using diverse measures.

Changes in genetic risk for emotional eating across the menstrual cycle: a longitudinal study

BACKGROUND

Previous studies have shown significant within-person changes in binge eating and emotional eating across the menstrual cycle, with substantial increases in both phenotypes during post-ovulation. Increases in both estradiol and progesterone levels appear to account for these changes in phenotypic risk, possibly via increases in genetic effects. However, to date, no study has examined changes in genetic risk for binge phenotypes (or any other phenotype) across the menstrual cycle. The goal of the present study was to examine within-person changes in genetic risk for emotional eating scores across the menstrual cycle.

METHOD

Participants were 230 female twin pairs (460 twins) from the Michigan State University Twin Registry who completed daily measures of emotional eating for 45 consecutive days. Menstrual cycle phase was coded based on dates of menstrual bleeding and daily ovarian hormone levels.

RESULTS

Findings revealed important shifts in genetic and environmental influences, where estimates of genetic influences were two times higher in post- as compared with pre-ovulation. Surprisingly, pre-ovulation was marked by a predominance of environmental influences, including shared environmental effects which have not been previously detected for binge eating phenotypes in adulthood.

CONCLUSIONS

Our study was the first to examine within-person shifts in genetic and environmental influences on a behavioral phenotype across the menstrual cycle. Results highlight a potentially critical role for these shifts in risk for emotional eating across the menstrual cycle and underscore the need for additional, large-scale studies to identify the genetic and environmental factors contributing to menstrual cycle effects.

Parental and Child Characteristics Related to Early-Onset Disordered Eating: A Systematic Review

LEARNING OBJECTIVES

After participating in this activity, learners should be better able to: Evaluate the evidence regarding parental and child characteristics related to early-onset disordered eating.

ABSTRACT

Eating disorders are rare in children, but disordered eating is common. Understanding the phenomenology of disordered eating in childhood can aid prevention of full-blown eating disorders. The purpose of this review is to systematically extract and synthesize the evidence on parental and child characteristics related to early-onset disordered eating. Systematic searches were conducted in PubMED/MEDLINE, EMBASE, and PsycInfo using the following search terms: eating disorder, disordered eating, problem eating, anorexia nervosa, bulimia nervosa, binge eating, child, preadolescent, and early onset. Studies published from 1990 to 2013 addressing parental and child characteristics of disordered eating in children aged 6 to 12 years were eligible for inclusion. The search was restricted to studies with cross-sectional, case-control, or longitudinal designs, studies in English, and with abstracts available. Forty-four studies fit these criteria. Most studies were based on community samples with a cross-sectional design. The included studies varied considerably in size, instruments used to assess early-onset disordered eating, and parental and child characteristics investigated. Important determinants included the following: higher body weight, previously reported disordered eating, body dissatisfaction, depression, parental disordered eating, and parental comments/concerns about child's weight and eating. The findings were inconsistent for sex, age, socioeconomic status, ethnicity, self-esteem/worth, and parental body weight. In conclusion, characteristics related to early-onset disordered eating have mainly been explored with a cross-sectional design. Full understanding of causal pathways will require good-quality longitudinal studies designed to address the influence of parental eating behaviors, mental and physical health, family interactions, and child growth patterns.

Research Review: What we have learned about the causes of eating disorders - a synthesis of sociocultural, psychological, and biological research

BACKGROUND

Eating disorders are severe psychiatric disorders with a complex etiology involving transactions among sociocultural, psychological, and biological influences. Most research and reviews, however, focus on only one level of analysis. To address this gap, we provide a qualitative review and summary using an integrative biopsychosocial approach.

METHODS

We selected variables for which there were available data using integrative methodologies (e.g., twin studies, gene-environment interactions) and/or data at the biological and behavioral level (e.g., neuroimaging). Factors that met these inclusion criteria were idealization of thinness, negative emotionality, perfectionism, negative urgency, inhibitory control, cognitive inflexibility, serotonin, dopamine, ovarian hormones. Literature searches were conducted using PubMed. Variables were classified as risk factors or correlates of eating disorder diagnoses and disordered eating symptoms using Kraemer et al.'s (1997) criteria.

FINDINGS

Sociocultural idealization of thinness variables (media exposure, pressures for thinness, thin-ideal internalization, thinness expectancies) and personality traits (negative emotionality, perfectionism, negative urgency) attained 'risk status' for eating disorders and/or disordered eating symptoms. Other factors were identified as correlates of eating pathology or were not classified given limited data. Effect sizes for risk factors and correlates were generally small-to-moderate in magnitude.

CONCLUSIONS

Multiple biopsychosocial influences are implicated in eating disorders and/or disordered eating symptoms and several can now be considered established risk factors. Data suggest that psychological and environmental factors interact with and influence the expression of genetic risk to cause eating pathology. Additional studies that examine risk variables across multiple levels of analysis and that consider specific transactional processes amongst variables are needed to further elucidate the intersection of sociocultural, psychological, and biological influences on eating disorders.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

DISCUSSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The effects of ovarian hormones and emotional eating on changes in weight preoccupation across the menstrual cycle

OBJECTIVE

Previous research has shown that fluctuations in ovarian hormones (i.e., estradiol and progesterone) predict the changes in binge eating and emotional eating across the menstrual cycle. However, the extent to which other eating disorder symptoms fluctuate across the menstrual cycle and are influenced by ovarian hormones remains largely unknown. This study sought to examine whether the levels of weight preoccupation vary across the menstrual cycle and whether the changes in ovarian hormones and/or other factors (i.e., emotional eating and negative affect) account for menstrual cycle fluctuations in this eating disorder phenotype.

METHOD

For 45 consecutive days, 352 women (age, 15-25 years) provided daily ratings of weight preoccupation, negative affect, and emotional eating. Saliva samples were also collected on a daily basis and assayed for levels of estradiol and progesterone using enzyme immunoassay techniques.

RESULTS

Weight preoccupation varied significantly across the menstrual cycle, with the highest levels in the premenstrual and menstrual phases. However, ovarian hormones did not account for within-person changes in weight preoccupation across the menstrual cycle. Instead, the most significant predictor of menstrual cycle changes in weight preoccupation was the change in emotional eating.

DISCUSSION

Fluctuations in weight preoccupation across the menstrual cycle appear to be influenced primarily by emotional eating rather than ovarian hormones. Future research should continue to examine the relationships among ovarian hormones, weight preoccupation, emotional eating, and other core eating disorder symptoms (e.g., body dissatisfaction, compensatory behaviors) in an effort to more fully understand the role of these biological and behavioral factors for the full spectrum of eating pathology.

Practice parameter for the assessment and treatment of children and adolescents with eating disorders

This Practice Parameter reviews evidence-based practices for the evaluation and treatment of eating disorders in children and adolescents. Where empirical support is limited, clinical consensus opinion is used to supplement systematic data review. The Parameter focuses on the phenomenology of eating disorders, comorbidity of eating disorders with other psychiatric and medical disorders, and treatment in children and adolescents. Because the database related to eating disorders in younger patients is limited, relevant literature drawn from adult studies is included in the discussion.

Genetic and environmental influences on thin-ideal internalization across puberty and preadolescent, adolescent, and young adult development

OBJECTIVE

Mean-levels of thin-ideal internalization increase during adolescence and pubertal development, but it is unknown whether these phenotypic changes correspond to developmental changes in etiological (i.e., genetic and environmental) risk. Given the limited knowledge on risk for thin-ideal internalization, research is needed to guide the identification of specific types of risk factors during critical developmental periods. The present twin study examined genetic and environmental influences on thin-ideal internalization across adolescent and pubertal development.

METHOD

Participants were 1,064 female twins (ages 8-25 years) from the Michigan State University Twin Registry. Thin-ideal internalization and pubertal development were assessed using self-report questionnaires. Twin moderation models were used to examine if age and/or pubertal development moderate genetic and environmental influences on thin-ideal internalization.

RESULTS

Phenotypic analyses indicated significant increases in thin-ideal internalization across age and pubertal development. Twin models suggested no significant differences in etiologic effects across development. Nonshared environmental influences were most important in the etiology of thin-ideal internalization, with genetic, shared environmental, and nonshared environmental accounting for approximately 8%, 15%, and 72%, respectively, of the total variance.

DISCUSSION

Despite mean-level increases in thin-ideal internalization across development, the relative influence of genetic versus environmental risk did not differ significantly across age or pubertal groups. The majority of variance in thin-ideal internalization was accounted for by environmental factors, suggesting that mean-level increases in thin-ideal internalization may reflect increases in the magnitude/strength of environmental risk across this period. Replication is needed, particularly with longitudinal designs that assess thin-ideal internalization across key developmental phases.

Developmental trajectories of disordered eating from early adolescence to young adulthood: a longitudinal study

OBJECTIVE

Research examining changes in eating disorder symptoms across adolescence suggests an increase in disordered eating from early to late adolescence. However, relevant studies have largely been cross-sectional in nature and most have not examined the changes in the attitudinal symptoms of eating disorders (e.g., weight concerns). This longitudinal study aimed to address gaps in the available data by examining the developmental trajectories of disordered eating in females from preadolescence into young adulthood.

METHOD

Participants were 745 same-sex female twins from the Minnesota Twin Family Study. Disordered eating was assessed using the Total Score, Body Dissatisfaction subscale, Weight Preoccupation subscale, and a combined Binge Eating and Compensatory Behavior subscale from the Minnesota Eating Behavior Survey assessed at the ages of 11, 14, 18, 21, and 25. Several latent growth models were fit to the data to identify the trajectory that most accurately captures the changes in disordered eating symptoms from 11 to 25 years.

RESULTS

The best-fitting models for overall levels of disordered eating, body dissatisfaction, and weight preoccupation showed an increase in from 11 through 25 years. In contrast, bulimic behaviors increased to age of 18 and then stabilized to age of 25.

DISCUSSION

The findings expanded upon extant research by investigating longitudinal, symptom specific, within-person changes and showing an increase in cognitive symptoms into young adulthood and the stability of disordered eating behaviors past late adolescence.

Behavior Genetics and the Within-Person Variability of Daily Interpersonal Styles: The Heritability of Flux, Spin and Pulse

A classical twin study was used to estimate the magnitude of genetic and environmental influences on four measurements of within-person variability: dominance flux, warmth flux, spin and pulse. Flux refers to the variability of an individual's interpersonal dominance and warmth. Spin measures changes in the tone of interpersonal styles and pulse measures changes in the intensity of interpersonal styles. Daily reports of interpersonal styles were collected from 494 same-sex female twins (142 monozygotic pairs and 105 dizygotic pairs) over 45 days. For dominance flux, warmth flux, and spin, genetic effects accounted for a larger proportion of variance (37%, 24%, and 30%, respectively) than shared environmental effects (14%, 13%, 0%, respectively), with the remaining variance due to the non-shared environment (62%, 50%, 70% respectively). Pulse appeared to be primarily influenced by the non-shared environment, although conclusions about the contribution of familial influences were difficult to draw from this study.

Body-esteem of pupils who attended single-sex versus mixed-sex schools: a cross-sectional study of intrasexual competition and peer victimization

In intrasexual competition (competition for reproductive resources), bullying can be viewed as a tool to devalue competitors, gain a high status and a powerful, dominant position in the peer group which may lead to beneficial gains such as access to potential romantic partners. This study investigated the relationship between intrasexual competition, bullying victimization and body-esteem, in single-sex versus mixed-sex schools. 420 participants completed a body-esteem scale, a retrospective bullying questionnaire, and intrasexual competition scales. Our results showed that relational victimization was associated with low body-esteem for both females and males. Females in single-sex schools experienced higher intrasexual competition which in turn was associated with their body-esteem directly and indirectly via relational victimization. In males, intrasexual competition was indirectly associated with body-esteem via relational victimization. Interventions to improve body esteem may focus on reducing intrasexual competition and peer victimization.

Environmental factors associated with disordered weight-control behaviours among youth: a systematic review

OBJECTIVE

Environmental factors may be very important in the development of disordered weight-control behaviours (DWCB) among youth, yet no study to date has conducted a review that synthesizes these findings. The purpose of the present study was to systematically review existing literature on environmental influences on DWCB among youth and to identify conceptual and methodological gaps in the literature.

DESIGN

Systematic review.

SETTING

Studies were identified through a systematic search using PubMed, PsycINFO, Google Scholar and secondary references. Inclusion criteria included observational studies published in peer-reviewed journals from 1994 to 2012 that examined environmental exposure(s) associated with DWCB among youth.

SUBJECTS

Ninety-three studies, the majority of which utilized a cross-sectional design (75 %; n 70), were identified. Longitudinal studies' follow-up time ranged from 8 months to 10 years.

RESULTS

Parental, peer and media influences have been extensively studied as factors associated with DWCB among youth. Fewer studies have examined behavioural settings (i.e. homes, schools, neighbourhoods) or sectors of influence other than the media on DWCB. No studies utilized multilevel methods to parse out environmental influences on DWCB. Most studies (69 %, n 64) did not explicitly utilize a theory or model to guide the research.

CONCLUSIONS

Findings indicate that exploring a wider range of environmental influences on DWCB, specifically behavioural settings and sectors of influence, using diverse study samples and multilevel methodology is needed to advance the field and to inform the design of comprehensive prevention programmes that target DWCB and other weight-related behaviours.

Ovarian Hormone Influences on Dysregulated Eating: A Comparison of Associations in Women with versus without Binge Episodes

Changes in ovarian hormones predict changes in emotional eating across the menstrual cycle. However, prior studies have not examined whether the nature of associations varies across dysregulated eating severity. The current study determined whether the strength and/or nature of hormone/dysregulated eating associations differ based on the presence of clinically diagnosed binge episodes (BEs). Participants included 28 women with BEs and 417 women without BEs who provided salivary hormone samples, ratings of emotional eating, and BE frequency for 45 days. Results revealed stronger associations between dysregulated eating and ovarian hormones in women with BEs as compared to women without BEs. The nature of associations also differed, as progesterone moderated the effects of lower estradiol levels on dysregulated eating in women with BEs only. Although hormone/dysregulated eating associations are present across the spectrum of pathology, the nature of associations may vary in ways that have implications for etiological models and treatment.

Sex differences in binge eating patterns in male and female adult rats

OBJECTIVE

Several efforts are underway to model binge eating in animals in order to advance neurobiological models of risk. However, knowledge of sex differences in these models is currently lacking. The goal of the present study was to examine sex differences in binge eating phenotypes using a well-established rodent model (i.e., the binge eating resistant/binge eating prone model).

METHOD

Thirty male and 30 female adult Sprague-Dawley rats were exposed to feeding tests consisting of intermittent access to palatable food (PF). Rats were then categorized as binge eating prone (BEP) based on the amount and consistency of PF consumption across tests.

RESULTS

Across multiple methods for BEP classification, rates of BEP phenotypes were two to six times higher in female than male rats.

DISCUSSION

Findings provide support for sex differences in rodent models of binge eating and highlight the promise of the BER/BEP model for understanding neurobiological mechanisms underlying sex differences in risk.

Child food neophobia is heritable, associated with less compliant eating, and moderates familial resemblance for BMI

OBJECTIVE

The heritability of food neophobia, the tendency to avoid new foods, was tested in 4-7-year-old twins. We also examined whether food neophobia is associated with parent-child feeding relations or child body fat.

DESIGN AND METHODS

66 same-sex twin pairs, including 37 monozygotic (MZ) and 29 dizygotic (DZ) pairs were studied. Food neophobia was assessed by parent questionnaire (Child Food Neophobia Scale, CFNS), as were child-feeding practices and "division of responsibility" feeding relations. Child anthropometry and percent body fat were directly measured.

RESULTS

MZ and DZ twin pair correlations for food neophobia were r = 0.71 and r = -0.01, respectively: heritability= 72%. Greater food neophobia was associated with reduced child eating compliance of prompted foods (P < 0.001) reduced eating compliance of initially refused foods (P < 0.001), and--among girls only--fewer parental food demands (P = 0.01). Interestingly, the correlation between maternal BMI and child BMI z-score was significant only for children high (P = 0.03), but not low (P = 0.55), in food neophobia.

CONCLUSION

Child food neophobia, a highly heritable trait previously linked to emotionality, was associated with less compliant parent-child feeding relations. Strategies to combat food neophobia and foster more harmonious feeding relationships may have a role in obesity prevention.

Phenotype-environment correlations in longitudinal twin models

Gene-environment correlation (rGE) exists both within and between families. Between families, accumulating rGE has been used to explain dramatic changes in phenotypic means over time. The Dickens and Flynn model of increases in cognitive ability over generational time, for example, suggests that small changes in phenotype can lead to subsequent reallocation of environmental resources. This process sets up a reciprocal feedback loop between phenotype and environment, producing accumulating rGE that can cause large changes in the mean of ability, even though ability remains highly heritable in cross-sectional data. We report simulations suggesting that similar processes may operate within twin and sibling pairs. Especially in dizygotic twins and siblings, small differences in phenotype can become associated with reallocations of environmental resources within families. We show that phenotype-environment effects can account for age-related increases in rGE, rapid differentiation of siblings raised together, and widely reported increases in the heritability of behavior during childhood and adolescence.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

An examination of the representativeness assumption for twin studies of eating pathology and internalizing symptoms

Little research has investigated whether the twin representativeness assumption (that results from twin research generalize to singletons) holds for eating pathology and internalizing symptoms. This study compared disordered eating, depression, and anxiety among young adult female twins versus singletons. Participants included 292 twins and 997 singletons in three samples. Questionnaires included the Minnesota Eating Behavior Survey, Eating Disorder Examination Questionnaire, Beck Depression Inventory, and State-Trait Anxiety Inventory. We examined mean differences between twins' and singletons' scores, after adjusting for age, body mass index, and ethnicity. We found statistically significant mean differences on psychopathology, with twins reporting less disordered eating and internalizing symptoms compared with singletons. Effect sizes of these mean differences were small to moderate. Our results suggest that twins report less disordered eating and internalizing symptoms than singletons, which, combined with the generally small effect sizes, indicate that results from twin samples generalize to singletons.

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.

The dysregulated cluster in personality profiling research: longitudinal stability and associations with bulimic behaviors and correlates

Among cluster analytic studies of the personality profiles associated with bulimia nervosa, a group of individuals characterized by emotional lability and behavioral dysregulation (i.e., a dysregulated cluster) has emerged most consistently. However, previous studies have all been cross-sectional and mostly used clinical samples. This study aimed to replicate associations between the dysregulated personality cluster and bulimic symptoms and related characteristics using a longitudinal, population-based sample. Participants were females assessed at ages 17 and 25 from the Minnesota Twin Family Study, clustered based on their personality traits. The Dysregulated cluster was successfully identified at both time points and was more stable across time than either the Resilient or Sensation Seeking clusters. Rates of bulimic symptoms and related behaviors (e.g., alcohol use problems) were also highest in the dysregulated group. Findings suggest that the dysregulated cluster is a relatively stable and robust profile that is associated with bulimic symptoms.

Inpatients with severe anorexia nervosa and their siblings: non-shared experiences and family functioning

OBJECTIVES

The aims of this study were the following: to identify perceptions of patients with anorexia nervosa (AN) and their siblings regarding differential experiences within and external to the family including sibling interactions, parental treatment, relationships with peers and events that are unique to each sibling; (2) to compare how patients and their siblings perceive eating disorder symptoms, parental affection/control, social support and stigma; and (3) to test associations with family functioning for patients with AN and their siblings.

METHOD

A total of 26 patients paired with their siblings were recruited from an Eating Disorder Program and administered standardized instruments measuring different experiences within and external to the family, the impact of eating disorder behaviours, stigma, social support and family functioning.

RESULTS

Patients rated high on the differential experience of jealousy in contrast to their siblings. Patients scored higher than their siblings on eating symptoms, whereas siblings scored higher on social support. The impact of AN on the family, stigma towards the individual and family, and social support accounted for 37% of the variance in family functioning from the sibling perspective after controlling for age and gender. Of these variables, impact of AN on the family made the largest contribution.

DISCUSSION

Family-based and sibling-based interventions that aim to reduce the effects of the illness on the sibling relationship and the family are recommended.

Bulimic behaviors and alcohol use: shared genetic influences

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

The Michigan State University Twin Registry (MSUTR): an update

The primary aim of the Michigan State University Twin Registry (MSUTR) is on understanding developmental changes in genetic, environmental, and neurobiological influences on internalizing and externalizing disorders, with antisocial behavior and disordered eating representing our particular areas of interest. The MSUTR has two broad components: a large-scale, population-based registry of child, adolescent, and adult twins and their families (current N ~20,000) and a series of more focused and in-depth studies drawn from the registry (current N ~4,000). Participants in the population-based registry complete a family health and demographic questionnaire via mail. Families are then recruited for one or more of the intensive, in-person studies from the population-based registry based on their answers to relevant items in the registry questionnaire. These in-person assessments target a variety of biological, genetic, and environmental phenotypes, including multi-informant measures of psychiatric and behavioral phenotypes, census and neighborhood informant reports of twin neighborhood characteristics, buccal swab and salivary DNA samples, assays of adolescent and adult steroid hormone levels, and/or videotaped interactions of child twin families. This article provides an overview of the MSUTR and describes current and future research directions.

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.

Age-Related Changes in Heritability of Behavioral Phenotypes Over Adolescence and Young Adulthood: A Meta-Analysis

The relative proportions of genetic and environmental variance in behavioral measures have been studied extensively. A growing body of literature has examined changes in heritability measures over time, but we are unaware of any prior efforts to assess developmental heritability changes for multiple behavioral phenotypes using multiple data sources. We have chosen to explore the proportional genetic influences on a variety of behaviors during the genetically and environmentally labile adolescent and young adult years. This meta-analysis examined 8 behavioral domains and incorporated only primary research articles reporting two or more heritability time points in order to minimize the age-to-age error variability. Linear regression analyses revealed significant cross-time heritability increases for externalizing behaviors, anxiety symptoms, depressive symptoms, IQ, and social attitudes and nonsignificant increases for alcohol consumption, and nicotine initiation, but no evidence of heritability changes for attention-deficit/hyperactivity disorder. A variety of mechanisms may underlie these findings including the rising importance of active genotype-environment correlation, an increase in gene expression, or proportional reductions in environmental variance. Additional longitudinal studies and the inclusion of measures of total variance in primary research reports will aid in distinguishing between these possibilities. Further studies exploring heritability changes beyond young adulthood would also benefit our understanding of factors influencing heritability of behavioral traits over the lifespan.

A twin study of self-regulatory eating in early childhood: estimates of genetic and environmental influence, and measurement considerations

OBJECTIVE

Children differ greatly in their ability to self-regulate food intake for reasons that are poorly understood. This laboratory-based twin study tested the genetic and environmental contributions to self-regulatory eating and body fat in early childhood.

METHODS

A total of 69 4-7 year-old same-sex twin pairs, including 40 monozygotic and 29 dizygotic pairs, were studied. Self-regulatory eating was operationalized as the percentage compensation index (COMPX%), assessed by a 'preload' challenge in which lunch intake was measured following a low- (3 kcal) or high-calorie (159 kcal) drink. Body fat indexes also were measured. The familial association for COMPX% was estimated by an intraclass correlation, and biometric analyses estimated heritability.

RESULTS

Children ate more at lunch following the low- compared with high-energy preload (P<0.001), although variability in COMPX% was considerable. Compensation was significantly poorer among African American and Hispanic compared with European American children, and among girls compared with boys. There was a familial association for self-regulatory eating (ρ = 0.23, P = 0.03) but no significant genetic component. In all, 22% of the variance in COMPX% was due to shared environmental 'household' factors, with the remaining variance attributable to child-specific 'unique' or 'random' environments. Poorer self-regulatory eating was associated with greater percent body fat (r = -0.21, P = 0.04).

CONCLUSIONS

Self-regulatory eating was influenced by environmental factors, especially those differing among siblings. The absence of a significant genetic effect may reflect the age of the sample or could be artifactual due to measurement issues that need to be considered in future studies.

Association between co-twin sex and eating disorders in opposite sex twin pairs: evaluations in North American, Norwegian, and Swedish samples

OBJECTIVE

These three studies examined the hypothesis that prenatal exposure to sex hormones influences twins' risk for eating disorders based on co-twin sex, such that individuals with a female co-twin would be more likely than individuals with a male co-twin to meet diagnostic criteria for an eating disorder.

METHODS

Male and female twins from the United States (N=2607), Norway (N=2796) and Sweden (N=16,458) with known co-twin sex and zygosity were assessed for eating disorders.

RESULTS

In the U.S. and Swedish samples, sex was significantly associated with eating disorder diagnoses, and although co-twin sex was not associated with eating disorders overall, it was associated with broadly defined bulimia nervosa in the Swedish sample. The effects for bulimia were not sustained when monozygotic twins were excluded, suggesting that the effects of prenatal sex hormones play a minor role in influencing eating disorders. Sex and co-twin sex were not associated with eating disorders in the Norwegian sample.

CONCLUSION

The prenatal sex hormone hypothesis, which proposes that prenatal hormone exposure is associated with later eating disorder symptomatology, was not supported in these three population-based twin samples.

Genetic Influences on Adolescent Eating Habits

Behavioral genetic research shows that variation in eating habits and food consumption is due to genetic and environmental factors. The current study extends this line of research by examining the genetic contribution to adolescent eating habits. Analysis of sibling pairs drawn from the National Longitudinal Study of Adolescent Health (Add Health) revealed significant genetic influences on variance in an unhealthy eating habits scale ( h2 = .42), a healthy eating habits scale ( h2 = .51), the number of meals eaten at a fast-food restaurant ( h2 = .33), and the total number of meals eaten per week ( h2 = .26). Most of the remaining variance was due to nonshared environmental factors. Additional analyses conducted separately for males and females revealed a similar pattern of findings. The authors note the limitations of the study and offer suggestions for future research.

Personality development characteristics of women with anorexia nervosa, their healthy siblings and healthy controls: What prevents and what relates to psychopathology?

This exploratory study assessed attachment and personality in anorexic women, non-affected siblings, and healthy controls, examining correlations with psychopathology. Thirty-eight anorexic subjects (31 females), thirty-one siblings (22 females), and fifty controls (35 females) participated. Personality development characteristics were assessed using the Attachment Style Questionnaire (ASQ), Temperament and Character Inventory (TCI), Eating Disorders Inventory (EDI-2), Symptom Checklist-90 (SCL-90), and other inventories for clinical assessment of EDs. Both anorexic probands and their siblings described lower maternal care and higher maternal overprotection than did controls. Healthy siblings were more similar to controls, but had lower scores than either controls or affected siblings on preoccupation with relationships (P<0.005) and higher scores than controls on self-transcendence (P<0.015) and obsessive-compulsive traits (P<0.025). Logistic regression indicated that need for approval, persistence, resourcefulness, self-transcendence, state anger, pursuit of thinness, interpersonal distrust, social insecurity, and binge eating differentiated anorexic probands from siblings. The need for approval was related to several psychopathological characteristics. Low preoccupation with relationships, low need for approval, and high self-transcendence may have protected siblings from family and environmental stressors. High need for approval was independently related to psychopathological traits in anorexic siblings. Implications for prevention and treatment are discussed.