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1.  Ovarian Hormones and Emotional Eating Associations across the Menstrual Cycle: An Examination of the Potential Moderating Effects of Body Mass Index and Dietary Restraint 
Objective
Associations between within-person changes in ovarian hormones and dysregulated eating (binge eating, emotional eating) have been observed across the menstrual cycle. However, studies have not examined moderators that may contribute to differential associations between individuals. We investigated body-weight regulation variables (body mass index (BMI), dietary restraint) that have theoretical relevance by virtue of their associations with both phenotypes.
Method
Women (N = 196) provided emotional eating ratings and saliva samples for 45 days. BMI and restraint were assessed at three time-points and averaged.
Results
Results showed significant estradiol × progesterone interactions in the prediction of within-subject changes in emotional eating. Neither BMI nor restraint moderated these relationships, although a trend-level dietary restraint × estradiol interaction was observed where estradiol’s effects were enhanced in high restraint scorers.
Conclusions
Findings confirm a role for hormones in changes in emotional eating and suggest that restraint might enhance hormone effects in severe groups.
doi:10.1002/eat.22084
PMCID: PMC3600109  PMID: 23315657
2.  Individual Differences in the Relationship between Ovarian Hormones and Emotional Eating Across the Menstrual Cycle: A Role for Personality? 
Eating behaviors  2013;14(2):161-166.
Within-person changes in estradiol and progesterone predict changes in binge eating tendencies across the menstrual cycle. However, all women have menstrual-cycle fluctuations in hormones, but few experience binge eating. Personality traits may be critical individual difference factors that influence who will engage in emotional eating in the presence of a vulnerable hormonal environment. Women (N=239) provided self-reports of emotional eating and saliva samples for hormone measurement for 45 consecutive days. Negative urgency and negative emotionality were measured once and were examined as moderators of hormone-emotional eating associations. Consistent with prior research, within-person changes in the interaction between estradiol and progesterone predicted emotional eating. Neither negative urgency nor negative emotionality interacted with changes in estradiol and progesterone to predict changes in emotional eating. Additional factors, other than the two personality traits examined, may account for individual differences in within-person associations between hormones and emotional eating.
doi:10.1016/j.eatbeh.2013.02.007
PMCID: PMC3618657  PMID: 23557813
ovarian hormones; personality; negative urgency; eating disorders; emotional eating
3.  Binge Eating Proneness Emerges during Puberty in Female Rats: A Longitudinal Study 
Journal of abnormal psychology  2011;120(4):948-955.
Puberty is a critical risk period for binge eating and eating disorders characterized by binge eating. Previous research focused almost entirely on psychosocial risk factors during puberty to the relative exclusion of biological influences. The current study addressed this gap by examining the emergence of binge eating during puberty in a rat model. We predicted that there would be minimal differences in binge eating proneness during pre-early puberty, but significant differences would emerge during puberty. Two independent samples of female Sprague-Dawley rats (n = 30 and n = 36) were followed longitudinally across pre-early puberty, mid-late puberty, and adulthood. Binge eating proneness was defined using the binge eating resistant (BER)/binge eating prone (BEP) model of binge eating that identifies BER and BEP rats in adulthood. Across two samples of rats, binge eating proneness emerged during puberty. Mixed linear models showed little difference in palatable food intake between BER and BEP rats during pre-early puberty, but significant group differences emerged during mid-late puberty and adulthood. Group differences could not be accounted for by changes in non-palatable food intake or body weight. Similar to patterns in humans, individual differences in binge eating emerge during puberty in female rats. Findings provide strong confirming evidence for the importance of biological risk factors in developmental trajectories of binge eating risk across adolescence.
doi:10.1037/a0023600
PMCID: PMC3697134  PMID: 21574664
binge eating; puberty; animal models; bulimia nervosa; eating disorders
4.  Temporal Sequence of Comorbid Alcohol Use Disorder and Anorexia Nervosa 
Addictive behaviors  2012;38(3):1704-1709.
Women with eating disorders have a significantly higher prevalence of substance use disorders than the general population. The goal of the current study was to assess the temporal pattern of comorbid anorexia nervosa (AN) and alcohol use disorder (AUD) and the impact this ordering has on symptomatology and associated features. Women were placed into one of three groups based on the presence or absence of comorbid AUD and the order of AN and AUD onset in those with both disorders: (1) AN Only, (2) AN First, and (3) AUD First. The groups were compared on psychological symptoms and personality characteristics often associated with AN, AUD, or both using general linear models. Twenty-one percent of women (n = 161) with AN reported a history of AUD with 115 reporting AN onset first and 35 reporting AUD onset first. Women with binge-eating and/or purging type AN were significantly more likely to have AUD. In general, differences were found only between women with AN Only and women with AN and AUD regardless of order of emergence. Women with AN and AUD had higher impulsivity scores and higher prevalence of depression and borderline personality disorder than women with AN Only. Women with AN First scored higher on traits commonly associated with AN, whereas women with comorbid AN and AUD displayed elevations in traits more commonly associated with AUD. Results do not indicate a distinct pattern of symptomatology in comorbid AN and AUD based on the temporal sequence of the disorders.
doi:10.1016/j.addbeh.2012.10.005
PMCID: PMC3558554  PMID: 23254222
anorexia nervosa; alcohol use disorder; comorbidity; age of onset
5.  Etiological Contributions to the Covariation Between Children’s Perceptions of Inter-parental Conflict and Child Behavioral Problems 
Prior work has suggested that inter-parental conflict likely plays an etiological role in child behavior problems. However, family-level measurement of inter-parental conflict in most traditional child twin studies has made it difficult to tease apart the specific causal mechanisms underlying this association. The Children’s Perception of Inter-parental Conflict scale (CPIC) provides a child-specific measurement tool for examining these questions, as its subscales tap multiple dimensions of conflict assessed from the child’s (rather than the parent’s) perspective. The current study examined (1) the degree of genetic and environmental influence on each of the CPIC subscales, and (2) etiological contributions to the covariation between the CPIC scales and parental reports of child behavioral problems. The CPIC was completed by 1,200 child twins (aged 6-11 years) from the Michigan State University Twin Registry (MSUTR). Parents completed the Child Behavior Checklist (CBCL) to assess child internalizing and externalizing behavior problems. Multivariate models were examined to evaluate the relative contributions of genetic and environmental factors to both the CPIC scales and to their overlap with child behavioral outcomes. Modeling results indicated no significant moderation of sex or age. Significant environmental overlap emerged between the CPIC conflict properties scale and child internalizing and externalizing problems. By contrast, significant genetic correlations emerged between the CPIC self-blame scale and externalizing problems as well as between the CPIC threat scale and internalizing problems. Overall, findings suggest that the subscales of the CPIC are somewhat etiologically diverse and may provide a useful tool for future investigations of possible gene-environment interplay.
doi:10.1007/s10802-012-9679-7
PMCID: PMC3543475  PMID: 22996155
inter-parental conflict; genetic; environment; twins; child behavior problems; etiology
6.  The Interactive Effects of Estrogen and Progesterone on Changes in Emotional Eating Across the Menstrual Cycle 
Journal of abnormal psychology  2012;122(1):131-137.
Studies suggest that within-person changes in estrogen and progesterone predict changes in binge eating across the menstrual cycle. However, samples have been extremely small (maximum N = 9), and analyses have not examined the interactive effects of hormones that are critical for changes in food intake in animals. The aims of the current study were to examine ovarian hormone interactions in the prediction of within-subject changes in emotional eating in the largest sample of women to date (N = 196). Participants provided daily ratings of emotional eating and saliva samples for hormone measurement for 45 consecutive days. Results confirmed that changes in ovarian hormones predict changes in emotional eating across the menstrual cycle, with a significant estradiol x progesterone interaction. Emotional eating scores were highest during the mid-luteal phase, when progesterone peaks and estradiol demonstrates a secondary peak. Findings extend previous work by highlighting significant interactions between estrogen and progesterone that explain mid-luteal increases in emotional eating. Future work should explore mechanisms (e.g., gene-hormone interactions) that contribute to both within- and between-subject differences in emotional eating.
doi:10.1037/a0029524
PMCID: PMC3570621  PMID: 22889242
7.  A genome-wide association study of anorexia nervosa 
Boraska, Vesna | Franklin, Christopher S | Floyd, James AB | Thornton, Laura M | Huckins, Laura M | Southam, Lorraine | Rayner, N William | Tachmazidou, Ioanna | Klump, Kelly L | Treasure, Janet | Lewis, Cathryn M | Schmidt, Ulrike | Tozzi, Federica | Kiezebrink, Kirsty | Hebebrand, Johannes | Gorwood, Philip | Adan, Roger AH | Kas, Martien JH | Favaro, Angela | Santonastaso, Paolo | Fernández-Aranda, Fernando | Gratacos, Monica | Rybakowski, Filip | Dmitrzak-Weglarz, Monika | Kaprio, Jaakko | Keski-Rahkonen, Anna | Raevuori, Anu | Van Furth, Eric F | Slof-Op t Landt, Margarita CT | Hudson, James I | Reichborn-Kjennerud, Ted | Knudsen, Gun Peggy S | Monteleone, Palmiero | Kaplan, Allan S | Karwautz, Andreas | Hakonarson, Hakon | Berrettini, Wade H | Guo, Yiran | Li, Dong | Schork, Nicholas J. | Komaki, Gen | Ando, Tetsuya | Inoko, Hidetoshi | Esko, Tõnu | Fischer, Krista | Männik, Katrin | Metspalu, Andres | Baker, Jessica H | Cone, Roger D | Dackor, Jennifer | DeSocio, Janiece E | Hilliard, Christopher E | O’Toole, Julie K | Pantel, Jacques | Szatkiewicz, Jin P | Taico, Chrysecolla | Zerwas, Stephanie | Trace, Sara E | Davis, Oliver SP | Helder, Sietske | Bühren, Katharina | Burghardt, Roland | de Zwaan, Martina | Egberts, Karin | Ehrlich, Stefan | Herpertz-Dahlmann, Beate | Herzog, Wolfgang | Imgart, Hartmut | Scherag, André | Scherag, Susann | Zipfel, Stephan | Boni, Claudette | Ramoz, Nicolas | Versini, Audrey | Brandys, Marek K | Danner, Unna N | de Kovel, Carolien | Hendriks, Judith | Koeleman, Bobby PC | Ophoff, Roel A | Strengman, Eric | van Elburg, Annemarie A | Bruson, Alice | Clementi, Maurizio | Degortes, Daniela | Forzan, Monica | Tenconi, Elena | Docampo, Elisa | Escaramís, Geòrgia | Jiménez-Murcia, Susana | Lissowska, Jolanta | Rajewski, Andrzej | Szeszenia-Dabrowska, Neonila | Slopien, Agnieszka | Hauser, Joanna | Karhunen, Leila | Meulenbelt, Ingrid | Slagboom, P Eline | Tortorella, Alfonso | Maj, Mario | Dedoussis, George | Dikeos, Dimitris | Gonidakis, Fragiskos | Tziouvas, Konstantinos | Tsitsika, Artemis | Papezova, Hana | Slachtova, Lenka | Martaskova, Debora | Kennedy, James L. | Levitan, Robert D. | Yilmaz, Zeynep | Huemer, Julia | Koubek, Doris | Merl, Elisabeth | Wagner, Gudrun | Lichtenstein, Paul | Breen, Gerome | Cohen-Woods, Sarah | Farmer, Anne | McGuffin, Peter | Cichon, Sven | Giegling, Ina | Herms, Stefan | Rujescu, Dan | Schreiber, Stefan | Wichmann, H-Erich | Dina, Christian | Sladek, Rob | Gambaro, Giovanni | Soranzo, Nicole | Julia, Antonio | Marsal, Sara | Rabionet, Raquel | Gaborieau, Valerie | Dick, Danielle M | Palotie, Aarno | Ripatti, Samuli | Widén, Elisabeth | Andreassen, Ole A | Espeseth, Thomas | Lundervold, Astri | Reinvang, Ivar | Steen, Vidar M | Le Hellard, Stephanie | Mattingsdal, Morten | Ntalla, Ioanna | Bencko, Vladimir | Foretova, Lenka | Janout, Vladimir | Navratilova, Marie | Gallinger, Steven | Pinto, Dalila | Scherer, Stephen | Aschauer, Harald | Carlberg, Laura | Schosser, Alexandra | Alfredsson, Lars | Ding, Bo | Klareskog, Lars | Padyukov, Leonid | Finan, Chris | Kalsi, Gursharan | Roberts, Marion | Logan, Darren W | Peltonen, Leena | Ritchie, Graham RS | Barrett, Jeffrey C | Estivill, Xavier | Hinney, Anke | Sullivan, Patrick F | Collier, David A | Zeggini, Eleftheria | Bulik, Cynthia M
Molecular psychiatry  2010;16(9):10.1038/mp.2010.107.
Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2,907 cases with AN from 14 countries (15 sites) and 14,860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery datasets. Seventy-six (72 independent) SNPs were taken forward for in silico (two datasets) or de novo (13 datasets) replication genotyping in 2,677 independent AN cases and 8,629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication datasets comprised 5,551 AN cases and 21,080 controls. AN subtype analyses (1,606 AN restricting; 1,445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01×10−7) in SOX2OT and rs17030795 (P=5.84×10−6) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76×10−6) between CUL3 and FAM124B and rs1886797 (P=8.05×10−6) near SPATA13. Comparing discovery to replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P= 4×10−6), strongly suggesting that true findings exist but that our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.
doi:10.1038/mp.2010.107
PMCID: PMC3859494  PMID: 21079607
anorexia nervosa; eating disorders; GWAS; genome-wide association study; body mass index; metabolic
8.  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 post-pubertal female twins (ages 12–22; M=17.61) from the Michigan State University Twin Registry. Thin-ideal internalization was assessed using the Sociocultural Attitudes toward Appearance Questionniare-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.
doi:10.1002/eat.22056
PMCID: PMC3523121  PMID: 23034902
Thin-ideal; internalization; body image; disordered eating; twin study; heritability; Tripartite Model
9.  Parental Divorce and Disordered Eating: An Investigation of a Gene-Environment Interaction 
Objective
We investigated gene-environment interactions (G×E) for associations between parental divorce and disordered eating (DE).
Method
Participants were 1,810 female twins from the Michigan State University Twin Registry and the Minnesota Twin Family Study. The Minnesota Eating Behaviors Survey was used to assess DE. We tested for G×E by comparing the heritability of DE in twins from divorced versus intact families. It was hypothesized that divorce would moderate the heritability of DE, in that heritability would be higher in twins from divorced than twins from intact families.
Results
As expected, the heritability of body dissatisfaction was significantly higher in twins from divorced than intact families. However, genetic influences were equal in twins from divorced and intact families for all other forms of DE.
Discussion
Although divorce did not moderate heritability of most DE symptoms, future research should replicate G×Es for body dissatisfaction and identify factors underlying this unique relationship.
doi:10.1002/eat.20866
PMCID: PMC3058816  PMID: 21312202
Disordered Eating; Parental Divorce; Gene-Environment Interaction; Eating Disorders; Twins
10.  Dietary Restraint Moderates Genetic Risk for Binge Eating 
Journal of abnormal psychology  2011;120(1):119-128.
Dietary restraint is a prospective risk factor for the development of binge eating and bulimia nervosa. Although many women engage in dietary restraint, relatively few develop binge eating. Dietary restraint may only increase susceptibility for binge eating in individuals who are at genetic risk. Specifically, dietary restraint may be a behavioral “exposure” factor that activates genetic predispositions for binge eating. We investigated this possibility in 1,678 young adolescent and adult same-sex female twins from the Minnesota Twin Family Study and the Michigan State University Twin Registry. Twin moderation models were used to examine whether levels of dietary restraint moderate genetic and environmental influences on binge eating. Results indicated that genetic and non-shared environmental factors for binge eating increased at higher levels of dietary restraint. Importantly, these effects were present after controlling for age, body mass index, and genetic and environmental overlap among dietary restraint and binge eating. Results suggest that dietary restraint may be most important for individuals at genetic risk for binge eating, and the combination of these factors could enhance individual differences in risk for binge eating.
doi:10.1037/a0020895
PMCID: PMC3057961  PMID: 21171725
binge eating; dietary restraint; gene-environment interactions; twins
11.  Etiological Distinctions between Aggressive and Non-aggressive Antisocial Behavior: Results from a Nuclear Twin Family Model 
Journal of abnormal child psychology  2012;40(7):1059-1071.
A recent meta-analysis of 103 studies Burt (Clinical Psychology Review, 29:163–178, 2009a) highlighted the presence of etiological distinctions between aggressive (AGG) and non-aggressive rule-breaking (RB) dimensions of antisocial behavior, such that AGG was more heritable than was RB, whereas RB was more influenced by the shared environment. Unfortunately, behavioral genetic research on antisocial behavior to date (and thus, the research upon which the meta-analysis was based) has relied almost exclusively on the classical twin model. This reliance is problematic, as the strict assumptions that undergird this model (e.g., shared environmental and dominant genetic influences are not present simultaneously; there is no assortative mating) can have significant consequences on heritability estimates when they are violated. The nuclear twin family model, by contrast, allows researchers to relax and statistically evaluate many of the assumptions of the classical twin design by incorporating parental self-report data along with the more standard twin data. The goal of the current study was thus to evaluate whether prior findings of etiological distinctions between AGG and RB persisted when using the nuclear twin family model. We examined a sample of 312 child twin families from the Michigan State University Twin Registry. Results strongly supported prior findings of etiological distinctions between AGG and RB, such that broad genetic influences were observed to be particularly important to AGG whereas shared environmental influences contributed only to RB. Nevertheless, the current findings also implied that additive genetic influences on antisocial behavior may be overestimated when using the classical twin design.
doi:10.1007/s10802-012-9632-9
PMCID: PMC3406250  PMID: 22466619
Antisocial behavior; Aggression; Rule-breaking; Nuclear twin family model
12.  Preliminary Evidence that Estradiol Moderates Genetic Influences on Disordered Eating Attitudes and Behaviors During Puberty 
Psychological medicine  2010;40(10):1745-1753.
Background
Puberty moderates genetic influences on disordered eating attitudes and behaviors, with little genetic influence before puberty but large (≥ 50%) genetic effects during and after puberty. To date, however, nothing is known about the mechanisms that underlie these effects. Estradiol is a particularly promising candidate, as estrogens become elevated at puberty and regulate gene transcription within neurotransmitter systems important for eating-related phenotypes. The aim of this pilot study was to examine whether estradiol levels moderate genetic influences on disordered eating during puberty.
Methods
Participants included 198 female twins (ages 10-15 years) from the Michigan State University Twin Registry. Disordered eating attitudes and behaviors were assessed with the total score, weight preoccupation, body dissatisfaction, and binge eating/compensatory behavior subscales of the Minnesota Eating Behavior Survey. Afternoon saliva samples were assayed for estradiol levels. Moderation of genetic effects was examined by comparing twin correlations in low versus high estradiol groups.
Results
In the low estradiol group, monozygotic (MZ) and dizygotic (DZ) twin correlations for all MEBS scales were similar, suggesting little genetic influence. In the high estradiol group, the MZ twin correlation was more than double the DZ twin correlation, indicating the presence of genetic effects. Findings could not be accounted for by age, body mass index, or the physical changes of puberty.
Conclusions
Estradiol may be one important moderator of genetic effects on disordered eating during puberty. Larger twin studies are needed to replicate this pilot work and quantify the extent of genetic moderation.
doi:10.1017/S0033291709992236
PMCID: PMC2928391  PMID: 20059800
13.  Additional Evidence against Shared Environmental Contributions to Attention-Deficit/Hyperactivity Problems 
Behavior genetics  2012;42(5):711-721.
A recent meta-analysis (Burt, 2009) indicated that shared environmental influences (C) do not contribute to Attention-Deficit/Hyperactivity Disorder (ADHD). Unfortunately, the meta-analysis relied almost exclusively on classical twin studies. Although useful in many ways, some of the assumptions of the classical twin model (e.g., dominant genetic and shared environmental influences do not simultaneously influence the phenotype) can artifactually decrease estimates of C. There is thus a need to confirm that dominant genetic influences are not suppressing estimates of C on ADHD. The current study sought to do just this via the use of a nuclear twin family model, which allows researchers to simultaneously model and estimate dominant genetic and shared environmental influences. We examined two independent samples of child twins: 312 pairs from the Michigan State University Twin Registry (MSUTR) and 854 pairs from the PrEschool Twin Study in Sweden (PETSS). Shared environmental influences were found to be statistically indistinguishable from zero and accounted for less than 5% of the variance. We conclude that the presence of dominant genetic influences does not account for the absence of C on ADHD.
doi:10.1007/s10519-012-9545-y
PMCID: PMC3440545  PMID: 22566176
ADHD; nuclear twin family model; shared environment; genetic influences
14.  A Longitudinal Investigation of the Relationship between Disordered Eating Attitudes and Behaviors and Parent-Child Conflict: A Monozygotic Twin Differences Design 
Journal of abnormal psychology  2010;119(2):293-299.
Few studies have examined nonshared environmental risk factors for disordered eating, and none have done so using a longitudinal design. The current project employed 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, followed every three years from ages 11 to 17. 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 and differences in parent-child conflict at age 17 was 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.
doi:10.1037/a0019028
PMCID: PMC2941761  PMID: 20455602
15.  The Possible Influence of Impulsivity and Dietary Restraint on Associations between Serotonin Genes and Binge Eating 
Journal of psychiatric research  2009;43(16):1278-1286.
Although serotonin (5-HT) genes are thought to be involved in the etiology of bulimia nervosa and binge eating, findings from molecular genetic studies are inconclusive. This may be due to limitations of past research, such as a failure to consider the influence of quantitative traits and gene-environment interactions. The current study investigated these issues by examining whether quantitative traits (i.e., impulsivity) and environmental exposure factors (i.e., dietary restraint) moderate 5-HT gene/binge eating associations in a sample of young women (N = 344). Binge eating was assessed using the Minnesota Eating Behaviors Survey and the Dutch Eating Behavior Questionnaire (DEBQ). Impulsivity was assessed with the Barratt Impulsiveness Scale-Version 11. Dietary restraint was measured with a factor score derived from common restraint scales. Saliva samples were genotyped for the 5-HT2a receptor T102C polymorphism and 5-HT transporter promoter polymorphism. As expected, impulsivity and dietary restraint were associated with binge eating. Although the T allele of the 5-HT2a receptor gene and the s allele of the 5-HTT gene were associated with higher levels of impulsivity, there were no main effects of 5-HT genotypes on any binge eating measure, and interactions between genotypes, impulsivity, and dietary restraint were non-significant. In conclusion, we found no evidence to suggest that dietary restraint or impulsivity moderate associations between binge eating and these 5-HT genes. Future research should continue to explore interaction effects by examining larger samples, assessing dietary intake directly, and investigating other genes, traits, and environmental factors that may be related to binge eating and bulimia nervosa.
doi:10.1016/j.jpsychires.2009.05.002
PMCID: PMC2870529  PMID: 19493540
binge eating; serotonin; impulsivity; dietary restraint; gene-environment interactions
16.  Puberty and the Genetic Diathesis of Disordered Eating Attitudes and Behaviors 
Journal of abnormal psychology  2009;118(4):788-796.
Twin studies from the Minnesota Twin Family Study (MTFS) suggest negligible genetic effects on eating pathology before puberty, but increased genetic effects during puberty. However, an independent study found no pubertal differences in genetic and environmental effects (Rowe et al., 2002). Discrepant results may be due to methodological differences. The MTFS studies divided twins at mid-puberty, while Rowe et al. (2002) divided twins based on menarche alone. We aimed to reconcile discrepant findings by examining differences in etiologic effects for disordered eating attitudes and behaviors (i.e., levels of weight preoccupation, body dissatisfaction, binge eating, compensatory behaviors) using both classification methods in a new sample of 656 female twins. Using the MTFS method, we observed nominal genetic effects in pre-pubertal twins, but significant genetic effects in pubertal and young adult twins. Conversely, genetic effects were moderate and equal in all groups using the Rowe et al. (2002) method. Findings highlight the potentially important role of puberty in the genetic diathesis of disordered eating attitudes and behaviors and the need to use early indicators of pubertal status in studies of developmental effects.
doi:10.1037/a0017207
PMCID: PMC2782672  PMID: 19899848
eating disorders; anorexia nervosa; bulimia nervosa; twins; genetic
17.  Prenatal Hormone Exposure and Risk for Eating Disorders: A Comparison of Opposite-Sex and Same-Sex Twins 
Archives of general psychiatry  2008;65(3):329-336.
Context
Although the sex difference in eating disorder prevalence has typically been attributed to psychosocial factors, biological factors may also play a role. Prenatal testosterone exposure is a promising candidate, as it masculinizes behavior in animals and humans via its permanent effects on the central nervous system.
Objective
We examined whether in utero testosterone exposure has masculinizing effects on disordered eating (DE) by comparing opposite-sex (OS) and same-sex (SS) twins. Twin type (SS versus OS) is considered a proxy measure of prenatal hormone exposure, as females from OS pairs are exposed to more testosterone in utero than females from SS pairs. A linear trend in mean levels of DE was predicted based on expected prenatal testosterone exposure, with SS female twins exhibiting the highest levels of DE followed by OS female twins, OS male twins, and SS male twins.
Participants
Participants included 304 SS female twins, 59 OS female twins, 54 OS male twins, and 165 SS male twins from the Michigan State University Twin Registry (MSUTR).
Main Outcome Measures
Overall levels of disordered eating were assessed with the Minnesota Eating Behavior Survey.
Results
Confirming hypotheses, DE exhibited significant linear trends with SS female twins exhibiting the highest levels of DE followed by OS female twins, OS male twins, and SS male twins. This linear trend could not be accounted for by levels of anxiety or socialization effects. Indeed, OS female twins exhibited lower levels of DE compared to an independent sample of undergraduate women (N = 69) who were raised with one or more brothers.
Conclusions
The masculinization of DE in OS female twins is unlikely to be due to socialization effects alone. Biological factors, such as the masculinization of the central nervous system by prenatal testosterone, may also contribute to sex differences in DE prevalence.
doi:10.1001/archgenpsychiatry.2007.47
PMCID: PMC2883912  PMID: 18316679
eating disorder; disordered eating; sex difference; organizational effects; testosterone; twins
18.  Molecular Genetic Studies of Eating Disorders 
We review association studies that have examined the genetic basis of eating disorders. Overall, findings suggest that serotonin, brain-derived neurotrophic factor, and estrogen genes may be important for the development of the disorders. These neuronal systems influence behavioral and personality characteristics (e.g., anxiety, food intake) that are disrupted in eating disorders. Future studies would benefit from larger sample sizes and inclusion of behavioral and personality covariates in analyses. Consideration of the mechanisms of genetic effects and interactions between genes and environment is also needed to extend conceptualizations of the genetic basis of these disorders.
doi:10.1111/j.1467-8721.2007.00471.x
PMCID: PMC2882694  PMID: 20539827
anorexia nervosa; bulimia nervosa; genetic; gene
19.  The Effects of Puberty on Genetic Risk for Disordered Eating: Evidence for a Sex Difference 
Psychological medicine  2011;42(3):627-637.
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 1,006 male and female twins from the Michigan State University Twin Registry.
Methods
Disordered eating was assessed with the Minnesota Eating Behaviors 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
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.
doi:10.1017/S0033291711001541
PMCID: PMC3697115  PMID: 21854699
eating disorders; males; genetic; twins; puberty; sex differences
20.  Negative Affect as a Mediator of the Relationship between Weight-Based Teasing and Binge Eating in Adolescent Girls 
Eating behaviors  2008;9(4):493-496.
Previous research has established a link between weight-based teasing and binge eating, though the precise mechanisms that drive this relationship remain unknown. This study examined negative affect as a mediator of the relationship between weight-based teasing and binge eating. Participants included 265 adolescent female twins (aged 10–15 years). Self-report measures assessed binge eating, weight-based teasing, and negative affect. Mediation was tested within hierarchical linear models to control for the non-independence of the twin data. Significant positive associations were observed between binge eating, teasing, and negative affect. In the regression analyses, negative affect partially mediated associations between weight-based teasing and binge eating. Results suggest that increases in negative affect are one way in which weight-based teasing leads to binge eating in girls. Future studies should examine additional mediators and assess possible clinical applications of these findings.
doi:10.1016/j.eatbeh.2008.04.001
PMCID: PMC2600662  PMID: 18928913
Negative affect; binge eating; eating disorders; teasing; weight-based teasing; disordered eating
21.  The Significance of Repetitive Hair-Pulling Behaviors in Eating Disorders 
Journal of clinical psychology  2011;67(4):391-403.
We studied the relation between intrusive and repetitive hair-pulling, the defining feature of trichotillomania, and compulsive and impulsive features in 1453 individuals with anorexia nervosa and bulimia nervosa. We conducted a series of regression models examining the relative influence of compulsive features associated with obsessive compulsive disorder; compulsive features associated with eating disorders; trait features related to harm avoidance, perfectionism and novelty seeking; and self harm. A final model with a reduced sample (n=928) examined the additional contribution of impulsive attributes. One out of 20 individuals endorsed hair-pulling. Evidence of a positive association with endorsement of compulsive behavior of the obsessive compulsive spectrum emerged. Hair-pulling may be more consonant with ritualistic compulsions than impulsive urges in those with eating disorders.
doi:10.1002/jclp.20770
PMCID: PMC3664303  PMID: 21365638
eating disorders; trichotillomania; hair-pulling; anorexia nervosa; bulimia nervosa; impulsivity; compulsivity
22.  Youth Appraisals of Inter-parental Conflict and Genetic and Environmental Contributions to Attention-Deficit Hyperactivity Disorder: Examination of G×E Effects in a Twin Sample 
Identification of gene × environment interactions (GxE) for attention-deficit hyperactivity disorder (ADHD) is a crucial component to understanding the mechanisms underpinning the disorder, as prior work indicates large genetic influences and numerous environmental risk factors. Building on prior research, children's appraisals of self-blame were examined as a psychosocial moderator of latent etiological influences on ADHD via biometric twin models, which provide an omnibus test of GxE while managing the potential confound of gene-environment correlation. Participants were 246 twin pairs (total n=492) ages 6–16 years. ADHD behaviors were assessed via mother report on the Child Behavior Checklist. To assess level of self-blame, each twin completed the Children's Perception of Inter-parental Conflict scale. Two biometric GxE models were fit to the data. The first model revealed a significant decrease in genetic effects and a significant increase in unique environmental influences on ADHD with increasing levels of self-blame. These results generally persisted even after controlling for confounding effects due to gene-environment correlation in the second model. Results suggest that appraisals of self-blame in relation to inter-parental conflict may act as a key moderator of etiological contributions to ADHD.
doi:10.1007/s10802-011-9583-6
PMCID: PMC3334526  PMID: 22006350
Gene × environment interaction; Inter-parental conflict; Attention-deficit hyperactivity disorder
23.  Understanding the Association of Impulsivity, Obsessions, and Compulsions with Binge Eating and Purging Behaviors in Anorexia Nervosa 
Objective
To further refine our understanding of impulsivity, obsessions, and compulsions in anorexia nervosa (AN) by isolating which behaviors—binge eating, purging, or both—are associated with these features.
Methods
We conducted regression analyses with binge eating, purging, and the interaction of binge eating with purging as individual predictors of scores for impulsivity, obsessions, and compulsions in two samples of women with AN (n = 1373).
Results
Purging, but not binge eating, was associated with higher scores of impulsivity, obsessions and compulsions. Purging was also associated with worst eating rituals and with worst eating preoccupations.
Conclusion
Our results suggest that purging, compared with binge eating, may be a stronger correlate of impulsivity, obsessions, and compulsions in AN.
doi:10.1002/erv.2161
PMCID: PMC3443865  PMID: 22351620
anorexia nervosa; impulsivity; compulsivity; binge eating; purging
24.  Differential Associations between Ovarian Hormones and Disordered Eating Symptoms across the Menstrual Cycle in Women 
Objective
We examined changes in drive for thinness, body dissatisfaction, and dietary restraint across the menstrual cycle and associations between these symptoms and ovarian hormones in two independent samples of women (N = 10 and 8 women, respectively) drawn from the community.
Method
Daily self-report measures of disordered eating and negative affect were completed for 35–65 days. Daily saliva samples were assayed for estradiol and progesterone in Study 2 only.
Results
Levels of body dissatisfaction and drive for thinness were highest during the mid-luteal/pre-menstrual phases in both studies and were negatively associated with estradiol, and positively associated with progesterone. By contrast, dietary restraint showed less variation across the menstrual cycle and weaker associations with ovarian hormones.
Discussion
Differential associations between ovarian hormones and specific disordered eating symptoms point to distinct etiological processes within the broader construct of disordered eating.
doi:10.1002/eat.20941
PMCID: PMC3170673  PMID: 21656540
estradiol; progesterone; ovarian hormones; menstrual cycle; eating disorders; disordered eating; drive for thinness; body dissatisfaction; dietary restraint
25.  Retrospective Maternal Report of Early Eating Behaviors in Anorexia Nervosa 
European Eating Disorders Review  2011;20(2):111-115.
This exploratory study assessed whether maternal recall of childhood feeding and eating practices differed across anorexia nervosa (AN) subtypes. Participants were 325 women from the Genetics of Anorexia Nervosa study whose mothers completed a childhood feeding and eating questionnaire. Multinomial logistic regression analyses were used to predict AN subtype from measures related to childhood eating: (a) infant feeding (breastfed, feeding schedule, age of solid food introduction), (b) childhood picky eating (picky eating before age one and between ages one and five), and (c) infant gastrointestinal problems (vomiting and colic). Results revealed no significant differences in retrospective maternal report of childhood feeding and eating practices among AN subtypes.
doi:10.1002/erv.1153
PMCID: PMC3391535  PMID: 21830261
Anorexia Nervosa; Anorexia Nervosa Subtype; Feeding; Maternal Report; Infancy

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