Is the relationship between binge eating episodes and personality attributable to genetic factors

Anorexia nervosa and bulimia nervosa affect approximately 0.9% and 1.5% of women, respectively (Hudson, Hiripi, Pope, Jr., & Kessler, 2007). Despite these seemingly modest rates, disordered eating is a serious mental health problem, especially for women in their teens and early twenties, contributing to significant morbidity and mortality (Whiteford et al., 2013). While clinical diagnoses are relatively rare, the frequency of specific disordered eating symptoms, such as episodes of binge eating (eating a large amount of food in a discrete period of time, accompanied by a sense of loss of control) are reported to be more prevalent. For example, a population based study conducted by Hudson and colleagues (2007) found the lifetime prevalence of bulimia nervosa to be around 1.5% in women, but the prevalence of binge eating behavior (i.e. recurrent episodes of binge eating accompanied by lack of control during episodes, occurring two times a week for three months or longer) alone to be 4.5% (Hudson et al., 2007). Prior research has suggested that personality traits may play a distinct role in the development of eating pathology (see Cassin & von Ranson, 2005 for a review). High neuroticism scores have been consistently correlated with eating disorder diagnoses. Results for other indices of personality have been equivocal. For instance, mixed evidence suggests that lower conscientiousness and agreeableness and greater openness to experience are associated with eating disorders, although the association with openness may be mediated by low neuroticism and agreeableness scores. Extraversion, on the other hand, appears to have weak to nonexistent associations with disordered eating. Increased impulsivity and novelty-seeking has also been noted among individuals with bulimia nervosa, the binge/purge subtype of anorexia nervosa, and those who binge eat compared with control individuals. Other aspects of temperament, such as harm avoidance are also elevated across all subtypes of eating disorders. Taken together, these studies suggest that personality traits may be contributors to the etiology of disordered eating. Aspects of disordered eating (e.g. binge eating episodes) and personality traits are moderately heritable. Previous research has indicated that disordered eating characteristics are influenced by additive genetic effects and individual-specific environmental effects, with shared environment playing a negligible role overall. Specifically, for binge eating, heritability estimates range from 17%–82% (Bulik et al., 1998; Bulik, Sullivan, & Kendler, 2003; Munn et al., 2010; Munn-Chernoff et al., 2013; Reichborn-Kjennerud et al., 2003; Reichborn-Kjennerud, Bulik, Tambs, & Harris, 2004; Wade, Treloar, & Martin, 2008). Likewise, additive genetic and individual-specific environmental factors account for the majority of the variance in personality traits (Jang, Livesley, & Vernon, 1996; Viken, Rose, Kaprio, & Koskenvuo, 1994) with heritabilities ranging from 40–55% (Jang et al., 1996; Bezdjian, Baker, & Tuvblad, 2011; Luciano, Wainwright, Wright, & Martin, 2006; Finkel & McGue, 1997). Similar to binge eating, there is little evidence for shared environmental factors; however, some studies have supported the role of non-additive genetic influences on personality, particularly neuroticism, as assessed via the Eysenck Personality Questionnaire (Keller, Coventry, Heath, & Martin, 2005; Eaves, Heath, Neale, Hewitt, & Martin, 1998; Lake, Eaves, Maes, Heath, & Martin, 2000) but not when measured using other scales, such as the NEO Inventories (Jang et al., 1996; Jang, McCrae, Angleitner, Riemann, & Livesley, 1998). Despite this evidence for phenotypic correlations between aspects of disordered eating, particularly binge eating, and personality traits, and their individual, heritable underpinnings, only three studies have investigated the overlap of genetic and environmental factors on disordered eating and personality. Wade and colleagues (Wade et al., 2000) examined the overlapping origins of eating pathology (score across 16 items related to disordered eating), personality traits such as neuroticism and self-esteem, and factors pertaining to perceptions of parental bonding in middle-aged women. From a single independent pathway model, they noted that individual-specific environmental factors accounted for a large proportion of the variance in and covariance between a majority of the variables with little evidence for shared genetic influences. A second study (Klump, McGue, & Iacono, 2002) of adolescent girls reported significant correlations between negative emotionality (tendency to experience negative mood states, such as anxiety; Tellegen, 1982), positive emotionality (tendency to be social and engage in positive mood states) and constraint and aspects of disordered eating such as body dissatisfaction, weight preoccupation, compensatory behaviors and binge eating. Unlike the prior study (Wade et al., 2000), Klump and colleagues (2002) concluded that additive genetic and individual-specific environmental factors best explained the overlap between personality traits and aspects of disordered eating. Finally, a recent study (Racine et al., 2013) examined associations among negative urgency (or the tendency to act rashly or impulsively in response to negative affect), negative affect, binge eating, and emotional eating in late adolescent girls and young adult women. Similar to Klump and colleagues (2002), genetic and individual-specific environmental factors contributed most to the overlap of these phenotypes, with the largest proportion of the correlation explained by genetic factors. Thus, the evidence surrounding the role of genetic contributions to the correlation between aspects of disordered eating and personality remain mixed and largely restricted to personality indices of negative mood states. In an effort to extend this literature, the aim of the current study was to examine the association between personality traits (neuroticism, extraversion, conscientiousness, agreeableness, openness to experience and control/impulsivity) and binge eating episode, the most widely studied aspect of disordered eating and now, the basis for the new DSM-5 binge eating disorder (American Psychiatric Association, 2013). As noted above, prior studies have largely focused on neuroticism alone or broader domains of negative mood states and we are not aware of any study that has explored the role of genetic factors in the relationship between additional personality measures (e.g., conscientiousness) and binge eating episodes. For those personality traits that were significantly associated with binge eating, we then examined the extent to which genetic and environmental factors contributed to this correlation.