This comparison of personality dimensions among eating and weight disordered groups suggests that individuals with BN are prone to experience more negative emotions and less contentment, as well as be more reactive to stress, than individuals with BED, obese individuals who do not binge eat, and normal-weight individuals without eating disorders. Elevated scores of stress reactivity in BN were independent of depression scores, suggesting that these individuals are generally more nervous, upset, and troubled by guilt than the other groups [29
]. These findings are consistent with previous studies that have observed higher stress reactivity and neuroticism scores in BN compared to non-eating disorder samples using the MPQ and other personality assessment instruments [37
The results of this investigation also indicate that individuals with BED reported higher harm avoidance scores than the non-dieting, normal weight control sample, suggesting that individuals with BED may be more averse to danger and adventure. This difference was independent of current depression and is consistent with previous findings of high harm avoidance in other eating disorder diagnostic groups [47
]. The reason for elevated harm avoidance is unclear but may be related to attempts to avoid painful situations, which has been hypothesized to explain high harm avoidance scores among individuals with borderline personality disorder [20
]. The absence of group differences other than harm avoidance between individuals with BED and obese non-binge eaters is consistent with previous findings [49
] and suggests that those with BED may be similar in many respects to those of comparable weight who do not binge eat.
In this study, individuals with BN reported lower positive emotionality, lower well being, and higher negative emotionality compared to NWC participants (as well as lower well being scores compared to the OB group), and individuals with BED reported lower well being scores compared to the NWC group. However, these differences were not independent of depression in the subsequent covariate analyses. The extent to which measures of negative emotionality and positive emotionality traits are influenced by self-reported depressive symptoms is unclear. Although it is possible that the apparent differences in negative emotionality, positive emotionality, and well being are simply artifacts of depression, it is likely that measures of depression and personality used in this study overlap in their measurement of both “state” and “trait” aspects of negative affect. The extent to which these group differences are best understood as personality traits, mood disorders, or both is unclear; however, negative emotionality, positive emotionality, and well being clearly should be targeted in the treatment of BN and BED and should be continue to be examined for their role in the etiology and maintenance of these disorders.
Several limitations should be considered in interpreting the results of this study. First, the BN and BED samples include participants in two different treatment trials, meaning that the two eating disorder groups were treatment seeking. Berkson’s bias [50
] indicates that individuals with psychopathology who seek treatment may have greater co-occurring psychopathology than those who do not seek treatment. Thus, the participants with BN and BED in this study may not be representative of individuals in the community with these eating disorders who do not seek treatment. In addition, data from all four groups were obtained at different time points, which may have exaggerated between-group differences. A significant consideration in the current study is the difficulty in reliably assessing personality in individuals with eating disorders due to the effect of these symptoms on personality measures [6
]. An additional concern is the extent to which these personality “traits” are stable over time. For example, elevated harm avoidance scores in patients with borderline personality disorder have been found to be reduced over the course of treatment [20
]; for this reason, future research should investigate the stability of personality dimensions among different eating and weight disorder subgroups over time. In addition, future studies should examine the impact of controlling for anxiety as well as depression on personality measures in eating disorders. Finally, because this investigation is correlational and not longitudinal, no direction of causality can be inferred: whether these personality dimensions are etiological or maintenance factors, byproducts of the eating disorder or of “maladjustment” [51
], or some combination is unclear and needs further study using repeated measure designs.
In summary, stress reactivity appears to be especially important in understanding and treating BN and harm avoidance is crucial to understanding and treating BED. In addition, high negative emotionality, low positive emotionality, and low well being are notable features of BN and BED and although the extent to which these variables are independent of depression is unclear, they clearly necessitate focus in treatment. Treatments for eating disorders that focus on mood tolerance and coping skills may be particularly effective, including dialectical behavior therapy [52
] and the revised version of cognitive-behavior therapy [55
], as well as Integrative Cognitive-Affective Therapy [56
], a newly developed treatment that focuses on self-directed style, interpersonal patterns, and emotion. The potential efficacy of these types of interventions on personality dimensions and treatment outcome requires future study among all types of eating disorder subgroups.