Abstract

Both environmental and genetic factors play an important role in the etiology of Bulimia Nervosa (BN). A number of critical environmental factors in the development of BN are not shared by family members; specifically, perceived nonshared environmental factors (e.g., differential parent-child relationships) may be more influential in the development of psychopathology and personality than are shared factors (e.g., general family dynamics). Therefore, the present study was designed to identify the differential environments experienced by bulimics and their sisters by assessing nonshared environmental influences associated with BN. In particular, sibling differential experiences and the influence of personality traits on the risk of developing BN were addressed. Forty bulimics and their non-eating disordered sisters were assessed for (a) eating pathology, (b) perceived nonshared environmental factors in three areas (i.e., differential parent-child relationship, quality of the sibling relationship, developmental experiences), (c) personality traits (i.e., implusivity, affective instability, narcissism), and (d) psychopathology. In general, bulimics exhibited higher levels of eating disturbances and psychopathology than sisters. Furthermore, compared to their sisters, bulimics reported being more insecurely attached to their fathers, higher levels of past shape and weight-related teasing experiences, and greater impulsivity, affective instability, and narcissism. However, perceptions of differential parental affection, quality of the sibling relationship, childhood sexual and physical abuse, as well as perceptions of parental dieting behaviors were identified as perceived shared environmental features. In terms of an etiological understanding of BN, the results of the logistic regression analyses revealed that both specific nonshared risk factors (i.e., perceptions of shape and weight-related teasing) and nonspecific risk factors (i.e., insecure paternal attachment, narcissism) significantly distinguished bulimics from their sisters, after accounting for depression and anxiety. Therefore, these perceived nonshared environmental influences may constitute vulnerability factors that predispose individuals to the development of BN. Implications of these findings are discussed in the light of existing models of risk factors involved in the etiology of BN.