Purpose Although personality has been widely researched in patients with anorexia nervosa (AN) and bulimia nervosa (BN), the nature of this relationship has not yet been clearly articulated. The pathoplasty model theorizes that personality might shape symptomatic presentation and thus affect therapeutic outcomes, but more research is needed. The present study aimed at investigating the predictive value of a broad spectrum of personality traits in determining AN and BN treatment outcomes, considering both the statistical and clinical significance of the therapeutic change. Methods Eighty-four female patients with AN and BN treated in a residential program were evaluated at treatment onset using the Shedler-Westen Assessment Procedure-200—a clinician-rated measure of personality disorders and healthy personality functioning. At both intake and discharge, patients completed the Eating Disorder Inventory-3 to assess eating symptoms and the Outcome Questionnaire-45.2 to evaluate overall impairment. Results Considering overall ED symptomatic change, multiple regression analyses showed that, even when controlling for baseline symptoms and DSM-5 categories, schizoid (B = 0.41, p ≤ 0.01), avoidant (B = 0.31, p ≤ 0.05), and paranoid (B = 0.25, p ≤ 0.05) personality features predicted worse therapeutic outcomes. Similar results were found when applying the clinical significance approach, with the emotionally dysregulated factor as an additional negative predictor of significant/reliable change (B =  − 0.09; p < 0.01). Healthy personality functioning predicted better therapeutic outcomes (B =  − 0.34, p ≤ 0.001). Conclusions Pathoplastic models and personality-based research in this clinical population have the potential to inform effective treatment strategies by targeting relevant individual factors. Level of evidence Level III, longitudinal cohort study.

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) categorical classification of eating disorders (ED) has faced substantial criticism due to its limited ability to assess patients’ individual characteristics and thereby evaluate the most appropriate treatment options. The current study aimed at exploring the validity of the Psychodynamic Diagnostic Manual (PDM-2) diagnostic approach to ED by evaluating the treatment outcomes of a psychodynamic-oriented residential intervention. At the start of treatment, a national sample of 73 female ED patients was evaluated using both the Structured Clinical Interview for DSM-5 (SCID-5-CV) and the Psychodiagnostic Chart-2 (PDC-2)—a PDM-2 derived clinician-rated tool. Participants were also asked to complete a self-report questionnaire on ED symptomatic impairment at treatment intake and discharge. Results showed the overall effectiveness of the psychodynamic residential treatment in terms of therapeutic change in ED-specific psychopathology. Even when controlling for baseline ED symptoms, higher levels of personality organization and a lower severity of personality pathology were found to predict lower levels of ED-specific psychopathology at discharge. Similarly, higher levels of overall mental functioning, as well as higher mentalizing capacity, identity integration, and self-coherence, were found to relate to better therapeutic outcomes. DSM-5 categories did not impact either pre–post change or symptomatic change at treatment termination. Results suggest that the PDM-2 diagnostic approach could promote a better conceptualization of potential maintenance factors to target in psychotherapy, generating a comprehensive perspective with maximal clinical utility.

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Features of personality disorders (PDs) have been found to explain meaningful variance in the onset, maintenance, and symptomatic presentation of eating disorders (EDs), and a co-occurent personality pathology is commonly associated with poorer response to ED treatment. The “pathoplasty model” of the relationship between personality and EDs implies that, once both conditions are established, they are likely to interact in ways that modify therapy outcome; however, to date, no studies have explored overall personality functioning, and especially PD clusters, as a mediator of treatment outcome. The present study aimed at conjointly exploring the associations between personality functioning and PDs, respectively, with pre-treatment ED symptomatic impairment and therapy outcome; and the mediating role of personality variables. At treatment onset, a sample of 107 women with ED problems were evaluated using both the Structured Clinical Interview for DSM-5 (SCID-5-CV) and the Shedler-Westen Assessment Procedure-200 (SWAP-200)—a clinician-rated procedure to dimensionally assess personality. Participants were also asked to complete self-report questionnaires on overall ED symptomatology, symptoms of binge eating and purging behaviors, and therapy outcome. The findings showed that, over and above the categorical ED diagnosis, the SWAP-200 healthy personality functioning score mediated the relationship between baseline ED symptom severity and therapy outcome, as well as the association between baseline bulimic symptoms and treatment outcome; furthermore, SWAP-200 Cluster B PD scores mediated the link between baseline binge eating and purging symptoms and therapy outcome, whereas scores in Clusters A and C showed no significant effects. The findings suggest that personality-based outcome research may improve treatment effectiveness in this difficult-to-treat population.