The Role of Cognitive Deficits in Borderline Personality Disorder with Early Traumas: A Mediation Analysis

(1) Background: although studies of cognitive functions are still limited in borderline personality disorder (BPD), the initial evidence suggested that BPD patients have deficits of executive functions and social cognition. In addition, patients who report physical and psychic traumatic experiences in childhood and adolescence show considerable neurocognitive impairment and severe BPD symptoms. The present study has a twofold aim: (1) to evaluate the differences in neurocognitive performances between BPD patients and healthy controls and (2) to verify in the BPD patients group whether neurocognitive deficits have the role of mediating the effect of early traumas on BPD psychopathology. (2) Methods: 69 subjects were enrolled: 38 outpatients with a diagnosis of BPD (DSM-5) and 31 healthy controls. BPD patients were tested with the Borderline Personality Disorder Severity Index (BPDSI), and the Childhood Trauma Questionnaire–Short Form (CTQ-SF). All subjects were evaluated with the Iowa Gambling task (IGT), the Berg card sorting test (BCST), the Tower of London task (ToL), and the Reading-the-mind-in-the-eyes-test (RMET). Statistical analysis was performed with the analysis of variance to compare the cognitive performances between BPD patients and controls. A mediation analysis was conducted with the Sobel Test in the BPD patients group. The significance level was p ≤ 0.05. (3) Results: significant differences between the two groups were found for several parameters of all the cognitive tests examined: BCST, IGT, ToL, and RMET. Mediation analysis with the Sobel test demonstrated that the percentage of correct answers in the BCST (BCSTc) and the RMET score significantly mediated the relation between the CTQ total score and BPDSI total score. (4) Conclusions: BPD patients showed an impairment of the following executive functions: set shifting, decision making, planning and problem solving, and social cognition abilities, in comparison with controls. Our results suggested that the effect of early trauma on BPD psychopathology was mediated by a deficit in two cognitive domains: cognitive flexibility and social cognition.