Clinical Associations Between Severity of Impulsivity, Psychiatric Morbidity, Dysfunctional Defences and Personality Disorder: A Comparative Study with Axis-I Disorders.

Objective: Psychiatric morbidity, impulsive behaviour and use of dysfunctional and maladaptive defences are core features of personality disorder (PD). This study aims to evaluate the significance of the strength of the association between these three core dimensions and PD. Method: Using a cross-sectional design, a sample of co-morbid Axis-I & -II disorders, and a sample of Axis-I disorders with no co-morbid PD were recruited at three general psychiatric mental health resource centres and then compared. PD as dependent variable was analysed both as a categorical and as a dimensional entity using the Structured Clinical Interview for DSM-IV. The Symptoms Checklist 90-R general severity index (GSI), the Barratt Impulsivity Scale (BIS) and the Defense Style Questionnaire (DSQ) were used to measure severity of psychiatric morbidity, impulsivity and defensive style, respectively. Results: BIS was a highly significant predictor of categorical PD (beta = .13, SE = .03, p < .001), but not GSI and DSQ. BIS and GSI significantly predicted PD as a dimensional construct (beta = 0.32, SE = .08, t = 4.05, p < 0.001; and beta = 5.04, SE = 1.54, t = 3.28, p = 0.002, respectively). The diagnostic efficiency statistics found that BIS had greater sensitivity (.82) and specificity (.79), and overall predictive power (.87) of correctly identifying true positive and true negative PD diagnosis compared to the other two measures. Conclusions: BIS may be used in routine clinical practice as a screening measure to identify the presence of PD in complex presentations.