Inventory of Interpersonal Problems-Personality Disorders: adaptation to Brazil and test of a bifactor model.

Objective: The Inventory of Interpersonal Problems-Personality Disorders (IIP-PD-47) has a controversial factor structure, as some studies have provided support for 5 correlated factors, and others have suggested the existence of a general second-order dimension. One approach of data modelling that reconciles multidimensionality and the existence of a general factor is the bifactor analysis. We used unrestricted exploratory-confirmatory bifactor modelling to validate the Brazilian version of the IIP-PD-47.

Methods: The sample consisted of 1,091 subjects aged 18-64 years who answered the IIP-PD-47 and a collateral measure of pathological traits, the Dimensional Clinical Personality Inventory 2 (IDCP-2).

Results: After testing many candidate models, our data were best represented by a bifactor model with one general factor and five specific uncorrelated factors. Nevertheless, a closer inspection of the discriminant validity of each IIP-PD-47 factor revealed strong support for the general factor and a factor capturing aggressive behaviours, but less support for the additional four specific factors.

Conclusions: The theoretical and practical implications of these findings are discussed, and some recommendations are offered about the need for controlling response styles when assessing PD traits via self-report inventories. Our findings indicate that the Brazilian version of IIP-PD has promising psychometric properties.