Inventory of interpersonal problems: a three-dimensional balanced and scalable 48-item version

Interpersonal relating has been a focus of attention in psychiatry for decades. To address this domain, a self-rating scale, the Inventory of Interpersonal Problems (IIP; Horowitz, Rosenberg, Baer, Ureño, & Villaseñor, 1988), was developed. Analysis of the psychometric properties of IIP presented in this article was performed by principal component analysis (PCA) for the purpose of obtaining subscales with a balanced, bipolar dimensionality. The model was validated by the resulting dimensions' ability to discriminate among different categories of personality disorders (PDs). The problem of a General Complaint factor affecting PCAs of questionnaires such as the IIP is discussed thoroughly, and ways of avoiding the problem are outlined. We present a three-dimensional structure of the IIP with both theoretically appealing and statistically robust dimensions of Assertiveness, Sociability, and Interpersonal Sensitivity based on 48 (out of 127) items. Balanced, additive indexes using the subset of 48 items appeared psychometrically sound by showing much lower correlations internally and less confounding from the General Complaint factor than extant indexes derived from the IIP. External validity seemed to be bolstered by all subscales' discriminating significantly between different PDs versus no PDs, on both cluster and single diagnosis levels. Our analysis seemed to substantiate the reliability (scalability) of three dimensions of the IIP tapping different areas of the interpersonal relational field.