Assessing Interpersonal Aspects of Schizoid Personality Disorder: Preliminary Validation Studies

Abstract

In 2 studies, we examined the reliability and validity of an interpersonal measure of schizoid personality disorder (SZPD) based on nonverbal behaviors and interpersonal interactions occurring during interviews. A total of 556 male jail inmates in the United States participated in Study 1; 175 mentally disordered offenders in maximum security hospitals in the United Kingdom participated in Study 2. Across both samples, scores on the Interpersonal Measure of Schizoid Personality Disorder (IM–SZ) exhibited adequate reliability and patterns of correlations with other measures consistent with expectations. The scale displayed patterns of relatively specific correlations with interview and self-report measures of SZPD. In addition, the IM–SZ correlated in an expected manner with features of psychopathy and antisocial personality and with independent ratings of interpersonal behavior. We address implications for assessment of personality disorder.

Acknowledgments

The research and preparation of this article were supported in part by Grants MH49111 and MH57714 from the National Institute of Mental Health to David S. Kosson, by a grant from the Special Hospitals Service Authority to Ronald Blackburn, and from the State Hospital, Scotland, to John P. Donnelly. We thank Patrick Firman and Charles de Filippo and the staff of the Lake County Jail in Waukegan, Illinois for their consistent cooperation and support during the conduct of this research. We also thank Carolyn Abramowitz, Maria Banderas, Nick Doninger, Seoni Llanes-Macy, Andrew Mayer, Sarah Miller, Elizabeth Sullivan, Marc Swogger, and Zach Walsh for interviewing the inmates and administering the measures used in Study 1. Finally, we are grateful to Roland Freese for helpful discussions about schizoidia and psychopathy and to Gordon Claridge, Lee Anna Clark, Carl Gacono, J. R. Meloy, Adrian Raine, and Kirsten Rasmussen for suggestions about interpersonal manifestations of schizoid PD.

Notes

The International Classification of Diseases (ICD–10; World Health Organization, [WHO], 1992) category of SZPD is quite similar but with a more explicit emphasis on the preference for fantasy and introspection.

Recently, Collins, Blanchard, and Biondo (2005) demonstrated in a community sample that IM–SZ scores correlated uniquely with social anhedonia scores after controlling for IPDE scores. That study provides preliminary evidence for construct validity of the IM–SZ. However, that study was not used to inform the predictions of this study, as data for these studies were collected prior to those of Collins et al.

∗ p < .01.

∗∗ p ≥ .001.

The Z test for independent correlations (Rosenthal & Rubin, 1982) revealed that the partial correlation for the relation between IM–SZ scores and scores on PCL–R Item 7, shallow affect, was greater for European Americans (r = .43) than for African Americans (r = .23), Z = 2.45, p = .01.

^a The Z test for dependent correlations indicated significant differences in the magnitude of the correlation for the IM–SZ than for the IPDE SZPD scale, all Zs > 2.27, ps < .05.

∗p ≤ .05.

∗∗ p < .01.

∗∗∗ p ≤ .001.

^aThe Z test for dependent correlations indicated larger correlations for the IPDE SZPD scale than for the IM–SZ, all Zs > 2.27, ps < .05.

∗p < .05.

∗∗ p ≤ .01.

∗∗∗ p < .001.