The Ego Impairment Index and schizophrenia: a validation study

This study is an extension of our work on a new scale, the Ego Impairment Index (EII; Perry & Viglione, 1991). The index is theoretically based on Beres's (1956) model of ego assessment and was empirically developed on a sample of melancholic, depressed outpatients, diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (3rd ed. [DSM-III]; American Psychiatric Association, 1980). The EII is derived from the Rorschach Inkblot Test and offers a single composite score of ego impairment. This study validates the use of the EII with a heterogeneous sample of schizophrenic patients. In support of the trait-like characteristics of the scale, the EII continues to be expressed as a single factor, with a correlation of .98 when comparing the original factor derived from a melancholic population with this sample of schizophrenic patients. Significant correlations were also found between the EII and other clinical indices, including the Magical Ideation Scale, the Schizophrenia Index, and the Minnesota Multiphasic Personality Inventory (MMPI). Finally, the EII was found to differentiate between a paranoid subgroup and a mixed undifferentiated/disorganized subgroup who theoretically have more ego impairment. These results offer support for the use of the EII as an empirical means of quantitatively and qualitatively assessing thought disorder within a theoretical framework. Further research is needed to understand the application of the EII across different diagnostic groups and its relationship to other indices of psychological disturbance.