Replicating the five factor model of personality in a psychiatric sample

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Abstract

In this study we examined whether the factor structure and traits of the five-factor model of personality (FFM), derived from non-clinical samples, could be replicated in a sample of psychiatric patients. The revised NEO Personality Inventory (NEO PI-R) was administered to a study group of psychiatric patients (n=176). The test scores from these patients were intercorrelated, factor analyzed and the obtained factor structure was then compared to the factor structure of the normative data from the NEO PI-R. The factor structure from the psychiatric study group and that from the normative sample were virtually identical, with all five factors showing significant congruence. These results argue favorably for the clinical applicability of the FFM with psychiatric patients.

Introduction

Two primary approaches to the classification of personality psychopathology exist. The categorical approach, exemplified best by the DSM Axis II disorders conceptualizes personality disorders as maladaptive clusters of traits that are clear departures from `normal' personality. The dimensional approach, represented predominantly by the five-factor model of personality (FFM) (Digman, 1990), posits that there is a continuous relationship between adaptively healthy and maladaptive personality traits. In this model personality disorders are conceptualized as extreme and, therefore, dysfunctional variants of traits that are present in all persons.

The FFM has gained recognition as a valid model for use in psychiatric samples. The dimensions composing the FFM: neuroticism (N), extraversion (E), openness-to experience (O), agreeableness (A) and conscientiousness (C) have demonstrated diagnostically meaningful associations with several different Axis I patient groups (Bagby et al., 1997). The dimensions of the FFM have also been demonstrated to be more consistent with the Axis II personality disorder configuration than other dimensional models of personality (O'Connor & Dyce, 1998). Substantial heritability coefficients for the five personality dimensions of the FFM have also been reported (Jang, Livesley, & Vernon, 1996) and a recent study indicated that the effects of acute illness (Santor, Bagby, & Joffe, 1997) did not influence greatly these personality dimensions.

It has not yet been demonstrated, however, that the most fundamental property of the FFM, the factor structure itself, accurately describes personality in psychiatric populations. The replication of the FFM factor structure with a study group of psychiatric patients is important. Such a replication would demonstrate, at least in part, that the same personality dimensions that can accurately describe healthy persons are able to characterize psychiatric patients. The primary aim of this study was to assess the generalizability of the traits and structure of the FFM in a diagnostically heterogeneous group of psychiatric patients. It was hypothesized that the factor structure representing the traits of the FFM as measured by the revised NEO Personality Inventory (NEO PI-R) (Costa & McCrae, 1992) in a healthy normative sample could be replicated in a sample of psychiatric patients.

Section snippets

Method

Subjects were 176 psychiatric patients (43 schizophrenics, 43 bipolar disorder patients and 90 patients with major depression). Diagnosis for all patients was established using the Structured Clinical Interview for Axis I, DSM-IV disorders (First, Spitzer, Gibbon, & Williams, 1995). The mean age of the sample was 39.2 years (S.D.=10.3). Patients were administered the NEO PI-R as part of other research protocols. All patients provided written informed consent prior to their participation.

The NEO

Results

Compared to the normative sample (who, by statistical definition, have an average score of 50T and a standard deviation of ten), all three patient groups scored high on N (Mean=65.87; S.D.=14.72), low on E (Mean=41.35; S.D.=12.87) and C (Mean=41.32; S.D.=11.53). For O and A, the mean T scores were in the `average' range. For O, (Mean=48.99; S.D.=9.72); for A (Mean=47.08; S.D.=12.49). In sum, on three of the five personality dimensions of the FFM, the psychiatric study group scored at least one

Discussion

The results from this study provide evidence of the internal reliability and factor replicability of the FFM in psychiatric samples. For three of the five dimensions of the FFM the patients' scores differed by more than one standard deviation from the normative samples. This result, along with the replicabilty of the factor structure, supports the contention the dimensions of the FFM are represented in psychiatric samples as extreme variants of `normal' dimensions of personality.

Although the

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