A psychometric validation analysis of Eysenck’s Neuroticism and Extraversion Scales in a sample of first time depressed patients.

Eysenck and Eysenck identified the two-factor structure of personality, namely
neuroticism and extraversion which has been widely used in clinical psychiatry, and generated much research on the psychometric properties of the scales. Using a classical psychometric approach the neuroticism and extraversion scales have shown robust psychometric properties. The present study used both classical psychometric and item response theory (IRT) analyses to evaluate the neuroticism and extraversion scales and improve scalability of the instrument neuroticism and extraversion. A first time depressed sample completed the Eysenck Personality Questionnaire (EPQ) and Hamilton Depression Rating Scale (Ham-D 17-item) at baseline and at follow-up five years later.
For the neuroticism scale a subscale containing depression-related symptoms, a
subscale containing anxiety-related symptoms, and a subscale containing symptoms related to interpersonal sensitivity were identified. For the extraversion scale a shorter and psychometrically more robust version was identified together with a short introversion scale.
Clinically discriminant validity was analysed using correlations. The correlation
between depression (Ham-D-17) and neuroticism-anxiety was below clinical
significance, while the correlation of depression (Ham-D-17) was above clinical significance for both interpersonal sensitivity and neuroticism-depression. Clinically discriminant validity was modest for the extraversion/ introversion subscales, however, the introversion subscale approached clinical significant correlation with depression.
The identified subscales of the EPQ, neuroticism-anxiety, interpersonal sensitivity, neuroticism-depression, extraversion and introversion are psychometrically valid measures of type and severity of the stress response. Using these subscales, it is possible to perform a quick and psychometrically valid evaluation of the type and severity of the stress response. The subscales may be useful in predicting types of psychopathology and in identifying underlying vulnerability that could serve as specific treatment targets in preventing as well as treating depression and anxiety.