[An exploratory study of a personality disorders questionnaire].Encephale 2008; 34(5):517-25E
This exploratory study combined a preliminary evaluation of the French version of Hyler's [Hyler S.E. Personality Questionnaire (PDQ-4 plus). New York: New York State Psychiatric Institute; 1994] Personality Diagnostics Questionnaire (PDQ-4 plus) with an investigation into whether Eysenck's personality dimensions allow us to differentiate between subjects diagnosed by the PDQ-4 plus as showing at least one personality disorder (PD) and control subjects.
A group of 129 French undergraduate students completed the PDQ-4 plus, a self-report questionnaire designed to assess the 12 PDs of the DSM-IV (10 PDs and two additional diagnoses included in the appendix of the DSM-IV), and, at the same time, the Eysenck Personality Questionnaire Revised-Abbreviated (EPQ RA).
The PDQ-4 plus diagnoses were scored using a two-stage process in which students with questionnaire scores at or above the threshold level for at least one PD (82 students=63.56%) were asked to complete individual interviews about the PDs concerning them. In order to minimize the number of false positives generated, these interviews were scored using the Clinical Significance Scale. Following these interviews, 35 students (27.13%) were classified as showing one or more PDs. The remaining 84 students (72.87%) were classified as control subjects (no PDs). In the population as a whole, studies have shown the prevalence of any DSM-IV defined personality disorder to be between 9 and 15%; however, personality disorders are much more frequently diagnosed in younger subjects (Ekselius L., Tillfors M., Furmark T., & Fredrikson M. Personality disorders in the general population: DSM-IV and ICD-10 defined prevalence as related to sociodemographic profile. Personality and Individual Differences, 2001, 30: 311-320). The second step in the study was to compare EPQ RA scores for the control subjects, subjects showing a particular PD and subjects showing the other PDs.
For all the PDs studied, the control subjects attained lower scores on the Neuroticism scale than the subjects showing one or more PDs. Subjects showing depressive or schizotypal PDs attained particularly high scores on the Neuroticism scale: a result that differentiates these subjects from the control subjects and from subjects showing other PDs. Scores on the Extraversion scale were similar for all the subjects with the exception of those showing depressive or schizotypal PDs. Subjects with a depressive or a schizotypal PD were generally more introverted than the control subjects and the subjects showing other PDs. Significant differences between all three groups of subjects were noted on the Psychoticism scale, at least for the PDs studied here. Psychoticism scale scores were generally higher for the subjects showing one or more PDs than for the control subjects, except in the cases of the subjects showing compulsive-obsessional and paranoiac PDs, whose Psychoticism scores were not significantly different from those of the control subjects. The Psychoticism scores for the subjects with antisocial (cluster B) or schizotypal (cluster A) PDs were statistically higher than the scores for the control subjects and for the subjects showing other PDs. In summary, Neuroticism was more prevalent among the subjects showing depressive and schizotypal PDs. In terms of extraversion, only subjects showing depressive and schizotypal PDs could be differentiated from the control subjects and from the subjects showing other PDs. Psychoticism was more prevalent amongst the subjects showing depressive and schizotypal PDs.
In order to verify the results of this preliminary study, which was carried out using a relatively small group of subjects, this work must be replicated using a larger and more representative group of subjects.