Relationships of neuroticism and extraversion with axis I and II comorbidity among patients with DSM-IV major depressive disorder

Abstract

Background High comorbidity with axis I and II disorders among major depressive disorder (MDD) patients may in part be due to the predisposing personality dimensions of neuroticism and extraversion. However, a comprehensive view of this relationship is lacking. Methods MDD patients ( n = 193) in the Vantaa Depression Study were interviewed at baseline and at 6 and 18 months with the SCAN and SCID-II, and a general population comparison group ( n = 388) surveyed by mail. Neuroticism and extraversion were measured with the Eysenck Personality Inventory. A dose–exposure relationship between standardized levels of neuroticism and extraversion and type and number of comorbid axis I and II disorders among patients with MDD was hypothesized. Results Prevalence and number of comorbid axis I and II disorders increased significantly with increasing level of neuroticism. In contrast, as the level of extraversion increased, the prevalences of social phobia and cluster C personality disorders decreased. Patients with pure MDD or with any comorbid axis I or II disorder had z-scores of neuroticism of + 0.46, + 0.90 and + 1.30 and of extraversion of − 0.34, − 0.47 and − 0.84, respectively. Limitations Patients' personality scores were not pre-morbid. Conclusion Among MDD patients, a positive dose–exposure relationship appears to exist between neuroticism and prevalence and number of comorbid axis I and II disorders. A negative relationship exists between level of extraversion and prevalence of social phobia and cluster C personality disorders. These findings are consistent with the hypothesis that high neuroticism and low extraversion predispose to comorbid axis I and II disorders among patients with MDD.