Dimensional personality traits and treatment outcome in patients with major depressive disorder

Abstract

Background This study investigated the association between dimensional personality traits from the Five-Factor Model (FFM) and treatment outcome in patients with Major Depressive Disorder (MDD). Methods Six hundred forty-nine outpatients with MDD participated in a randomised double-blind longitudinal study for 6 months. Patients received a combination of medication and psychotherapy; they were randomised to medication condition (tianeptine or fluoxetine), and non-randomly assigned to psychotherapy condition (supportive, cognitive-behavioural, or psychodynamic). The Montgomery Asberg Depression Rating Scale was used to assess depression severity. The Système de Description en Cinq Dimensions was used to assess the personality domains of the FFM. Results Group comparisons revealed that patients who responded to both medication and psychotherapy had lower Neuroticism ( t = 4.22, p < .01), and higher Extraversion ( t = 4.01, p < .01) and Openness to Experience scores ( t = 3.57, p < .01) compared to non-responders. Regression analyses, which controlled for shared variance among the five personality domains, indicated that Neuroticism ( χ 2 = 4.06, p = .04) and Conscientiousness ( χ 2 = 8.98, p < .01) were significantly and uniquely associated with response. The two-way interactions between Neuroticism × Extraversion ( χ 2 = 4.49, p = .03) and Extraversion × Conscientiousness ( χ 2 = 5.91, p = .01) were also associated with response. These results were mostly replicated across the treatment-completer and intent-to-treat samples. Conclusions Dimensional personality traits predict response for individuals with MDD. Limitations This study did not examine facet-level traits, patient pre-morbid personality and functioning, and additional patient characteristics. Results may not be generalizable to severely depressed or treatment refractory patients.