Purpose: This cross-sectional study aimed to compare the personality traits of patients with major depressive disorder (MDD) and bipolar disorder (BD) with those of healthy individuals. The goal was to gain insight into the potential impact of personality traits on the development and manifestation of mood disorders.
Methods: One hundred seventy-eight patients with mood disorders were analyzed as either MDD or BD, with each group containing euthymic and depressive members: e-MDD, d-MDD, e-BD, and d-BD. Mood status was assessed using the Young Mania Rating Scale (YMRS), and the 17-item Hamilton Depression Rating Scale (HAMD-17). Ninety-five healthy individuals served as controls. Personality traits were assessed with the Eysenck Personality Questionnaire.
Results: The scores for neuroticism in the patient groups were comparable, but each group had higher scores compared to the control group (P < 0.001). Each patient group exhibited significantly lower scores for extraversion compared to the control group, with e-MDD, d-MDD, and d-BD showing particularly notable differences (P < 0.001); these groups scored significantly lower than the e-BD (P = 0.041, 0.009, 0.038). In patients with BD, there was an inverted association between extraversion score and HAMD total score (P = 0.010, r = – 0.27), and a positive association with the YMRS total score (P = 0.022, r = 0.24). In the MDD group, there was a positive association between the neuroticism score and HAMD total score (P = 0.021, r = 0.25).
Conclusion: Patients with mood disorders are characterized by lower extraversion and higher neuroticism. Level of neuroticism associated with depression severity in MDD. Patients with BD may be more extraverted, but their extraversion can be affected by depressive episodes. Extraversion may be a feature of BD, and may differentiate BD from MDD. Personality traits are related to disease diathesis and state, and shaped by symptom manifestations.

Keywords: personality traits, mood disorders, neuroticism, extraversion