Hierarchical personality traits and the distinction between unipolar and bipolar disorders.

BACKGROUND The association between personality and psychopathology can provide an insight into the structure of mental disorders and the shared etiology and pathophysiology underlying diagnoses with overlapping symptomatology. The majority of personality-psychopathology research pertinent to the mood disorders has focused upon traits at the higher-order levels of the personality hierarchy, rather than those at intermediate or lower levels. The purpose of the current investigation was to investigate whether unipolar and bipolar mood disorders, and the severity of depressive and manic symptoms, show differential associations with traits at multiple levels of the personality hierarchy. METHODS Participants (N=275; 63% women; mean age 42.95 years) with depressive disorders (n=139) and bipolar disorders (n=136), as assessed by the Structured Clinical Interview for DSM-IV, Axis I Disorders, Patient Version (SCID-I/P; First et al., 1995), completed the Hamilton Depression Rating Scale, Young Mania Scale, Revised NEO Personality Inventory and Big Five Aspect Scales. RESULTS Results support the hypothesis that lower levels of the personality hierarchy provide additional differentiation of affective pathology. As compared to the widespread association of depressive symptoms with traits across the personality hierarchy, manic symptoms demonstrated more specific associations with traits at lower levels of the personality hierarchy. LIMITATIONS Patients with severe mania were excluded, thus the full range of mania is not represented in the current sample. CONCLUSIONS These results support the use of lower-order personality traits to discriminate between unipolar versus bipolar mood disorder, and are consistent with changes proposed to the psychiatric nosology to increase diagnostic precision.