Objectives: Our primary aim was to describe unique correlates of functioning in bipolar disorder (BD).
Experimental design: The study included the first 500 patients enrolled in the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). Patients were 41.9 +/- 12.7 years old, and diagnosed with bipolar I, II or NOS, verified by structured interview. Overall functionality was determined by the Range of Impaired Function Tool (LIFE-RIFT). Stepwise multiple regression analysis tested the non-redundant-independent-association of 28 variables on functioning.
Principal observations: Severity of depression symptoms was significantly and uniquely correlated with impaired functioning in the context of a wide variety of demographic and clinical variables, contributing 60.9% to the total variance in overall functioning (ss = 0.254, p = 0.0001). Substantial variance in function remains unexplained.
Conclusions: Intensity of depressive symptoms is the major determinant of impaired functioning in bipolar disorder, but longitudinal analyses may further explain the substantial variance in function not explained by this large and comprehensive model. Treatments and outcome assessment for patients with bipolar disorders should consider both functional and symptomatic change.