Subsyndromal depression is associated with functional impairment in patients with bipolar disorder

Background: The purpose of this study was to assess whether a relationship exists between mild depressive symptoms and overall functioning in subjects with bipolar disorder. Method: Twenty-five male subjects with bipolar I disorder (DSM-III-R criteria), who had not experienced a DSM-III-R episode of mania, hypomania, or major depression for 3 months as determined using the Structured Clinical Interview for DSM-III-R, were evaluated for degree of depressive symptoms using the Hamilton Rating Scale for Depression (HAM-D) and for overall functional status using the Global Assessment of Functioning (GAF, DSM-IV Axis V). Results: GAF scores were significantly negatively correlated with HAM-D scores (r = -0.61, df = 23, p = .001), despite the fact that no patient had a HAM-D score high enough to be considered clinically depressed. Conclusion: The results of this study support a relationship between subsyndromal depressive symptoms and functional impairment in bipolar subjects, despite their not meeting threshold criteria for a major depressive episode. These findings raise the possibility that in some patients with bipolar disorder subsyndromal depressive symptoms might contribute to ongoing functional impairment.