Objective: Important differences exist between bipolar disorder with and without comorbid anxiety, but little is known about the long-term prognostic significance of coexisting anxiety in bipolar disorder. The authors sought to identify the anxiety features most predictive of subsequent affective morbidity and to evaluate the persistence of the prognostic relationship.
Method: Probands with bipolar I or II disorder from the National Institute of Mental Health Collaborative Depression Study were followed prospectively for a mean of 17.4 years (SD=8.4) and were characterized according to various manifestations of anxiety present at baseline. A series of general linear model analyses examined the relationship between these measures and the proportion of follow-up weeks in episodes of major depression and in episodes of mania or hypomania.
Results: Patients whose episode at intake included a depressive phase spent nearly three times as many weeks in depressive episodes than did those whose intake episode was purely manic. Psychic and somatic anxiety ratings, but not the presence of panic attacks or of any lifetime anxiety disorder, added to the predictive model. Combined ratings of psychic and somatic anxiety were associated in a stepwise fashion with a greater proportion of weeks in depressive episodes, and this relationship persisted over the follow-up period.
Conclusions: The presence of higher levels of anxiety during bipolar mood episodes appears to mark an illness of substantially greater long-term depressive morbidity.