Mixed-state bipolar i and II depression: Time to remission and clinical characteristics

Background We compared the time to achieve remission and the clinical characteristics of patients with bipolar depressive mixed state and those with bipolar depressive non-mixed state. Methods The subjects (N=131) were inpatients diagnosed between 2006 and 2012 with bipolar I or II disorder, depression and were classified into the following three groups: "pure depressive state" (PD, n=70), "sub-threshold mixed state" (SMX, n=38), and "depressive mixed state" (DMX, n=23). Diagnosis of a DMX was in accordance with Benazzi's definition: three or more manic symptoms in a depressive episode. The subjects' charts were retrospectively reviewed to ascertain the time to achieve remission from the index episode and to identify other factors, such as demographic and clinical characteristics, specific manic symptoms, and pharmacological treatment, that may have contributed to remission. Results The time to achieve remission was significantly longer in the DMX (p=0.022) and SMX (p=0.035) groups than in the PD group. Adjustment for covariates using a Cox proportional hazards model did not change these results. Clinically, subjects with a DMX were more likely to have manic symptoms in the index episode, especially inflated self-esteem and psychomotor agitation than those in the PD. Limitations We investigated only inpatients and therefore could not comment on outpatients. Conclusions These findings showed that sub-syndromal manic symptoms in bipolar depression had different clinical characteristics and a more severe illness course, including a longer time to achieve remission, than did a pure depressive state.