A prospective study of the impact of subthreshold mixed states on the 24-month clinical outcomes of bipolar I disorder or schizoaffective disorder

Objectives: The clinical significance of subthreshold mixed states is unclear. This study investigated the clinical outcomes in participants with bipolar I disorder or schizoaffective disorder, using the Cassidy and Benazzi criteria for manic and depressive mixed states, respectively. Methods: Participants (N = 239) in a prospective observational study of treatment and outcomes in bipolar I or schizoaffective disorder, bipolar type, were grouped based on study entry clinical presentation as having pure depression (n = 63) if they satisfied DSM-IV-TR criteria for a Major Depressive Episode (MDE), depressive mixed state if they also had at least three concurrent hypomanic symptoms (n = 33), or not depressed (n = 143) if they did not satisfy the criteria for MDE. Participants were similarly grouped as having pure mania (n = 3) if they satisfied DSM-IV criteria for a Manic Episode, manic mixed state if they also had at least two concurrent depressive symptoms (n = 33), or not manic (n = 203). Clinical data were collected by interview every 3 months over a 24-month period. Results: Measures of quality of life, mental and physical health over the 24-month period were significantly worse for participants who were classified as having mixed states at study entry on most outcome measures compared to participants who were not in an illness episode at study entry. A depressive mixed state was predictive of greater manic symptomatology over the 24 months compared to participants with pure depression. Conclusion: In participants with a current episode of mood disorder, the presence of subthreshold symptoms of opposite polarity was associated with poorer clinical outcomes over a 24-month period. © 2009 Elsevier B.V. All rights reserved.