Symptoms of depression as possible markers of bipolar II disorder

Underdiagnosis and misdiagnosis of bipolar-II disorder (BP-II) as a major depressive disorder (MDD) are frequently reported. The study aim was to find which symptoms of depression could be possible cross-sectional markers of BP4-II, in order to reduce underdiagnosing BP-H. Methods: Consecutive 379 BP-II and 271 MDD major depressive episode (MDE) outpatients were interviewed with the Structured Clinical Interview for DSM-IV, the Hypomania Interview Guide, and the Family History Screen, by a senior psychiatrist in a private practice. Inside-MDE hypomanic symptoms (elevated mood and increased self-esteem always absent by definition) were systematically assessed. Mixed depression was defined as an MDE plus 3 or more inside-MDE hypomanic symptoms, a definition validated by Akiskal and Benazzi. Results: The MDE symptoms significantly more common in BP-II versus MDD were weight gain, increased eating, hypersomnia, psychomotor agitation, worthlessness, and diminished ability to concentrate. The inside-MDE hypomanic symptoms significantly more common in BP-II were distractibility, racing/crowded thoughts, irritability, psychomotor agitation, more talkativeness, increased risky and goal-directed activities. Multiple logistic regression showed that hypersomnia, racing/crowded thoughts, irritability, and psychomotor agitation were independent predictors of BP-II. Irritability had the most balanced combination of sensitivity and specificity predicting BP-H. Psychomotor agitation had the highest specificity but the lowest sensitivity. Racing/crowded thoughts had the highest sensitivity but the lowest specificity. These symptoms had a similar positive predictive value (PPV) for BP-II, which was around 70% (PPV is more clinically useful than sensitivity and specificity), which in turn was similar to the PPV of mixed depression and atypical depression (two diagnostic clinical markers of BP-II). All possible combinations of these symptoms had a PPV similar to that of the individual symptoms. The validity as BP-II markers of these symptoms was supported by a significant association with bipolar family history. Conclusions: Hypersomnia, racing/crowded thoughts, irritability, and psychomotor agitation may be useful, cross-sectional markers of BP-II. Finding these symptoms in depression should lead the clinician to careful probing for history of hypomania, which should reduce the BP-II misdiagnosed as MDD. Results may also have treatment impacts, as antidepressants used alone (i.e., no concurrent mood stabilising agent) in BPII depression misdiagnosed as MDD may increase cycling. (c) 2005 Elsevier Inc. All rights reserved.