Depressive Episodes: Is It Unipolar Depression or Bipolar Disorder?

Because of therapeutic and prognostic implications, clinicians hunger for ways to predict early on whether a depression portends unipolar or bipolar disorder. In an open, retrospective, cross-sectional study, investigators assessed the velocity of onset of depressive episodes in 215 German inpatients and outpatients with major depressive disorder, bipolar disorder, or recurrent depressive disorder. The researchers excluded 57 patients who had acute, critical life events immediately preceding the depressive episode, leaving data on 108 patients with major depressive disorder and 50 with bipolar disorder.

The onset of a full depressive episode within 1 week of initial symptoms occurred in 58% of bipolar patients and 7% of those with major depression. Median group differences in onset velocity between bipolar and unipolar groups were significant and remained so after exclusion of bipolar patients with switches from mania to depression. Onset was faster than 1 month in 92% of bipolar patients and slower than 1 month in 68% of unipolar patients. Duration, but not severity, of the episode correlated with velocity of onset. Speed of onset of the current episode and the preceding one correlated highly. Significantly more patients with very-rapid-onset depressions (≤3 days) than those with slow-onset depressions (≥1 month) showed loss of libido (85% vs. 46%) and suicidality (42% vs. 15%).