Differences in the ICD-10 diagnostic subtype of depression in bipolar disorder compared to recurrent depressive...

The aim of the study was to investigate whether patients with bipolar depression and patients with recurrent depressive disorder present with different subtypes of depressive episode as according to ICD-10.

All patients who got a diagnosis of bipolar affective disorder, current episode of depression, or a diagnosis of recurrent depressive disorder, current episode of depression, in a period from 1994 to 2002 at the first outpatient treatment or at the first discharge from psychiatric hospitalization in Denmark were identified in a nationwide register.

Totally, 389 patients got a diagnosis of bipolar disorder, current episode of depression, and 5.391 patients got a diagnosis of recurrent depressive disorder, current episode of depression, at first contact. Compared with patients with a diagnosis of recurrent depressive disorder, patients with bipolar disorder, current episode of depression, were significantly less often outpatients (49.4 vs. 68.0%), significantly more often got a diagnosis of severe depression (42.7 vs. 23.3%) or a diagnosis of depression with psychotic symptoms (14.9 vs. 7.2%). The rate of subsequent hospitalization was increased for patients with bipolar disorder, current episode of depression, compared with patients with a current depression as part of a recurrent depressive disorder (HR = 1.50, 95% CI = 1.20-1.86).

The results consistently indicate that a depressive episode is severer and/or more often associated with psychotic symptoms when it occurs as part of a bipolar disorder than as part of a recurrent depressive disorder.