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

BACKGROUND: 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.

SAMPLING AND METHODS: 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.

RESULTS: 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).

CONCLUSIONS: 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.