Onset of Depression Inventory (ODI)—Assessment of the speed of onset of depressive episodes

Abstract

The development of a full blown depressive episode may be very rapid, taking less than one hour, or be very slow, taking up to months. In a previous study with outpatients it was found that the majority (58%) of depressive episodes within bipolar affective disorders (BD) develop within one week whereas this is rarely the case (7.4%) in unipolar depression (UD). Apart from a replication of these findings, the present study aimed to investigate the speed of onset in patients with BD compared to UD patients with either a depressive episode (DE) or recurrent depressive disorder (RD). Speed of onset of depression was assessed using the structured patient interview "Onset of Depression Inventory" (ODI). In total, 24 BD patients, 42 patients with a DE and 80 patients with a RD within unipolar affective disorders were included. The speed of onset of depressive episodes differed significantly between the three patient groups (Kruskal-Wallis-test: Chi²=12.493, p=0.002): 50% of the BD patients developed a depressive episode within a week, compared with only 16.7% of DE patients and 25.0% of RD patients. The ODI has not yet been validated. The earlier finding of a faster onset of depressive episodes in BD compared to UD patients is replicated. Clinicians should consider the possibility of a hidden bipolarity in patients who develop a depressive episode within a few days.