The effect of prolonged duration of untreated depression on antidepressant treatment outcome

BackgroundThe duration of untreated illness has been considered a likely predictor of the course of psychotic disorders. However, there is only sparse data concerning the influence of treatment delay on the outcome of mood disorders. The present study aimed to assess the effect of prolonged untreated depression on the outcome of antidepressant treatment.MethodPatients aged 18-70 years with recent onset of the first lifetime depressive episode were systematically recruited by the Danish Psychiatric Central Research Register during a 2-year period. A total number of 399 individuals out of 1006 potential participants in the Register were interviewed, and 270 fulfilled the inclusion criteria. The validity of the diagnosis, duration of untreated illness, remission on first-line antidepressant treatment and a number of covariates, including psychiatric co-morbidity, personality disorders and traits, stressful life events prior to onset, and family history of psychiatric illness, were assessed by structured interviews.ResultsThe remission rate was significantly decreased among patients with six months or more of untreated depression as compared to patients who were treated with antidepressant medication earlier after onset (21.1% versus 33.7%, OR=0.5, 95% CI 0.3 to 0.9, p=0.03). The negative influence of a prolonged DUI on the outcome did not seem confounded by any of a wide range of demographic and clinical variables.LimitationsThe outcome was evaluated retrospectively. The findings cannot be generalized to patients outside hospital settings.ConclusionInitiation of antidepressant treatment more than six months after onset of first episode depression reduces the chance of obtaining remission. The results emphasize the importance of early recognition and treatment of patients suffering from depression.