Long-term impact of residual symptoms in treatment-resistant depression.

Objective: Although commonly encountered, little work has defined the longitudinal course of treatment-resistant depression (TRD) and the influence of residual posttreatment symptoms on longer-term outcome. The aim of our study was to assess the impact of posttreatment clinical states on longer-term outcome.

Method: Patients (n = 118) with TRD received specialist inpatient treatment and were followed-up for a median of 3 years. Longitudinal outcome dichotomized into good and poor outcome was used as the primary outcome and functional measures were used as secondary outcomes.

Results: Among 118 treated patients, 40 (34%) entered clinical remission, 36 (31%) entered partial remission, and 42 (37%) remained in episode at discharge. At follow-up, 35% had longitudinally defined poor outcome. Posttreatment clinical status was the main predictor of both poor and good outcome. Nearly 50% of patients achieved postdischarge recovery, and subsequently had longer-term outcome, comparable with patients discharged in remission. Patients who remained in episode posttreatment were more symptomatically and functionally impaired.

Conclusion: Posttreatment clinical states are a useful guide to clinicians for projecting the longer-term outcome of patients with TRD. The persistence of residual or syndromal symptoms predicts a poorer longer-term outcome, whereas treatment to remission is associated with better outcomes.