Aim: The overarching aims of the thesis were to identify clinical characteristics that predict the outcomes of depressed patients treated inclinical practice by ECT, and to elucidate the effectiveness of continuation ECT at preventing relapses and recurrences.Methods: The studies included a retrospective chart review, three studies based on a quality register for ECT, and a randomized controlled trial(RCT) examining the effectiveness of continued ECT.Results: The overall response rate to ECT was 80%. Patients with psychotic depression (89%), older patients (84%), and inpatients (83%) had the highest response rates. Patients with personality disorders (66%) and outpatients (66%) had the lowest response rates. With regard to patients on sick leave, 59%, 71% and 88% of patients regained occupational functioning 6, 12 and 24 months after ECT, respectively. The rate of hospitalisation after ECT was high, with rates of 25%, 34%and 44% 6, 12 and 24 months after ECT, respectively. The relapse rate was higher in patients that were taking benzodiazepines and lower in patients that were taking lithium.The relapse rate was significantly lower in patients treated with continued ECT in combination with pharmacotherapy (32%) than in those treated with pharmacotherapy alone (61%). This difference was particularly pronounced in medication-resistant patients (31% vs. 85%)Conclusions: The short-term response rate to ECT is relatively high in all patient subgroups, and is particularly high in older patients, inpatients and patients with severe depression. Patients often regain occupational functioning after ECT; however, this takes a considerably longer time than that required for symptom relief. Nevertheless, the relapse and recurrence rates of patients are high in the years after ECT. Continuation ECT and lithium treatment can be combined with antidepressants to reduce the risk of relapse and recurrence. Further RCTs are required to define the indications for continuation ECT and lithium treatment.