Background: Although there are effective psychological treatments for unipolar major depression in adolescents, whether or not one or more of the available therapies maintain reduced depressive symptoms 1 year after the end of treatment is not known. This is a non-trivial issue because maintaining lowered depressive symptoms below a clinical threshold level reduces the risk for diagnostic relapse into the adult years. Objective: To determine whether or not either of two specialist psychological treatments, cognitive-behavioural therapy (CBT) or short-term psychoanalytic psychotherapy (STPP), is more effective than a reference brief psychosocial intervention (BPI) in maintaining reduction of depression symptoms in the year after treatment. Design: Observer-blind, parallel-group, pragmatic superiority randomised controlled trial. Setting: A total of 15 outpatient NHS clinics in the UK from East Anglia, north-west England and North London. Participants: Adolescents aged 11-17 years with Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition major depression including those with suicidality, depressive psychosis and conduct disorder. Patients were randomised using stochastic minimisation controlling for age, sex and self-reported depression sum score; 470 patients were randomised and 465 were included in the analyses. Interventions: In total, 154 adolescents received CBT, 156 received STPP and 155 received BPI. The trial lasted 86 weeks and study treatments were delivered in the first 36 weeks, with 52 weeks of follow-up. Main outcome measures: Mean sum score on self-reported depressive symptoms (primary outcome) at final study assessment (nominally 86 weeks, at least 52 weeks after end of treatment). Secondary measures were change in mean sum scores on self-reported anxiety symptoms and researcher-rated Health of the Nation scales for children and adolescents measuring psychosocial function. Following baseline assessment, there were a further five planned follow-up reassessments at nominal time points of 6, 12, 52 and 86 weeks post randomisation. Results: There were non-inferiority effects of CBT compared with STPP [treatment effect by final follow-up =-0.578, 95% confidence interval (CI)-2.948 to 4.104; p = 0.748]. There were no superiority effects for the two specialist treatments (CBT + STPP) compared with BPI (treatment effect by final follow-up =-1.898, 95% CI-4.922 to 1.126; p = 0.219). At final assessment there was no significant difference in the mean depressive symptom score between treatment groups. There was an average 49-52% reduction in depression symptoms by the end of the study. There were no differences in total costs or quality-of-life scores between treatment groups and prescribing a selective serotonin reuptake inhibitor (SSRI) during treatment or follow-up did not differ between the therapy arms and, therefore, did not mediate the outcome. Conclusions: The three psychological treatments differed markedly in theoretical and clinical approach and are associated with a similar degree of clinical improvement, cost-effectiveness and subsequent maintenance of lowered depressive symptoms. Both STPP and BPI offer an additional patient treatment choice, alongside CBT, for depressed adolescents attending specialist Child and Adolescent Mental Health Services. Further research should focus on psychological mechanisms that are associated with treatment response, the maintenance of positive effects, determinants of non-response and whether or not brief psychotherapies are of use in primary care and community settings. Limitations: Neither reason for SSRI prescribing or monitoring of medication compliance was controlled for over the course of the study, and the economic results were limited by missing data.