BackgroundAround 40 per cent of patients with unipolar depressive disorder who are treated in secondary care mental health services do not respond to first or second line treatments for depression. Such patients have 20 times the suicide rate of the general population and treatment response becomes harder to achieve and sustain the longer they remain depressed. Despite this there are no randomised controlled trials of community based service delivery interventions delivering both algorithm based pharmacotherapy and psychotherapy for patients with chronic depressive disorder in secondary care mental health services who remain moderately or severely depressed after six months treatment. Without such trials evidence based guidelines on services for such patients cannot be derived.Methods/designSingle blind individually randomised controlled trial of a specialist depression disorder team (psychiatrist and psychotherapist jointly assessing and providing algorithm based drug and psychological treatment) versus usual secondary care treatment. We will recruit 174 patients with unipolar depressive disorder in secondary mental health services with a Hamilton Depression Rating Scale (HDRS) score ≥ 16 and global assessment of function (GAF) ≤ 60 after ≥ 6 months treatment. The primary outcome measures will be the HDRS and GAF supplemented by economic analysis incuding the EQ5 D and analysis of barriers to care, implementation and the process of care. Audits to benchmark both treatment arms against national standards of care will aid the interpretation of the results of the study.DiscussionThis trial will be the first to assess the effectiveness and implementation of a community based specialist depression disorder team. The study has been specially designed as part of the CLAHRC Nottinghamshire, Derbyshire and Lincolnshire joint collaboration between university, health and social care organisations to provide information of direct relevance to decisions on commissioning, service provision and implementation.Trial registrationClinical trials.gov identifier NCT01047124