The aims of COMET are the implementation and evaluation of effectiveness and cost-effectiveness as well as processes of a collaborative and stepped care model for depressive, anxiety, somatoform and/or alcohol abuse disorders within a multiprofessional network in comparison to routine care. In a cluster-randomized controlled effectiveness trial 570 patients will be recruited by 38 general practitioner practices and followed with a prospective survey at four time points. The primary outcome is the change in health-related quality of life from baseline to 6-months follow-up. Secondary outcomes include disorder-specific symptom burden, response, remission, functional quality of life, cost-effectiveness, evaluation of processes and other clinical and psychosocial variables.

Aims are a) the implementation and outcome evaluation, b) the process evaluation, and c) the analysis of the cost-effectiveness of an innovative collaborative and stepped care model for patients with depressive, anxiety, somatoform and/or alcohol abuse disorders.

Its novelty is the integration of these four disorders into one model. This approach is based on a) the high comorbidity between these disorders, b) the fact that they share a common etiological and diag-nostic basis, c) that similar evidence-based treatment options exist for them (e.g., self-help and psychoeducation, psychotherapy, pharmacotherapy), and d) that health care providers need to manage them together very often.

The conceptual basis follows the principles of evidence-based medicine with a specific focus on guideline implementation and the principles of patient-centered care including access, coordination and continuity of care, patient information, patient involvement and empowerment. Based on a multi-professional cooperation of health care providers across different care sectors an integrated health care network consisting of general practitioners (GPs), mental health specialists (psychiatrists, psychotherapists) and inpatient facilities will be established. Evidence-based clinical practice guidelines and pathways of care with treatment options of varying intensity form the clinical and procedural basis of the network, including low-intensity treatments and e-mental health technologies.

The study is planned as a randomized controlled effectiveness trial of a consecutive sample of patients with depressive and/or anxiety and/or somatoform and/or alcohol abuse disorders drawn from primary care (GP practices) and followed with a prospective survey at four time points. The study is intended to recruit a total of 570 patients from 38 GP practices. A cluster-randomization at the level of participating GP practices divides GPs into the intervention group, where patients are treated within a multi-professional collaborative and stepped care approach (including low-intensity treatments, direct access to mental health specialists, inpatient care etc., COMET), and the control group, where patients receive standard care (treatment as usual, TAU). Data collection is carried out with questionnaires as well as telephone interviews at four time-standardized measurement points within one year (baseline, 3, 6, 12 and 24 months). Additionally, independent research assistants perform standardized diagnostic interviews (CIDI) with patients at baseline to allow an assessment of diagnostic validity.

The main research hypothesis is that the COMET model is more effective than TAU. Primary outcome is the change in health-related quality of life measured by the SF-36 mental health score from baseline to 6-months follow-up. Secondary outcomes include symptom burden of depressive, generalized anxiety, panic, somatoform and alcohol abuse syndromes (PHQ-9; GAD-7; PHQ-15; PHQ panic and alcohol abuse syndrome module; SSD-12), disorder-specific response and remission, functional quality of life (EQ-5D-5L), duration of untreated illness, and other clinical and psychosocial variables (outcome evaluation, Work Package 1). Furthermore, direct and indirect costs and the incremental cost-effectiveness ratio will be assessed (economic evaluation, Work Package 2). Finally, feasibility and acceptance of the COMET model as well as of the different treatment components are assessed, including the implementation process (process evaluation, Work Package 3). To this end, semi-structured interviews will be conducted at two measurement points, supplemented by standardized surveys among involved patients and providers.

Inclusion Criteria:

• Inclusion criteria are a minimum age of 18, informed consent and one or more of the following positive ICD-10-diagnoses: depressive episode (F32), recurrent depressive disorder (F33), dysthymia (F34.1), agoraphobia (F40.0), social phobia (F40.1), panic disorder (F41.0), generalized anxiety disorder (F41.1), mixed anxiety and depressive disorder (F41.2), somatoform disorders (F45), and/or mental and behavioral disorders due to use of alcohol (F10.1, F.10.2)

Exclusion Criteria:

• Patients with insufficient knowledge of the German language, an acute psychosis or a health situation that does not allow questionnaire completion or patients already receiving current in- or outpatient psychiatric or psychotherapeutic care are excluded.