*M*ulti-morbidity in *O*lder Adults with *D*epression *S*tudy (MODS)

Aim. Develop a feasible, acceptable, clinical and cost-effective intervention to improve physical and mental functioning in older adults with mental-physical multimorbidity including depression. Objectives: 1. Develop a feasible collaborative care intervention for older people with depression and long term conditions (LTCs). 2. Conduct an external pilot trial to establish trial procedures and refine our intervention for the target population. 3. Conduct a fully powered, definitive trial of the clinical effectiveness and cost utility of the intervention. 4. Develop a framework to inform post-trial implementation of the intervention across provider settings and staff. Rationale Multimorbidity in older people is a clinical priority with complex but adaptable interventions required to offer effective treatment across the care pathway. In response to this priority, we propose the multimorbidity in older adults MODS programme of research. We will develop and evaluate an intervention which addresses the co-existence of the most common mental disorder (depression) alongside physical ill health. Depression and long term conditions (LTCs) commonly exist together; the outcome of LTCs is worse if depression is present [1]. We have promising evidence that by offering integrated physical-psychological care, depressive and functional symptoms can improve. We propose to refine and evaluate the use of collaborative care and a brief psychological intervention (behavioural activation) for older people with mental-physical multimorbidity drawing upon our prior research (trials and systematic reviews) in this area. Our programme follows the MRC complex interventions framework [2]. We will adapt and refine a complex intervention (with an already-established randomised evidence base) for use in a new population (older adults with mental-physical multimorbidity). WS1 Adapting and developing the collaborative care/behavioural activation intervention for people with mental-physical multimorbidity Collaborative care with behavioural activation has a robust evidence base amongst older people with depression. We will iteratively adapt our existing self-help materials from earlier trials for older people with depression using a mix of interviews, consensus groups and case studies. Our intervention is based upon a well-evidenced, theoretically-informed behavioural intervention delivered within a collaborative primary care framework. We will develop a manualised treatment protocol with training materials/programme. WS1 output: A manualised collaborative care intervention that addresses functional limitations and depressive symptoms amongst older people with mental physical multimorbidity. WS2 MODS external pilot-trial with concurrent qualitative evaluation Having developed our collaborative care intervention, we will conduct a pilot study to ensure our materials and the interventions are fit for purpose [3] to deliver a complex intervention to our target primary care population with mental-physical multimorbidity. We will use a stand-alone external pilot-RCT to assess optimum methods of recruitment, retention and intervention delivery. WS2 outputs: (1) the final manualised collaborative care behavioural intervention which is fit for purpose , (2) clear parameters and procedures to enable the MODS programme to conduct a fully-powered trial of clinical effectiveness and cost utility. WS 3 MODS pragmatic randomised controlled trial In a fully powered trial we will establish the clinical effectiveness and cost-utility of a collaborative care intervention for older people with physical-mental comorbidity. We will use a pragmatic design to ensure maximum generalisability to real world primary care settings. We will use a patient reported outcome measure (PROM) as our primary outcome, in order to judge the value of collaborative care resul