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Improving the care of people with diabetes and severe mental illness

Dorey, T. (2024). Improving the care of people with diabetes and severe mental illness. (Unpublished Doctoral thesis, City, University of London)



There is an increased prevalence, morbidity, reduced quality of life and excess mortality in adults with a severe mental illness (SMI) and type 2 diabetes (T2D). While the origins of these disparities are multifaceted, health care system and delivery factors emerge as a noteworthy contributing element.


The aim of this PhD was to develop a theoretically informed and evidence-based behaviour change intervention to support improved T2D care for adults with an SMI.


This PhD consists of five studies. A systematic review (Study 1) of the perceived barriers and enablers of delivery and organisation of T2D care for adults with an SMI. A theoretical congruence assessment (Study 2) of existing interventions targeting health professional delivery of T2D care. The design of an intervention informed by the 8 steps of the Behaviour Change Wheel. A Delphi study (Study 3) with 21 service users, health professionals, and carers supported completion of steps 1 -3 to identify and specify a behaviour target(s). A qualitative interview study (Study 4) with 10 health professionals which through a deductive (using Framework Analysis) and inductive analysis (using Codebook Thematic Analysis) identified the important domains of the Theoretical Domains Framework to be targeted in a resulting intervention. Final steps 5-8 of the Behaviour Change Wheel were completed through mapping exercises, existing literature, and a Delphi study (Study 5) with 6 mental health professionals resulted in a draft intervention strategy.


The expansive systematic review of 28 studies, consisting of 2,243 participants identified that health professionals perceive barriers to the provision of T2D care for adults with an SMI across individual, interpersonal, and organisational levels. The domains Environmental Context and Resources, Social influence, Social/professional role and identity, Knowledge, Skills, Goals and Beliefs about capabilities were identified as important determinants. Existing interventions were limited in number (n=8) but targeted many of the identified domains. It was identified however that there was scope to expand on existing interventions by considering a wider range of theoretically congruent intervention content, ensuring more detailed intervention descriptions, and developing rigorous evaluations. The INDEX guidance and the eight steps Behaviour Change Wheel were used to guide the development of a theoretically informed and evidence-based intervention over three studies. It was identified that T2D care for adults with an SMI could be improved by focussing on 1) HbA1c monitoring, 2) provision of lifestyle advice and 3) referral, delivered during relapse of severe mental illness by mental health nurses working in community mental health teams. Across all three target behaviours eight domains were identified as important. The centrality of social/professional role and identity and the need to shift responsibility was highlighted. Intervention development resulted in the selection of 6 intervention functions, 3 policy categories, and 14 behaviour change techniques which were combined into four overarching intervention strategies - 1) a training session, 2) appointment of a T2D relapse champion, 3) goals and feedback and 4) changes to care planning and the environment.


This PhD has provided a clear understanding of the perspectives and priorities of service users, carers, and health professionals resulting in a novel, evidence-based and theory-informed intervention. The intervention strategies collectively aim to improve the knowledge and skills of mental health nurses, enhance teamwork and support systems, set goals, and provide feedback, and modify the care planning process and environment to facilitate the provision of three target behaviours (1. HbA1c monitoring, 2. referrals and 3. lifestyle advice) during a relapse of SMI. Whilst these strategies demonstrate promise it is important to consider contextual factors such as staff readiness for change, the emotional response to feedback and the overall context of community mental health care. Ongoing evaluation and refinement of these strategies will be needed and can be progressed through post-doctoral feasibility testing.

Publication Type: Thesis (Doctoral)
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Q Science > Q Science (General)
R Medicine
R Medicine > RT Nursing
Departments: School of Health & Psychological Sciences > Nursing
School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses
Doctoral Theses
[thumbnail of Dorey thesis 2024 redacted PDF-A.pdf]
Text - Accepted Version
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