Effects of a positive psychological intervention on mood and physical health in adults with diabetes and those at low or high risk

Objectives: Positive Affect (PA) has been shown to influence a range of diabetes outcomes, including glycaemic control, mood, and self-management and preventative behaviours (Pressman, Jenkins, & Moskowitz, 2019). Positive Psychological Interventions (PPIs) are designed to facilitate PA, and several have demonstrated that they are effective when applied to a diabetes context for promoting physical and psychological outcomes. The aim of this PhD had been to build upon existing research and theory to specifically apply the ‘Best Possible Self’ (BPS) PPI to people with, and at risk of, diabetes. Design: This thesis utilised a mixed-methods approach to 1) assess acceptability and feasibility of the BPS amongst people with Type 1 (T1D) and Type 2 (T2D) diabetes, and to; 2) tease out the intervention’s mechanisms in a diabetes context using a non-clinical sample of participants at low and medium-high risk of T2D. Methods: Five studes were conducted using one-to-one interviews, focus groups, self-report measures, textual analysis, and physiological methodologies. Results: Acceptability and feasibility results demonstrated that the BPS had potential as a PPI for people with T1D and T2D. It was well-received by participants, and the quantitative findings showed that it influenced perceptions of self-care. However, the results also highlighted the need for further investigation of the intervention’s mechanisms. Using a non-clinical sample of people at various risk of T2D, Studies 2 through 5 revealed the BPS’ true relationship with PA in this context, while showcasing intervention benefits to diabetes-related symptomatology, feelings of autonomy, perceived stress, resilience, and blood pressure. Conclusions: The research reported within this thesis demonstrates that PPIs may indeed be an effective way of producing a variety of positive health outcomes not only in people with T1D and T2D but also in those at various risk of T2D. This work also highlights the need to consider the unique needs of people with, at risk of, diabetes. Future work should assess outcomes over a longer period (e.g. six months, one year, five years) while being mindful of moderating factors such as T2D risk.