Background: Impaired psychological health in type 1 diabetes is prevalent and associated with elevated glycaemic outcomes. International evidence-based guidelines have defined glycaemic treatment targets to prevent acute and long-term complications. In addition, the guidelines encourage screening for the elevated distress that living with type 1 diabetes may imply. There is a need to gain further understanding of what it means to live with type 1 diabetes as an adult with elevated HbA1c and to develop interventions to promote psychological and physiological health.

Aim: The overall aim of the thesis was to describe experiences of living with type 1 diabetes as an adult with elevated HbA1c and furthermore to evaluate the impact of an Acceptance and Commitment Therapy programme for people living with type 1 diabetes. The thesis also aimed to examine the Swedish version of Acceptance and Action Diabetes Questionnaire (AADQ), which is a questionnaire for psychological flexibility related to diabetes.

Method and result: In Study I we included 81 adults with type 1 diabetes and HbA1c > 60 mmol/mol in a randomised controlled trial. A seven-session programme based on Acceptance and Commitment Therapy was conducted and the impact on HbA1c, self-management and psychosocial factors was evaluated. No effect was demonstrated in the linear mixed model analysis on HbA1c or the secondary outcomes. Nevertheless, a significant statistical improvement in psychological flexibility was noted one and two years after the intervention. A large drop-out rate was observed in the study. In Study II, the psychometric properties of a translated version of the AADQ were examined through Rasch analysis. A total of 120 adults with type 1 diabetes were included. The Swedish version of the ADDQ showed acceptable psychometric properties such as fit to the Rasch model and person separation index. However, we also found indications on a malfunctioning categorisation of the response categories. A collapsed three category rating was examined. In Study III, two categories of experiences were described in the qualitative interviews: constraining and manageable. Through content analysis, an overarching theme was created "a life-long follower". The theme describes the unrelenting existence of type 1 diabetes that impact life in various degrees.

Conclusion: No impact on HbA1c or secondary outcomes could be demonstrated through the Acceptance and Commitment Therapy based programme. At the same time, a key component in psychological health, psychological flexibility, was improved. The Swedish version of the AADQ showed acceptable psychometric quality. However, uncertainties regarding the categorisation should be further examined. The experiences of living with type 1 diabetes as an adult and elevated HbA1c is widely diverse. A person-centred care approach is therefore crucial to support the needs of each unique person with type 1 diabetes.