Exploring the role of psychological flexibility in the management of fatigue-related disability in rheumatic disease

Fatigue is one of the most debilitating symptoms of rheumatic disease. Despite advances in medical treatments, fatigue persists for many people with rheumatic disease and remains a major contributor to functional disability. Fatigue is believed to be caused, exacerbated, and/or maintained by a collection of biopsychosocial factors. Psychological treatments for rheumatic disease-fatigue have been trialled but have had limited success. Further research on the mechanism of such interventions is needed to develop suitable approaches. The aim of this thesis was to evaluate the relevance of the psychological flexibility model to the management of fatigue-related disability among people with rheumatic disease, guided by the Medical Research Council framework for developing complex interventions. I followed a three-stage process of development. First, I conducted a systematic review to evaluate the effectiveness of Acceptance and Commitment Therapy (ACT) – a treatment based on the psychological flexibility model – for people with rheumatic disease. Second, I conducted a broad qualitative study for two reasons: a) to develop a deeper understanding of the meaning of fatigue, its impact on people with rheumatic disease, and what characterises fatigue that is unmanageable and requires intervention; and b) to understand participants’ perspectives on completing a daily diary questionnaire designed to measure psychological flexibility and fatigue. Third, after ensuring that daily diary methods are a suitable way of collecting data on psychological flexibility and its processes, I conducted a daily diary study to evaluate the relationship between daily psychological flexibility and fatigue-related disability in people with rheumatic disease. In the systematic review, I concluded that ACT improves physical and emotional functioning in people with fibromyalgia, but there was a lack of evidence pertaining to other forms of rheumatic disease or fatigue. These findings signalled a need for further development work. In the qualitative study, I found that although people with rheumatic disease may report substantial fatigue, it was their descriptions of how fatigue impacts their daily activities that signalled a need for intervention. Further findings from the qualitative study indicated that daily diary methods were acceptable to participants, and participants’ feedback informed the development of the subsequent daily diary study. The measures developed for the daily diary study had acceptable reliability and validity, and the excellent response rate indicated daily diary methods are an acceptable way to collect data on psychological flexibility and fatigue in this population. Findings from the daily diary study indicated that on days when people with rheumatic disease engaged in more valued activity and were more mindful, they reported lower levels of fatigue-related disability. This novel finding suggests that psychological treatments that increase valued activity and mindfulness may be useful for managing fatigue-related disability in rheumatic disease. Together, the findings of this thesis showed that the psychological flexibility model is relevant to fatigue-related disability in rheumatic disease, identified differences between tiredness and fatigue in people with rheumatic disease, and led to the development of reliable and valid daily measures of valued activity, cognitive fusion, and mindfulness that can be used in future intervention studies that target these processes