RESUMEN
OBJECTIVE: This study aimed to explore the associations between cognitions, behaviours and affects and fatigue in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME), and their relation to reduction of fatigue after cognitive behaviour therapy (CBT). METHODS: In CFS/ME patients, 22 behaviours, cognitions and affects, potentially perpetuating fatigue were registered 5 times a day using ecological momentary assessment (EMA) and an actigraphy. Simultaneous Components Analysis (SCA) was used to identify components of perpetuation, that were tested for their associations with fatigue in multilevel vector autoregressive (VAR) modelling. Fatigue severity was measured pre- and posttreatment with the Checklist Individual Strength. The relationship between perpetuation (the strength and direction of the possible associations between fatigue and the components) and therapy outcome was investigated. RESULTS: 58 patients met inclusion criteria (m age = 36.5; 65.5% female) and data of 50 patients were analysed in the multilevel analysis. Two perpetuating components were found: "psychological discomfort" and "activity". For the total group, both perpetuating components did not predict fatigue on a following time-point. For individual patients the strength and direction of the associations varied. None of the associations between perpetuating components and fatigue significantly predicted treatment outcome. CONCLUSION: Results suggest that there is heterogeneity in perpetuation of fatigue in CFS/ME. Investigating fatigue and perpetuators on an individual rather than group level could lead to new insights.