Information processing in chronic fatigue syndrome: the role of cognitive bias and negative illness cognitions in the perpetuation of symptoms of chronic fatigue

This thesis investigated cognitive biases in attention, interpretation, and memory and their role in symptom perpetuation of Chronic Fatigue Syndrome (CFS). The first empirical study presented in the thesis used a quasi-experimental design to explore the interaction of attention and a cognitive state of rumination in 33 people with CFS and 33 healthy controls, who were randomly assigned to undergo either rumination or distraction cognitive state induction. In these altered cognitive state participants have completed a visual probe task measuring attentional processes. The CFS group did not show attentional bias towards illness-related information following the rumination induction, compared to the CFS group in the distraction state or healthy controls. However, being in a state of either rumination or distraction led to greater mood volatility in CFS group than in healthy controls. The second empirical study similarly used a quasi-experimental design to investigate the interaction of attention and mood in a sample of 16 people with CFS, 25 people with asthma, and 28 healthy controls. The study explored later-stage conscious allocation of attention in neutral or depressive mood, under either low or high cognitive load. CFS, asthma and healthy control participants were randomly allocated to a depressive or a neutral mood induction. Then the participants completed two cognitive tasks, a visual probe (high load) and an exogenous cueing (low load), to measure allocation of attention towards health-threat. Attentional bias towards health-threat emerged under the condition of high cognitive load and neutral mood in CFS and healthy controls, but not in the asthma group. Depressive mood did not exert an influence on attentional bias towards health-threat in CFS. The third empirical study, using a quasi-experimental design, investigated later-stage conscious allocation of attention towards activity and exertion-related stimuli in the conditions of neutral and depressive mood, and low and high cognitive load, utilising the same method as the second empirical study, described above. The same sample of participants consisting of 16 people with CFS, 25 asthma and 28 healthy controls completed a visual probe and an exogenous cueing task to measure allocation of attention towards activity words and pictures. Under high cognitive load CFS group showed increased attentional avoidance of activity-related stimuli, compared to healthy controls. Empirical Study 4 investigated the process of interpretation of ambiguous information collecting and analysing the data from the sample of 33 people with CFS and 33 healthy control volunteers who also participated in Study 1. The study used a quasi-experimental design. The participants completed a lexical decision task, which measured their reaction times to the presentation of ambiguous information that could be interpreted either in a threatening or in a neutral manner. The CFS group did not demonstrate a tendency to interpret ambiguous information in a negative illness-related fashion, compared to the healthy control group. The fifth study, a survey conducted via the Internet, utilised a mixed methods design to investigate features of autobiographical memory, specificity and perspective, in 87 people with CFS, 56 people with asthma, and 60 healthy controls. Participants completed a memory task, where they were asked to recall four types of events (happy, pain, fatigue, physical activity), and questionnaires assessing symptoms, functioning, activity, mood, and coping. The CFS and asthma groups recalled more specific memories of activity, compared to healthy controls. For CFS and asthma groups general activity memories were associated with more personal, field memory perspective. The activity memories recalled by CFS group were rich and diverse in content, reflecting a complex multidimensional view of activity. Healthy controls viewed activity specifically as sport and exercise-related. Fatigue memories recalled by the CFS group reflected a stable, global, profound view of fatigue. The overall findings partially supported the hypothesis that people with CFS may cognitively over-process the information related to potential health-threat. Enhanced cognitive processing of health-threatening information may underpin increased monitoring and overperception of CFS symptoms. Methods that can address cognitive processing, for example reduce over-processing of potential health-threat or modify perception of activity, may be of benefit in treatments that aim to increase activity levels in people with CFS, such as Graded Exercise Therapy.