Cognitive factors in the maintenance of chronic fatigue syndrome

Abstract

Chronic Fatigue Syndrome (CFS) is an illness characterized by persistent debilitating fatigue of uncertain origin. Precipitating and perpetuating factors of this illness are thought to be distinct and the aim of this thesis was to gain greater insight into the role of cognitive factors which may maintain the condition. This work was guided by two central frameworks, the self-regulatory model of illness representations and the cognitive taxonomy of psychopathology. These were used to define the different cognitive constructs and to investigate the way they function as a system to maintain pathological schema and disability in CFS. Three studies using different methodologies were conducted to test the hypotheses. The first employed a descriptive comparative design to ascertain whether CFS patients have unique cognitions which contribute to their disability over time. The sample was comprised of CFS patients without depression (n=39), CFS patients with a concurrent diagnosis of depression (n=14), patients with a primary diagnosis of depression (n=20); and healthy controls (n=38). The groups were matched in aggregate for age, gender, race, and education. Subjects completed the Cognitive Errors Questionnaire-Revised, which measures cognitive distortions relevant to both general and somatic events, and the Illness Perception Questionnaire, which measures the five dimensions of the illness representation in conjunction with other standard measures. Between-group analyses confirmed that the depressed group was distinguished by a low self-esteem, feelings of guilt and self-recriminations, the propensity to make cognitive distortions across all situations, and to attribute their illness to internal, stable and global factors. In contrast, the CFS patients were characterized by low ratings of their current health status, a strong illness identity, external attributions for their illness, and distortion in thinking that were specific to somatic experiences. CFS depressed patients had lower self-esteem than non-depressed patients and had the most pessimistic illness beliefs. A six month follow-up showed that CFS patients' cognitive structures and level of disability remained remarkably stable. Illness identity, serious consequences, somatic errors, and limiting coping accounted for a substantial proportion of the variance in CFS patients’ disability scores over time. These results are discussed in terms of their support for both of the cognitive models. CFS patients appeared to have distinct cognitions which were associated with ongoing disability. The subsequent two quasi-experimental studies were conducted in a single laboratory session. The first of these used standardized neuropsychological tests to determine whether psychological variables, particularly somatic focus, interfere with CFS patients’ performance on high load attention tasks. The discrepancy between CFS patients’ subjective reports of concentration and memory difficulties and objective evidence of these deficits was also investigated. The subjects included 25 CFS patients matched for age, gender, and intelligence with two groups of healthy controls. One of these groups underwent a somatic induction procedure as part of the investigation of the effects of somatic preoccupation on attention tasks. The tests included the verbal memory subscales from the Wechsler Memory Scale-Revised and the Paced Auditory Serial Addition Task (PASAT), a measure of divided attention and speed of information processing. The analyses of the induction data failed to support the validity of this procedure resulting in the somatic control group being dropped from the analysis. Consistent with previous studies the principal deficit in the CFS group appeared to be on the PASAT. The CFS group appeared to be less accurate than healthy controls in their appraisal of their performance, which were related to negative mood rather than objective performance. Depression was also related to high performance expectations in the CFS group, but not the controls. The results did not support the original assumption that somatic preoccupation contributes to neuropsychological difficulties in CFS. However, mood factors were clearly shown to impact on both the objective and subjective experience of symptoms. The aim of the final study was to investigate the concordance between the self-report data collected in study one and information processing biases in CFS. Comparisons of the CFS patients and healthy controls on a modified Stroop attention task and a self-schema memory task, found no evidence of an illness-related bias in CFS patients’ processing of information. Rather, they demonstrated a significant tendency to be distracted by and remember depressed-relevant stimuli. The exception was their propensity to make somatic interpretations. These results are discussed in terms of the defensiveness hypothesis, which proposes that CFS patients’ negative, external illness perceptions and somatic distortions may act as a defence against underlying feelings of low self-esteem. The complex nature of CFS patients’ cognitive structures was revealed and the need to use measures which do not rely on self-reports was clearly demonstrated. These studies provided further support for the central role of cognitive factors and mood in perpetuating CFS.