Abstract
ObjectiveFatigue is a common symptom among cancer survivors that can be successfully treated with cognitive‐behavioral therapy (CBT). Insights into the working mechanisms of CBT are currently limited. The aim of this study was to investigate whether improvements in targeted cognitive‐behavioral variables and reduced depressive symptoms mediate the fatigue‐reducing effect of CBT.MethodsWe pooled data from three randomized controlled trials that tested the efficacy of CBT to reduce severe fatigue. In all three trials, fatigue severity (checklist individual strength) decreased significantly following CBT. Assessments were conducted pre‐treatment and 6 months later. Classical mediation analysis testing a pre‐specified model was conducted and its results compared to those of causal discovery, an explorative data‐driven approach testing all possible causal associations and retaining the most likely model.ResultsData from 250 cancer survivors (n = 129 CBT, n = 121 waitlist) were analyzed. Classical mediation analysis suggests that increased self‐efficacy and decreased fatigue catastrophizing, focusing on symptoms, perceived problems with activity and depressive symptoms mediate the reduction of fatigue brought by CBT. Conversely, causal discovery and post‐hoc analyses indicate that fatigue acts as mediator, not outcome, of changes in cognitions, sleep disturbance and depressive symptoms.ConclusionsCognitions, sleep disturbance and depressive symptoms improve during CBT. When assessed pre‐ and post‐treatment, fatigue acts as a mediator, not outcome, of these improvements. It seems likely that the working mechanism of CBT is not a one‐way causal effect but a dynamic reciprocal process. Trials integrating intermittent assessments are needed to shed light on these mechanisms and inform optimization of CBT.
Highlights
Cancer‐related fatigue is a distressing symptom that persists in around 25% of cancer survivors long after completion of their cancer treatment.[1,2] Cognitive‐behavioral therapy (CBT) is an evidence‐ based intervention for reducing cancer‐related fatigue.[3]
To overcome the limitations mentioned above, the current study investigated a comprehensive set of putative mediators that might explain the fatigue‐reducing effect of CBT and compares the results from the classical mediation analysis to those of causal discovery
Both the classical mediation analysis and the causal discovery confirmed that CBT leads to a significant reduction in fatigue
Summary
Cancer‐related fatigue is a distressing symptom that persists in around 25% of cancer survivors long after completion of their cancer treatment.[1,2] Cognitive‐behavioral therapy (CBT) is an evidence‐ based intervention for reducing cancer‐related fatigue.[3]. Changes in the targeted cognitive‐behavioral variables are assumed to explain the beneficial effect of CBT. In line with the cognitive‐behavioral model of fatigue, recent studies among cancer patients undergoing treatment for chronic myeloid leukemia[5] and advanced cancer[6] suggest that increased self‐ efficacy, reductions in helplessness and focusing on symptoms act as mediators of the fatigue‐reducing effect brought by CBT. Studies among cancer survivors[7,8,9] and patients on active treatment[10] found no evidence that increased physical activity, assessed objectively, explained the fatigue‐reducing effect brought by CBT. Studies on the putative mediating effect of other cognitive‐behavioral variables that are thought to maintain fatigue in cancer survivors, and are targeted in CBT, are currently lacking
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