Change in fatigue in acceptance and commitment therapy-based treatment for chronic pain and its association with...

Fatigue is commonly reported by people with chronic pain. The purpose of the current study was to examine Acceptance and Commitment Therapy (ACT), based on the Psychological Flexibility (PF) model, for fatigue in chronic pain.

This study included 354 adults attending an interdisciplinary ACT-oriented treatment for chronic pain. T-tests and analyses of clinically meaningful change were used to investigate participant improvements in fatigue interference after the treatment. Pearson's correlations and hierarchical regressions were conducted to investigate associations between improvement in fatigue interference and improvements in PF processes. Finally, mixed effects models were used to explore associations between baseline fatigue interference and changes in treatment outcome measures.

Participants improved in fatigue interference (d = 0.37), pain, some PF processes and daily functioning (d = 0.18-1.08). 39.7% of participants demonstrated clinically meaningfully improvements in fatigue interference. Changes in fatigue interference was associated with changes in pain, PF processes and daily functioning, |r| = 0.20-0.46. Change in fatigue interference was associated with change in pain acceptance independent of change in pain, β = -0.36, p < .001. However, baseline fatigue interference did not predict any treatment outcome. Overall, people with fatigue appeared to benefit from the ACT-oriented interdisciplinary treatment for chronic pain, and relatively higher levels of fatigue did not appear to impede this benefit.

ACT-based treatments may benefit people with chronic pain and fatigue. Future studies including experimental designs, and studies investigating other PF processes, are needed to better understand the utility of ACT for comorbid fatigue and pain.

This study investigates the association between fatigue interference and psychological flexibility processes in chronic pain, and the first one investigating fatigue interference as a predictor of functioning in chronic pain following Acceptance and Commitment Therapy (ACT)-based treatment. Findings of the study provide preliminary evidence for the association between ACT and fatigue in people with chronic pain and support the potential benefit of ACT for people with comorbid chronic pain and fatigue.