Mediation analysis shows that a decline in self-efficacy mediates the increase in fatigue severity following an initial positive response to cognitive behavioural therapy in Q fever fatigue syndrome.

Q fever fatigue syndrome (QFS) is characterized by chronic fatigue following acute Q fever. Previously, it was shown that cognitive behavioural therapy (CBT), and not doxycycline, was significantly more effective than placebo in reducing fatigue severity in QFS patients. However, this effect was not maintained after one year. The aim of this study is to elucidate the cognitive and behavioural variables which mediate the positive effect of CBT on fatigue during the treatment and the relapse of fatigue after completion of CBT, by using multiple mediation analysis.Additional analyses were performed on data of a randomized controlled trial that investigated the efficacy of CBT and antibiotics compared to placebo for QFS [1]. Only those patients in the CBT group who completed the allocated CBT treatment, and those patients in the medication group who did not follow additional CBT during follow-up, were included in this study. Two mediation models were tested, using respectively assessments at baseline and end-of-treatment (EOT), and EOT and follow-up, comparing the CBT group (n = 43) with the medication group (n = 89).During treatment, the decrease in fatigue brought on by CBT was completely mediated by an increase in self-efficacy with respect to fatigue. A reduction in self-efficacy partly mediated the increase in fatigue at follow-up in the CBT group.Given the decline in self efficacy, booster sessions focussing on restoration and maintenance of self-efficacy with respect to fatigue, may lead to elongation of the initial positive effects of CBT for QFS.