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Transdiagnostic Therapy for Persistent Physical Symptoms: A mediation analysis of the PRINCE secondary trial

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Original languageEnglish
Article number104224
JournalBehaviour Research and Therapy
Early online date12 Nov 2022
Accepted/In press29 Oct 2022
E-pub ahead of print12 Nov 2022
PublishedDec 2022

Bibliographical note

Funding Information: The study was funded by Guy's and St. Thomas' Charity. Funding Information: TC, SL, KG and RMM acknowledge that this paper represents independent research part-funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust , King's College London and the NIHR Applied Research Collaboration South London (NIHR ARC South London) at King's College Hospital NHS Foundation Trust . The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. Publisher Copyright: © 2022 The Authors


King's Authors


The PRINCE secondary trial did not find any evidence that transdiagnostic cognitive behavioural therapy (TDT-CBT) plus standard medical care (SMC) was more efficacious than SMC for patients with Persistent Physical Symptoms (PPS) for the primary outcome Work and Social Adjustment Scale (WSAS) at final follow-up (52 weeks). There was a significant treatment effect for TDT-CBT plus CBT compared with SMC for two secondary outcomes: WSAS at the end of active treatment (20 weeks) and symptom severity (Patient Health Questionnaire, PHQ-15) at 52 weeks.

To understand mechanisms that lead to effects of TDT-CBT plus SMC versus SMC we performed a planned secondary mediation analysis. We investigated whether TDT-CBT treatment effects on these two secondary outcomes at the end of the treatment could be explained by effects on variables that were targeted by TDT-CBT during the initial phase of treatment. We pre-specified mediator variables measured at mid-treatment (9 weeks).

Reductions in catastrophising and symptom focusing were the strongest mediators of TDT-CBT treatment effects on WSAS at the end of treatment. Improvements in symptom focusing also mediated the effect of TDT-CBT on PHQ-15.

Future developments of the TDT-CBT intervention could benefit from targeting these mediators.

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