Performance Validity and Outcome of Cognitive Behavior Therapy in Patients with Chronic Fatigue Syndrome

Jeroen J Roor*, Brechje Dandachi-FitzGerald, Maarten J. V. Peters, Hans Knoop, Rudolf W. H. M. Ponds

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


OBJECTIVE: There is limited research examining the impact of the validity of cognitive test performance on treatment outcome. All known studies to date have operationalized performance validity dichotomously, leading to the loss of predictive information. Using the range of scores on a performance validity test (PVT), we hypothesized that lower performance at baseline was related to a worse treatment outcome following cognitive behavioral therapy (CBT) in patients with Chronic Fatigue Syndrome (CFS) and to lower adherence to treatment.

METHOD: Archival data of 1081 outpatients treated with CBT for CFS were used in this study. At baseline, all patients were assessed with a PVT, the Amsterdam Short-Term Memory test (ASTM). Questionnaires assessing fatigue, physical disabilities, psychological distress, and level of functional impairment were administered before and after CBT.

RESULTS: Our main hypothesis was not confirmed: the total ASTM score was not significantly associated with outcomes at follow-up. However, patients with a missing follow-up assessment had a lower ASTM performance at baseline, reported higher levels of physical limitations, and completed fewer therapy sessions.

CONCLUSIONS: CFS patients who scored low on the ASTM during baseline assessment are more likely to complete fewer therapy sessions and not to complete follow-up assessment, indicative of limited adherence to treatment. However, if these patients were retained in the intervention, their response to CBT for CFS was comparable with subjects who score high on the ASTM. This finding calls for more research to better understand the impact of performance validity on engagement with treatment and outcomes.

Original languageEnglish
Article number1355617721000643
Pages (from-to)473-482
Number of pages10
JournalJournal of the International Neuropsychological Society
Issue number5
Early online date16 Jun 2021
Publication statusPublished - May 2022


  • Amsterdam short-term memory test
  • Chronic fatigue syndrome
  • Cognitive behavioral therapy
  • Effort
  • Performance validity
  • Treatment outcome

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