Objective: Although psychological treatments for patients suffering from medically unexplained physical symptoms (MUPS) show promising results, evidence for their effectiveness is still limited. The aim of this study was to review the existing empirical support for change mechanisms that explain treatment effect in terms of symptom intensity and symptom interference in the daily lives of patients.
Methods: A systematic database search was conducted. Sixty-seven eligible studies were found, and change mechanism effects were extracted from them. The data were subjected to a systematic review.
Results: Fifteen change mechanisms were identified. Those receiving the most consistent support included Increasing symptom acceptance, Development of coping strategies, and Positive treatment expectations, although the last mechanism was investigated in only two studies. Almost all mechanisms received support for at least one type of outcome, either at post-treatment or at follow-up.
Conclusions: Although some empirical support exists for many mechanisms, some of them have received only marginal attention in empirical studies. These limitations prevented us from deriving more definite conclusions.
Keywords: Change mechanism; Mediator; Medically unexplained physical symptoms; Psychological treatment; Systematic review.
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