title: Changes in illness perceptions mediated the effect of cognitive behavioural therapy in severe functional somatic syndromes.
abstract: OBJECTIVE
  Although there is substantial evidence that cognitive behavioural therapy alleviates symptoms in functional somatic syndromes, the mechanisms of change are less investigated. This study examined whether changes in illness perceptions mediated the effect of cognitive behavioural therapy.
  
  
  METHODS
  We analysed additional data from a randomised controlled trial comparing completers of cognitive behavioural group therapy (46 patients) to an enhanced usual care group (66 patients). Proposed mediators (illness perceptions) and primary (physical health) and secondary (somatic symptoms and illness worry) outcomes were assessed by means of questionnaires at referral, baseline, end of treatment, and 10 and 16 months after randomisation. Multiple mediation analysis determined whether (1) changes in specific illness perceptions during treatment mediated the effect of cognitive behavioural therapy (primary analysis), and (2) whether changes in illness perceptions during the whole trial period were associated with improved outcome (secondary analysis).
  
  
  RESULTS
  Improvements in illness perceptions during treatment partially mediated the effect of cognitive behavioural therapy on physical health one year after treatment (sum of indirect effects 1.556, BCa 95% CI (0.006; 3.620)). Improving perceived control was particularly important. Changes in illness perceptions from baseline to 16 months after randomisation were associated with clinically meaningful improvements in physical health, somatic symptoms and illness worry during the same period.
  
  
  CONCLUSIONS
  Our results suggest that changing patients' illness perceptions is an important process in cognitive behavioural therapy for functional somatic syndromes. Challenging patients' own understanding of their illness may hence be a key element of successful treatment.
authors.affiliation: The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Nørrebrogade 44, Aarhus C, Denmark.
authors.forename: Sara Sletten
authors.initials: SS
authors.lastname: Christensen
authors.affiliation: The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Nørrebrogade 44, Aarhus C, Denmark.
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Frostholm
authors.affiliation: The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Nørrebrogade 44, Aarhus C, Denmark.
authors.forename: Eva
authors.initials: E
authors.lastname: Ørnbøl
authors.affiliation: The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Nørrebrogade 44, Aarhus C, Denmark. Electronic address: andreas.schroeder@aarhus.rm.dk.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schröder
mesh_terms: D000328:Adult; D001007:Anxiety / Q000209:etiology; D015928:Cognitive Behavioral Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011602:Psychophysiologic Disorders / Q000523:psychology* / Q000628:therapy*; D012938:Social Perception; D011795:Surveys and Questionnaires; D013577:Syndrome; D016896:Treatment Outcome
keywords: Chronic fatigue syndrome; Cognitive-behavioural therapy; Fibromyalgia; Functional somatic syndromes; Illness perceptions; Mediation