It is unclear to what degree systematic exposure exercises contribute to the overall effects of exposure therapy (exposure and response prevention). This trial recruits individuals with high somatic symptom burden or reactivity to symptoms who, based on previous work, are likely to benefit specifically from exposure therapy. The aim of the study is to evaluate to what degree the effect of exposure therapy for this group is driven by the addition of structured exposure exercises to response prevention. This will be evaluated on the basis of a randomized controlled trial (N=360) where participants are enrolled either in response prevention (n=180), or exposure and response prevention (n=180). Primary outcome will be the between-group differences in the reduction in reactivity to symptoms, as measured week-by-week using the somatic symptom disorder B-criteria scale (SSD-12). Results from this project will be informative for exposure-based and various multicomponent behavioral treatments for individuals with persistent physical symptoms worldwide.
Persistent physical symptoms refers to somatic complaints that persist for months or more and give rise to significant distress, regardless of etiology. Common complaints such as gastrointestinal symptoms, fatigue, and pain have been estimated to account for up to half of primary care consultations, can be difficult to classify, and often defy straightforward medical explanation. In light of substantial personal and socioeconomic repercussions, effective clinical interventions are needed. The investigators recently completed a randomized controlled trial in primary care (SOMEX1) where individuals with persistent physical symptoms were randomized to 10 weeks of exposure therapy or healthy lifestyle promotion. Based on that trial, exposure therapy appears to have a small average advantage over healthy lifestyle promotion in mean effect on symptom preoccupation, i.e., the patient's tendency to respond strongly to, and engage in behaviors contingent on, somatic symptoms, and also on patient satisfaction. In line with a priori hypotheses, this added effect on symptom preoccupation was larger, and an advantage in the effect on somatic symptom burden was also seen, when patients reported a very high general somatic symptom burden or symptom preoccupation before treatment. For example, a patient with a PHQ-15 score of 10 could expect a near-zero added effect of exposure therapy on somatic symptom burden (d = 0.08) and a small added effect on symptom preoccupation (d = 0.31), whereas a patient with a PHQ-15 score of 15 could expect a small to moderate added effect on somatic symptom burden (d = 0.37) and a moderate added effect on symptom preoccupation (d = 0.62). An unexpected finding, however, was that in exposure therapy, the correlation between the participant's number of exposure exercises and reduction in symptom preoccupation was weak (rs=0.21-0.26). This highlights the fact that it is yet unclear to what degree the two main components of exposure therapy - exposure and response prevention - contribute to the treatment effects. It is also unclear what patient- and contextual factors moderate the added effect of exposure. The aim of the present project is to focus on the aforementioned subgroup of patients who benefit specifically from exposure therapy, and to determine to what degree this is driven by the addition of exposure to response prevention. This will be evaluated on the basis of a randomized controlled trial (N=360; SOMEX2) where participants with a high general somatic symptom burden or high symptom preoccupation are enrolled in response prevention (n=180), or exposure and response prevention (n=180). Primary outcome will be between-group differences in the reduction in symptom preoccupation as measured week-by-week using the somatic symptom disorder B-criteria scale (SSD-12). The participants will be blinded to the study design and the hypotheses of the investigators. Results from this project will be informative for exposure-based and various multicomponent behavioral treatments for primary care patients with persistent physical symptoms worldwide. \- Primary research question: Is there a significant average advantage, d≥0.30, of exposure and response prevention, as compared to response prevention only, with regard to the reduction in symptom preoccupation (SSD-12) up to the post-treatment assessment? Hypothesis: Yes. \- Key secondary research questions: Is the average advantage of adding exposure to response prevention moderated by the frequency of opportunities for response prevention as measured at baseline? Hypothesis: Yes, more opportunities are predictive of a smaller added effect of exposure exercises. Is the average advantage of adding exposure to response prevention moderated by the temporality of unwanted outcomes as measured at baseline? Hypothesis: Yes, more distal unwanted outcomes are predictive of a larger added effect of exposure exercises. Is the average advantage of adding exposure to response prevention moderated by anxiety sensitivity - i.e., reactivity to physiological arousal - at baseline? Hypothesis: Yes, a higher anxiety sensitivity is predictive of a larger added effect of exposure exercises. Which additional variables act as moderators and mediators of added effects (below)? Are there average advantages of adding exposure (superiority, ds≥0.30) with regard to general somatic symptom burden, core depressive symptoms, or functional impairment? Hypothesis: No. What is the cost-effectiveness of exposure and response prevention versus response prevention? Exploratory analyses.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
360
Exposure exercises, planned on the basis of functional analysis. Participants are encouraged to evaluate the relevance of-, and if so work continuously with-, interceptive, in vivo, and imaginal exposure exercises which are planned at specific timepoints.
Response prevention, planned on the basis of functional analysis. Participants make a plan to reduce presumably negatively reinforced behavior contingent on somatic symptoms and distress related to somatic symptoms.
Liljeholmen University Primary Health Care Centre
Stockholm, Sweden
Somatic Symptom Disorder-B Criteria Scale (SSD-12)
Theoretical range: 0-48. A higher score indicates higher degree of reactivity to symptoms.
Time frame: Change over the main phase, as modeled using data from all 11 assessments from the baseline assessment to the primary endpoint (≤45 days after treatment). Additional analyses incorporate 6- and 12-months follow-up assessments.
Somatic Symptom Scale 8 (SSS-8)
Theoretical range: 0-32. A higher score indicates a higher subjective somatic symptom burden.
Time frame: Change over the main phase, as modeled using data from all 11 assessments from the baseline assessment to the primary endpoint (≤45 days after treatment). Secondary analyses incorporate 6- and 12-months follow-up assessments.
GAD-7
Theoretical range: 0-21. A higher score indicates more general anxiety.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment). Additional analyses incorporate 6- and 12-months follow-up assessments.
Patient Health Questionnaire 9 (PHQ-9)
Theoretical range: 0-27. A higher score indicates more symptoms of depression.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment). Additional analyses incorporate 6- and 12-months follow-up assessments.
12-item WHO Disability Assessment Schedule 2.0 (WHODAS 2.0)
Theoretical range: 0-100. A higher score indicates more disability.
Time frame: Change over the main phase, as modeled using data from the baseline assessment and primary endpoint (≤45 days after treatment). Additional analyses incorporate 6- and 12-months follow-up assessments.
Seven questions probing into basic emotions related to somatic symptoms
For each emotion (anger, disgust, fear, joy, sadness, shame, surprise), theoretical range: 0-10. A higher score indicates presence of emotion.
Time frame: Change over the main phase, as modeled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
14-item Health Anxiety Inventory (HAI-14)
Theoretical range: 0-42. A higher score indicates more health anxiety.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
Adapted 11-item version of the Catastrophizing about Asthma Scale (CAS)
Domain-specific outcome, for participants with a mean score of at least 1 on the PHQ-15 cardiopulmonary domain. Theoretical range: 0-44. A higher score indicates more reactivity to cardiopulmonary symptoms.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
Reactivity to fatigue (study-specific)
Domain-specific outcome, for participants with a mean score of at least 1 on the PHQ-15 fatigue domain. Theoretical range: not yet finalized. A higher score indicates more reactivity to fatigue.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
Visceral Sensitivity Index (VSI)
Domain-specific outcome, for participants with a mean score of at least 1 on the PHQ-15 gastrointestinal domain. Theoretical range: 0-75. A higher score indicates reactivity to gastrointestinal symptoms
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
Pain Catastrophizing Scale (PCS)
Domain-specific outcome, for participants with a mean score of at least 1 on the PHQ-15 pain domain. Theoretical range: 0-52. A higher score indicates more reactivity to pain.
Time frame: Change over the main phase, as modelled using data from the baseline assessment and primary endpoint (≤45 days after treatment).
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