Schröder 2013.

Methods	Study design: randomised controlled trial
Participants	Diagnosis: multiple somatoform symptoms Method of diagnosis: participants ≥ 18 years of age with at least 2 somatoform symptoms according to IDCL (for DSM‐IV). For each recorded symptom, the researchers checked whether there was substantial suffering or impairment. A medical evaluation was performed by a physician to exclude medically explained symptoms Exclusion criteria: medically explained symptoms, serious concentration or language problems, suicidal tendencies, psychotic symptoms Total number randomised: 173 (134 actually started treatment, lower numbers in Zaby 2008) Age: for intention‐to‐treat sample (n = 134) M = 48.02 years (SD = 12.34) (no baseline imbalances between study groups) Sex: for intention‐to‐treat sample (n = 134) 76.9% women (n = 103), 23.1% men (n = 31) (no baseline imbalances between study groups) Severity of symptoms at baseline: number of symptoms M = 9.9 (SD = 5.5) Duration of symptoms at baseline: ≥ 6 months Setting: participants were consecutively recruited in co‐operation with primary care physicians, psychotherapists, and by advertisements in local newspapers in the southwest of Germany Treatments were conducted in the outpatient treatment centre for psychological intervention at the University of Landau and the University of Mannheim, Germany Location: Landau and Mannheim region, Germany Number of treatment centres: 2 Co‐morbidities: Panic disorder: for intention‐to‐treat sample 20.1% (n = 27) Social phobia: for intention‐to‐treat sample 9.0% (n = 12) Specific phobia: for intention‐to‐treat sample 6.0% (n = 8) Generalised anxiety: for intention‐to‐treat sample 10.4% (n = 14) Major depressive disorder: for intention‐to‐treat sample 18.7% (n = 25) Adjunctive therapy: participants were free to seek further care Adjunctive medication: participants were free to seek further care
Interventions	Participants were randomly assigned to either 1. CBT (n = 49) Duration: manualised group training with 8 weekly sessions of 90 minutes in 8 groups of 4‐11 members Treatment protocol: the CBT used in this study was developed on the basis of theoretical considerations (Deary et al. 2007) and standardised guidelines for psychological therapy of somatoform disorders, as published elsewhere (Rief 1999; Rief 2002; Sharpe 1992). The manual contained detailed guidelines for conducting each session. Aim of treatment was to create a model to understand bodily discomfort, with integrated biological, psychological and social factors (see Zaby 2008, table 1 for extended information about the group sessions). Therapist: psychological psychotherapists who were supervised regularly 2. Progressive muscle relaxation (n = 41) Duration: manualised group training with 8 weekly sessions of 90 minutes in 11 groups of 4‐11 members Treatment protocol: the progressive muscle relaxation treatment was based on modifications of Jacobson's original program by Bernstein and Borkovec, following a manual (Zaby 2008). It involved learning to tense and relax groups of muscles beginning with a large number of small groups (in this case 16) and then proceeding in steps to a smaller number of large groups (first 7, then 4 groups) (for details, see Schröder 2013, page 299) Therapist/face‐to‐face contact: psychological psychotherapists who were supervised regularly 3. Waiting list control (excluded from analysis, as participants in waiting list group were not randomly assigned) Duration: NA Treatment protocol: participants with a waiting time for the intervention longer than 4 weeks, less than 3 months were included in the waiting list group Therapist/face‐to‐face contact: NA
Outcomes	Time points for assessment: baseline, directly post‐treatment (8 weeks) and 6 months after baseline Primary outcome: 1. Intensity and number of symptoms (SOMS‐7) Secondary outcome: 1. Depression (HADS‐D) 2. Anxiety (HADS‐A) 3. Physical and mental health (SF‐12, PWB, and MWB subscale) 4. Medical care utilisation in previous 6 months (interview at baseline and 6 months)
Notes	Date of study: participants were recruited from April 2005 until May 2006. Treatments were conducted between April 2005 and October 2008 Funding source: the study was supported by a grant awarded to Annette Schröder by the German Research Foundation (DFG) Declarations of interest among the primary researchers: none reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants were randomised for CBT or PMR using random sequences, exact method not described. When both groups were full, newly included participants were included in the waiting list group. As this group was not randomly assigned we excluded data from this group from analysis
Allocation concealment (selection bias)	Low risk	The randomisation was performed by a person who was not involved in assessment or treatment delivery
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Participants could not be blinded. Blinding of personnel not described
Blinding of outcome assessment (detection bias) All outcomes	High risk	Participants were not blinded, and most outcomes were participant reported
Incomplete outcome data (attrition bias) All outcomes	High risk	In both intervention groups 23% of participants dropped out before the first treatment (> 20%)
Selective reporting (reporting bias)	Low risk	All intended outcomes reported
Treatment fidelity	Low risk	CBT and PMR were conducted as a manualised group training (Schröder 2013, treatment conditions)
Researcher allegiance	Low risk	No indication that researchers had a preference for 1 of the treatment modalities
Other bias	Unclear risk	Participants were randomised for CBT or PMR. When both groups were full, newly included participants were included in the waiting list group. In a later stage, these participants were included in both intervention groups. (source: email contact with author) As participants are their own control participant due to this method, we decided to exclude data from the waiting list group from analysis