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Table 2 Risk of bias assessment. Methodological quality: review author's judgment about each methodological quality item for each included study

From: The physiological and psychological effects of cognitive behavior therapy on patients with inflammatory bowel disease before COVID-19: a systematic review

References Random sequence generation (selection bias) Allocation concealment (selection bias) Blinding of participants and personnel (performance bias) Blinding of outcome assessment (detection bias) Incomplete outcome data (attrition bias) Selective reporting (reporting bias) Validated assessment instruments of outcome used§
McCombie et al. [51] + a b ?c + ?q +
Mikocka-Walus et al. [46] + d e ? + + +
Mikocka-Walus et al. [45] + d +e ? +  +  +
Wynne et al. [49] + f ? ? + + +
EVA Szigethy et al. [44] ? ? ? + + + +
Berrill et al. [50] + g ? ? + + +
Stapersma et al. [9, 48] + ? ?j +k +l + +
Stapersma et al. [47] + ? +m ? +l + +
Hunt et al. [42] + +n ? ? + ?q +
Levy et al. [43] + +o ? +p + +  + 
Thompson et al. [41] ? ? ? ? + + +
  1. +Low risk of bias
  2. −High risk of bias
  3. ?Unclear risk of bias
  4. The processing methods of attrition data are reported
  5. The outcome that stated in advance has been reported
  6. §Validated assessment tools were used for the assessment
  7. aParticipants were present when they were randomized
  8. bWithout blinding; all patients in the TAU group were aware of the CCBT patients receiving CCBT
  9. cThe author considered that blinding would not have improved the results in favor of the CCBT
  10. dParticipants are aware they may be offered an intervention or the placebo
  11. eGiven impossibility of blinding the intervention, we decided to withdraw the information regarding the intervention from the controls. Thus, the controls had been informed they participated in an observational study on mental health in IBD
  12. fThe author considered that it was not possible to blind participants to their allocated group. To minimize bias, an investigator not involved in recruitment or screening performed randomization, and participants completed all study questionnaires alone
  13. gParticipants were not blinded as to their allocation following randomization and there was no placebo therapy used in the control group
  14. hParticipants were not randomly assigned to groups
  15. iParticipant selection
  16. jOnly describes the independent curriculum and does not describe the implementation of the blind method in detail
  17. kV30% was rated on adherence by at least one rater, and of that 30%, half was evaluated by at least two raters (i.e. 15% of all sessions). Audiotapes were randomly selected to be rated by two of the raters; interrater agreement was globally calculated using Pearson’s correlation between two data columns with (1) all first ratings and (2) all second ratings for all patients and sessions combined
  18. lVery low attrition (< 3%)
  19. mThe interviewer and treating physicians had no access to the files in which the randomization result was described; the youth and their parents not to reveal the trial arm assignment to the interviewer and treating physicians; web-based questionnaires, to be completed at home
  20. nParticipants were allocated upon receipt of their consent and confirmation of eligibility by a research assistant, who assigned sequential participants based on the results of the coin toss. Thus, allocation was not predetermined and was concealed until assignment
  21. oParticipants were blind to their group assignment
  22. pTThis scale was then mailed back to the study office in a sealed stamped envelope and thus not seen by the therapist
  23. qOutcomes reported for completers only