Acceptance and commitment therapy applied to early psychosis: Therapeutic foundations and a narrative systematic review

Table 4 Methodological quality appraisal of the randomized controlled trials

Domain/question	van Aubel et al[66]	Myin-Germeys et al[67]	Chien et al[69]	Özer and Dişsiz[7]	Chong et al[70]
Internal validity. Bias related to:
Selection and allocation
1. Was true randomization used for assignment of participants to treatment groups?	Y	Y	Y	Y	Y
2. Was allocation to treatment groups concealed?	U	Y	Y	Y	Y
3. Were treatment groups similar at the baseline?	Y	U	Y	Y	Y
Administration of intervention/exposure
4. Were participants blind to treatment assignment?	N	N	N	N	N
5. Were those delivering treatment blind to treatment assignment?	Y	Y	U	U	N
6. Were outcomes assessors blind to treatment assignment?	Y	Y	Y	N	U
Assessment, detection, and measurement of the outcome
7. Were treatment groups treated identically other than the intervention of interest?	Y	Y	Y	U	Y
8. Was follow up complete and if not, were differences between groups in terms of their follow up adequately described and analyzed?	Y	Y	Y	Y	Y
9. Were participants analyzed in the groups to which they were randomized?	Y	Y	Y	Y	Y
Participant retention
10. Were outcomes measured in the same way for treatment groups?	Y	Y	Y	Y	Y
Statistical conclusion validity
11. Were outcomes measured in a reliable way?	Y	Y	Y	Y	Y
12. Was appropriate statistical analysis used?	Y	Y	Y	Y	Y
13. Was the trial design appropriate, and any deviations from the standard RCT design accounted for in the conduct and analysis of the trial?	Y	Y	Y	Y	Y
Score	8	8	8	6	7

The classification follows the Joanna Briggs Institute checklist for methodological quality appraisal of randomized controlled trials[63]. Items 11 to 13 are not included in the overall score because they do not evaluate the internal validity. Y: Yes; U: Unclear; N: No.