Table 2:

Evidence Grading System as recommended by the WFSBP (Hasan et al. 2019)

Evidence that the intervention is effective	Evidence statement phrasing	Level of evidence	Explanation
Strong	Should	A	At least two independent RCTs with a low risk of bias showing efficacy (superiority to placebo or, in the case of psychotherapy studies, superiority to an ‘active psychological placebo’ in a study with adequate blinding), OR Superiority to/equivalent efficacy compared with an established comparator treatment in a three-arm study with placebo control or in a well-powered non-inferiority trial (only applicable if such a standard treatment exists) with a low risk of bias, AND No negative RCTs with a low risk of bias exist. If there are contradicting results from RCTs, the majority of RCTs AND/OR a meta-analysis with low risk of bias, and that included studies that were generally at low risk of bias, showing efficacy. If there are more than one ‘A’ treatment options, the decision should be based on head-to-head comparisons or meta-analyses showing superiority of one of the treatments
Limited	Could	B	One RCT with a moderate risk of bias showing superiority to placebo (or in the case of psychotherapy studies, superiority to an ‘active psychological placebo’) OR A randomized controlled comparison with a standard treatment without placebo control with a sample size sufficient for a non-inferiority trial with a moderate risk of bias, AND No negative studies exist OR Meta-analyses with a moderate risk of bias that show efficacy or Meta-analyses with low risk of bias that included studies that were generally at a high risk of bias
Low	May	C1	One or more prospective open studies (with a minimum of 10 evaluable participants per group) using a control group, but no randomization, or using no control group, show efficacy OR One or more well-conducted case control or cohort studies (with a minimum of 10 evaluable patients) with a moderate probability that the relationship is causal show efficacy OR RCTs AND/OR meta-analyses with a high risk of bias showing efficacy
		C2	Non-analytic studies, e.g., case reports or case series with fewer than 10 evaluable participants show efficacy in the majority of cases
		C3	Expert opinions not based on any published data reporting efficacy
No Evidence		D

RCT, Randomized Controlled Trial