Classification of the level of evidence for treatment interventions.

1+	High quality RCTs* and their MA/SR
1	Other RCTs and their MA/SR
2	Prospective cohort studies, their MA/SR, (predefined) RCT sub analysis
3	Non-randomized controlled trials, before and after studies, retrospective cohort studies, case-control studies, and their MA/SR and RCT post hoc sub-analysis
4	Cross-sectional studies, case series
Consensus	Consensus of the members of the JAS guideline committee.

RCT: randomized controlled trial, MA: meta-analysis, SR: systematic review

* A high-quality RCT is defined as (1) large number of subjects, (2) double-blind, independent assessment, (3) high follow-up rate (low dropout rate), and (3) Low protocol deviation (4) Clear random allocation method, etc.