Figure 1.
Levels of evidence (part 1). To be used in conjunction with table 3 and figure 2. Note: studies including ≤250 participants or studies not providing sample size justifying a smaller sample size are considered ‘small’, studies including >250 participants are considered ‘large’. Findings are considered consistent if at least two thirds (66.6%) of the highest quality studies are reported to have significant results in the same direction.