To test for the presence of “positive results bias” (i.e., whether studies with positive results were more likely to participate in our meta-analysis than those with negative or inconclusive results), we drew a funnel plot of the interaction beta coefficients and standard errors and conducted Begg and Egger tests for bias. The funnel plot was symmetrical, and the results for Begg and Egger tests were non-significant (p = 0.9 and p = 0.8, respectively), indicating that our results were not affected by positive results bias (Figure S1).
