Testing and adjusting for publication bias

How can the scientific literature provide unbiased conclusions if it repres ents a biased sample of available studies? Publication bias refers to pheno mena arising from bias in submitting, reviewing, accepting and publishing s cientific results. Direct and indirect methods for investigating publicatio n bias are now readily available, but indirect methods are generally open t o alternative interpretations. Publication bias distorts attempts to review a scientific field quantitatively if the likelihood of locating completed studies depends on the strength or direction of the findings of quantitativ e studies. It is the responsibility of researchers, reviewers and editors t o address issues of bias to ensure the existence of an unbiased literature.