ADDRESSING PUBLICATION BIAS

It is important to note that while some degree of bias is nearly inevitable in studies, understanding these biases and their manifestations in study designs is crucial to mitigate their impact on the conclusions of a meta-analysis. Publication bias can distort meta-analyses by amplifying effects requiring identification and correction. To mitigate the influence of publication and reporting bias, as well as questionable research practices (QRPs), various techniques can be employed in meta-analyses. These approaches encompass methods for study search as well as statistical methods:

1. Study search: If publication bias exists, this step is crucial because it means that a search of the published literature may yield data that is only partially representative of all the evidence. We can counteract this by searching for grey literature, including dissertations, preprints, government reports, or conference proceedings. Fortunately, pre-registration is also becoming more common in many disciplines. This makes it possible to search study registries for studies with unpublished data and ask the authors if they can provide data that has not been made public (yet). Grey literature search can be tedious and frustrating, but it is worthwhile. One large study has found that including grey and unpublished literature can help avoid overestimating the true effects.
2. Statistical methods: Statistical procedures can also examine the presence of publication. It is important to note that none of these methods can directly pinpoint publication bias. However, they can scrutinise particular properties of the data that might serve as potential indicators of its presence. Some methods can also quantify the true overall effect when correcting for publication bias.