Finding studies for inclusion in systematic reviews of interventions for injury prevention – the importance of grey and unpublished literature

The inclusion of unpublished and grey literature is essential for minimizing the potential effects of publication bias. It is well known that published studies can not be assumed to be an accurate representation of the whole evidence base, as studies that show statistically significant, “positive” results are more likely to be published than those that do not.1 Consequently, if systematic reviews are limited to published studies, they risk excluding vital evidence and yielding inaccurate results, which are likely to be biased to positive results.2 Previous research has indicated that meta-analyses that exclude grey literature can lead to exaggerated estimates of intervention effects.34 It is therefore considered essential that active and extensive searching for unpublished and grey literature is undertaken as part of the review process for all CIG reviews, although we feel this to be particularly important for reviews of injury prevention interventions. …