Systematic reviews in mental health have become useful tools for health professionals in view of the massive amount and heterogeneous nature of biomedical information available today. In order to determine the risk of bias in the studies evaluated and to avoid bias in generalizing conclusions from the reviews it is therefore important to use a very strict methodology in systematic reviews. One bias which may affect the generalization of results is publication bias, which is determined by the nature and direction of the study results. To control or minimize this type of bias, the authors of systematic reviews undertake comprehensive searches of medical databases and expand on the findings, often undertaking searches of grey literature (material which is not formally published). This paper attempts to show the consequences (and risk) of generalizing the implications of grey literature in the control of publication bias, as was proposed in a recent systematic work. By repeating the analyses for the same outcome from three different systematic reviews that included both published and grey literature our results showed that confusion between grey literature and publication bias may affect the results of a concrete meta-analysis.

This paper presents a systematic study of later Bronze Age practices at round barrows – features that are typically seen as emblematic of the Early Bronze Age in Britain. Examining the evidence from 87 excavated round barrows in the east of England, it adds subtlety and empirical detail to previous discussions about the changing role of funerary monuments over the course of the 2nd millennium bc. A wide variety of activities was undertaken at existing round barrows in the later Bronze Age. Burials were added, the monuments themselves were augmented and replicated, they were often actively built into land boundary systems, and settlements were located close to them. The findings not only attest to the continued (if shifting) significance of round barrows in the later Bronze Age, they also contribute substantially to wider debates about the character of life during this period in lowland Britain – the shifting relationship between ‘ritual’ and ‘everyday’ practices, and the processes by which mobile communities began to settle down. More broadly, this investigation adds to a growing body of work that explores the multi-temporal qualities of later prehistoric landscapes.

To trace the local extinction of the Eurasian otter Lutra lutra in Latium, central Italy, and examine the causes of the species’ disappearance, we reviewed and classified information from both the scientific and grey literature according to the reliability and geographical accuracy of the records. The temporal and spatial patterns of 160 records from 23 geographical subunits from 1832 to 2006 suggest that the species collapsed between 1960 and 1975; two different extinction patterns were revealed by a set of multivariate analyses. In northern Latium the species collapsed because of several independent local threats. In central and southern Latium the species collapsed because of catastrophic habitat alteration (land reclamation during the 1930s) that negatively affected the source population. After this event the species went extinct in hilly and mountainous areas, where several population sinks occurred. We presume that this latter process drove the remnant otter subpopulations to extinction in central Italy, emphasizing the role of an extinction vortex in causing the collapse of this metapopulation rather than the classical threats recognized for this species. The value of the grey literature for a posteriori historical analysis of local extinction dynamics is highlighted by this research.