The quality of reporting of observational studies is an important issue [5
]. We found inappropriate use of causal language in the abstracts or titles of almost one third of human observational obesity or nutrition related study reports in four major obesity and nutrition journals. This is troubling because it misleads readers, particularly those who only peruse titles and abstracts. This may be especially true for less scientifically trained readers including reporters in the mass media who often have little scientific training and often describe themselves as having difficulty with key tasks involved in scientific reporting [6
]. Only a small proportion of articles included a disclaimer or statement of study limitations further increasing the risk of readers misapprehending the importance of the findings. While observational studies can contribute to the evidence supporting an accurate inference of causation, it requires understanding of design, analysis and statistical interpretation to determine whether a single observational study was designed, analyzed and executed sufficiently well to warrant an inference of causation.
Notably, we found that source of funding was not a determinant of the inappropriate use of causal language. In this one aspect then, in contrast to implications in the literature [8
], yet consistent with other recent findings [9
], these results suggest that industry-funded research is not necessarily reported any less accurately than is non-industry-funded research. However, only a relatively small proportion of observational studies in this area were funded by industry, leaving us with only 42 such studies to use in this comparison, a limitation of our study which lacked the power to determine a statistically significant difference. There are two other limitations to our analyses. Whereas we examined the title and the abstract for use of causal language in only four journals, we did select the four highest ranked by ISI's 2007 impact factor score. Our analysis was limited to the fields of obesity and nutrition; results might be different in other fields.
Given the limitations, the implications of our findings are severalfold. First, readers should be aware that the fact that statements implying causation can be found in the abstracts of peer-reviewed papers or quoted in secondary sources citing those papers does not necessarily imply that conclusions of causation are warranted but that readers have to carefully examine study designs themselves. Second, the fact that the rates varied so much by journal suggests that editorial and/or authorship practices may vary substantially among journals, leaving some with more opportunity for improvement. Third, our results can be seen as setting a benchmark of practices in 2006. Having established a protocol, it should not be difficult for editorial staff to collect such information on an ongoing basis as a way of assessing the rigor of their own editorial practices and monitoring for improvements over time.