Spin is defined as reporting practices that distort the interpretation of results and mislead readers to view the results in a more favourable light.

A research report usually starts with an introduction explaining why an investigation is performed and motivating the research question’s operational aim. The report then presents the patients, animals or cells that provide observations to be analysed and explains how the data are collected and analysed. Further sections of the report present the results of the evaluations and discuss the strengths and weaknesses of the investigation. The author interprets the results from the statistical analysis and accounts for the limitations imposed on the findings by the study design, data collection, and statistical methodology. A conclusion, based on the findings’ empirical support, finalises the report.

Ideally, the observed data and the statistical methods can answer the research question, the author's conclusions are consistent with the observed data, and no unsubstantiated claims are made. In practice, however, many reports have no unambiguous aim, the author’s conclusion is merely a summary of the analysis results, and the validity of the findings is unclear.

Some of these shortcomings probably reflect mistakes that can be explained by insufficient education and experience. However, many errors of both omission and commission have a tendency to exaggerate the importance of the presented findings as well as their empirical support. In addition, deliberate spin is a more common phenomenon than could be expected.

One systematic review shows, for example, that spin occurred in about half of all press releases from randomised trials (Yavchitz et al. Misrepresentation of Randomized Controlled Trials in Press Releases and News Coverage: A Cohort Study. PLoS Med 2012;9:e1001308.) and another systematic review (Chiu et al. ‘Spin’ in published biomedical literature: A methodological systematic review. PLoS Biol 2017;15:e2002173) did not find any difference in spin prevalence between different types of studies.