About the Authors
Division of Epidemiology and Public Health, University of Nottingham, Nottingham, United Kingdom
The authors have declared that no competing interests exist.
Conceived and designed the experiments: JW MJG. Performed the experiments: FH MJG. Analyzed the data: FH MJG. Contributed reagents/materials/analysis tools: JW MJG. Wrote the first draft of the manuscript: FH MJG. Contributed to the writing of the manuscript: FH JW MJG. ICMJE criteria for authorship read and met: FH JW MJG. Agree with manuscript results and conclusions: FH JW MJG. Carried out original literature search: FH. Made decsions over which papers to include in the review: FH JW MJG. This work was originally carried out as a medical student project by FH under the supervision of JW and MJG prior to the search strategy being updated in July 2011.