Objectives: Objective and indirect evidence was used to determine whether required author contribution forms were associated with a decrease in author counts in four major general medicine journals (British Medical Journal [BMJ], Journal of the American Medical Association [JAMA], Canadian Medical Association Journal [CMAJ], and the Lancet). The number of authors listed per article before and after the introduction of explicit author contribution requirements were counted and compared with that found for the New England Journal of Medicine (NEJM) that did not require such disclosure. The primary hypothesis was that author counts decreased more in the BMJ, CMAJ, JAMA, and the Lancet after introduction of the rules than they did in the NEJM.
Study design and setting: The number of authors listed per original research article published in the five general medical journals with the greatest 2004 Impact Factors in the first issue of each month in the years before and after introduction of required author contribution forms was compared.
Results: Introduction of the required author contribution forms by the four leading general medical journals did not result in a drop in the rate of increasing authors per article per year, or in the number of authors per article compared with the control. Overall, there was a trend of an increasing number of authors listed per article.
Conclusion: Based on the presented objective and indirect evidence, required author contribution forms were not associated with a decrease in author counts.