An emerging trend of equal authorship credit in major public health journals.

BACKGROUND: This study aimed to identify the longitudinal trends and characteristics of the practice of explicitly giving equal credit to multiple authors of publications in public health journals. Manual searches were conducted to identify original research articles, published in five public health journals with the highest IFs according to the "2012 JCR Science Edition" between January 1, 2004 and December 31, 2013, which awarded equal credit to multiple authors (Epidemiologic Reviews, Environmental Health Perspectives, the International Journal of Epidemiology, Epidemiology, and the Annual Review of Public Health). The Instructions to Authors in the five journals were also examined with regard to information about giving equal credit to multiple authors.

FINDINGS: Statistically significant differences were noted in the annual prevalence in Environmental Health Perspectives, International Journal of Epidemiology, and Epidemiology (r = 0.753, P = 0.012; r = 0.894, P = 0.000; r = 0.522, P = 0.122, respectively). The first two authors listed in the by-line received equal credit in the majority of articles, but this practice was also extended to authors in nearly every position on the by-line in some publications. The authors given equal credit in articles appearing in Environmental Health Perspectives, International Journal of Epidemiology, and Epidemiology were primarily from European and North American countries. Finally, none of the journals provided specific guidance regarding this practice in their Instructions to Authors.

CONCLUSIONS: An emerging trend of giving equal credit to multiple authors is observed in the public health journals. This practice should be better addressed in the guidance provided by journals to authors.