title: Negative results and impact factor: a lesson from neonatology.
abstract: OBJECTIVE
  To test the hypothesis that articles with negative results are more likely than articles with positive results to be published in journals with lower impact factor.
  
  
  METHODS
  We selected all of the randomized, placebo-controlled trials conducted during the neonatal period between October 1, 1998, and October 1, 2003. Trials were classified as having positive results or negative results (significant or no significant difference, respectively). Only studies dealing with primary outcomes (efficacy) were included.
  
  
  METHODS
  The impact factor of each journal was determined, and the sample size for each study was noted.
  
  
  RESULTS
  There were 233 articles that fulfilled the inclusion criteria. There was a significant difference between the 2 groups in terms of impact factor (P = .03) but not sample size (P = .30). Impact factor correlated with both sample size and the type of study results (positive results vs negative results; P<.05).
  
  
  CONCLUSIONS
  Articles with negative results are more likely than articles with positive results to be published in journals with lower impact factor.
authors.affiliation: Department of Neonatology, Lis Maternity Hospital, Tel Aviv Sourasky Medical Center, 6 Weitzman Street, Tel Aviv, Israel 64239.
authors.forename: Yoav
authors.initials: Y
authors.lastname: Littner
authors.forename: Francis B
authors.initials: FB
authors.lastname: Mimouni
authors.forename: Shaul
authors.initials: S
authors.lastname: Dollberg
authors.forename: Dror
authors.initials: D
authors.lastname: Mandel
mesh_terms: D015706:Bibliometrics; D006801:Humans; D007231:Infant, Newborn; D009359:Neonatology / Q000379:methods / Q000706:statistics & numerical data; D010506:Periodicals as Topic; D017594:Publication Bias; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D016896:Treatment Outcome