title: Evolution of Cooperation Patterns in Psoriasis Research: Co-Authorship Network Analysis of Papers in Medline (1942-2013).
abstract: BACKGROUND
  Although researchers have worked in collaboration since the origins of modern science and the publication of the first scientific journals in the eighteenth century, this phenomenon has acquired exceptional importance in the last several decades. Since the mid-twentieth century, new knowledge has been generated from within an ever-growing network of investigators, working cooperatively in research groups across countries and institutions. Cooperation is a crucial determinant of academic success.
  
  
  OBJECTIVE
  The aim of the present paper is to analyze the evolution of scientific collaboration at the micro level, with regard to the scientific production generated on psoriasis research.
  
  
  METHODS
  A bibliographic search in the Medline database containing the MeSH terms "psoriasis" or "psoriatic arthritis" was carried out. The search results were limited to articles, reviews and letters. After identifying the co-authorships of documents on psoriasis indexed in the Medline database (1942-2013), various bibliometric indicators were obtained, including the average number of authors per document and degree of multi-authorship over time. In addition, we performed a network analysis to study the evolution of certain features of the co-authorship network as a whole: average degree, size of the largest component, clustering coefficient, density and average distance. We also analyzed the evolution of the giant component to characterize the changing research patterns in the field, and we calculated social network indicators for the nodes, namely betweenness and closeness.
  
  
  RESULTS
  The main active research clusters in the area were identified, along with their authors of reference. Our analysis of 28,670 documents sheds light on different aspects related to the evolution of scientific collaboration in the field, including the progressive increase in the mean number of co-authors (which stood at 5.17 in the 2004-2013 decade), and the rise in multi-authored papers signed by many different authors (in the same decade, 25.77% of the documents had between 6 and 9 co-authors, and 10.28% had 10 or more). With regard to the network indicators, the average degree gradually increased up to 10.97 in the study period. The percentage of authors pertaining to the largest component also rose to 73.02% of the authors. The clustering coefficient, on the other hand, remained stable throughout the entire 70-year period, with values hovering around 0.9. Finally, the average distance peaked in the decades 1974-1983 (8.29) and 1984-2003 (8.12) then fell over the next two decades, down to 5.25 in 2004-2013. The construction of the co-authorship network (threshold of collaboration ≥ 10 co-authored works) revealed a giant component of 161 researchers, containing 6 highly cohesive sub-components.
  
  
  CONCLUSIONS
  Our study reveals the existence of a growing research community in which collaboration is increasingly important. We can highlight an essential feature associated with scientific collaboration: multi-authored papers, with growing numbers of collaborators contributing to them, are becoming more and more common, therefore the formation of research groups of increasing depth (specialization) and breadth (multidisciplinarity) is now a cornerstone of research success.
authors.affiliation: Department of History of Science and Documentation, Universitat de València, Valencia, Spain.
authors.forename: Gregorio
authors.initials: G
authors.lastname: González-Alcaide
authors.affiliation: Korea Institute of Science and Technology Information (KISTI), Deajeon, South Korea.
authors.forename: Jinseo
authors.initials: J
authors.lastname: Park
authors.affiliation: Instituto Nacional de Salud, Lima, Perú
authors.forename: Charles
authors.initials: C
authors.lastname: Huamaní
authors.affiliation: Department of Dermatology, Hospital General Universitario de Alicante, Alicante, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Belinchón
authors.affiliation: Department of Medicine, Universidad Miguel Hernández de Elche, Alicante, Spain.|Department of Internal Medicine, Hospital General Universitario de Alicante, Alicante, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Ramos
mesh_terms: D001319:Authorship; D015706:Bibliometrics; D035843:Biomedical Research; D003299:Cooperative Behavior; D006801:Humans; D033181:Information Dissemination; D016239:MEDLINE; D010506:Periodicals as Topic / Q000941:ethics; D011565:Psoriasis / Q000628:therapy*; D012108:Research Personnel / Q000941:ethics* / Q000523:psychology; D060756:Social Networking; D000078329:Workforce