Epidemiology and Psychiatric Sciences

ABC of Methodology

Why it is important to include unpublished data in systematic reviews

C. Trespidia1, C. Barbuia1 and A. Cipriania1 c1

a1 Section of Psychiatry and Clinical Psychology, Department of Public Health and Community Medicine, University of Verona, Piazzale L.A. Scuro, 10-37134 Verona, Italy

It is known that studies with statistically significant results have a higher probability to be published (publication bias). Therefore, studies with no statistically significant differences (or not favoring the investigational drug) may not be found in commonly accessed databases and remain unpublished. Moreover, unpublished data may also refer to information that are not included in study reports published in scientific journals but that may be important to estimate study outcomes. Retrieving unpublished evidence represents a compelling challenge for researchers, and in the present paper we explore how to do it.

(Received December 09 2010)

(Revised December 20 2010)

(Accepted December 20 2010)

(Online publication April 01 2011)

Correspondence

c1 Address for correspondence: Andrea Cipriani, Section of Psychiatry and Clinical Psychology, Department of Public Health and Community Medicine, University of Verona, Piazzale L.A. Scuro, 10-37134 Verona, Italy (Email: andrea.cipriani@univr.it)

Footnotes

This is a section of Epidemiologia e Psichiatria Sociale, which regularly covers methodological aspects related to the design, conduct, reporting and interpretation of clinical and epidemiological studies. We hope that these editorials will help develop a more critical attitude towards research findings published in the international literature and, additionally, will help promote the implementation of original research projects with higher standards in terms of design, conduct and reporting.

Corrado Barbui, Section Editor and Michele Tansella, Editor EPS