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Citation bias and selective focus on positive findings in the literature on the serotonin transporter gene (5-HTTLPR), life stress and depression

Published online by Cambridge University Press:  12 August 2016

Y. A. de Vries ,
A. M. Roest ,
M. Franzen ,
M. R. Munafò  and
J. A. Bastiaansen
Y. A. de Vries*
Affiliation:
Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
A. M. Roest
Affiliation:
Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
M. Franzen
Affiliation:
Department of Psychology, University of Groningen, Groningen, The Netherlands
M. R. Munafò
Affiliation:
MRC Integrative Epidemiology Unit (IEU) at the University of Bristol, Bristol, UK UK Centre for Tobacco and Alcohol Studies, School of Experimental Psychology, University of Bristol, Bristol, UK
J. A. Bastiaansen
Affiliation:
Department of Psychiatry, Interdisciplinary Center Psychopathology and Emotion Regulation, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
*
*Address for correspondence: Y. A. de Vries, M.Sc., Department of Psychiatry, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands. (Email: y.a.de.vries@umcg.nl)
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Abstract

Background

Caspi et al.'s 2003 report that 5-HTTLPR genotype moderates the influence of life stress on depression has been highly influential but remains contentious. We examined whether the evidence base for the 5-HTTLPR–stress interaction has been distorted by citation bias and a selective focus on positive findings.

Method

A total of 73 primary studies were coded for study outcomes and focus on positive findings in the abstract. Citation rates were compared between studies with positive and negative results, both within this network of primary studies and in Web of Science. In addition, the impact of focus on citation rates was examined.

Results

In all, 24 (33%) studies were coded as positive, but these received 48% of within-network and 68% of Web of Science citations. The 38 (52%) negative studies received 42 and 23% of citations, respectively, while the 11 (15%) unclear studies received 10 and 9%. Of the negative studies, the 16 studies without a positive focus (42%) received 47% of within-network citations and 32% of Web of Science citations, while the 13 (34%) studies with a positive focus received 39 and 51%, respectively, and the nine (24%) studies with a partially positive focus received 14 and 17%.

Conclusions

Negative studies received fewer citations than positive studies. Furthermore, over half of the negative studies had a (partially) positive focus, and Web of Science citation rates were higher for these studies. Thus, discussion of the 5-HTTLPR–stress interaction is more positive than warranted. This study exemplifies how evidence-base-distorting mechanisms undermine the authenticity of research findings.

Keywords

Citation biasdepression5-HTTLPRstress
Type
Original Articles
Information
Psychological Medicine , Volume 46 , Issue 14 , October 2016 , pp. 2971 - 2979
Copyright
Copyright © Cambridge University Press 2016 

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