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

Ymkje Anna de Vries, Annelieke M. Roest, Minita Franzen, Marcus Munafo, Jojanneke A Bastiaansen

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)
399 Downloads (Pure)


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.

Methods: Seventy-three 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: Twenty-four (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 9 (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.
Original languageEnglish
Pages (from-to)2971-2979
Number of pages9
JournalPsychological Medicine
Issue number14
Early online date12 Aug 2016
Publication statusPublished - Oct 2016

Structured keywords

  • Brain and Behaviour
  • Tobacco and Alcohol


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