The aim of this study was to investigate citation bias in the literature on the serotonin-transporter-linked polymorphic region (5-HTTLPR), life stress, and amygdala activation. We included 73 studies from a recent meta-analysis by Sharpley et al. (2014).

Coding was done in duplicate by two independent raters. Study outcome was coded as positive, negative, or unclear. We coded a study outcome as unclear if we could not determine whether the 5-HTTLPR x stress interaction was significant, for instance because only the p-value associated with a three-way interaction (e.g., 5-HTTLPR x stress x gender) was presented. Study outcome was coded as positive if the extracted p-value was <0.05, provided that the interaction was in the expected direction (i.e., S allele associated with increased depression), and as negative otherwise. 

Abstracts were also coded in duplicate by two independent raters. Abstracts were coded as positive if a claim was made that the results supported the existence and/or importance of the 5-HTTLPR x stress interaction. Abstracts were coded as partially supportive if a positive claim was made that was not directly related to the 5-HTTLPR x stress interaction (e.g., positive findings for a three-way interaction) or if the abstract mentioned findings for multiple outcomes or stressors and not all were positive. Abstracts that did not make a positive claim or that made an explicitly negative claim were coded as negative. 

For each study, we counted by which of the other included studies it was cited in order to obtain the number of within-network citations. We also looked up the number of citations in Web of Science (date of search: October 2015). To generate two independent outcomes, we pruned the within-network citations from the Web of Science citations. 

The citation grid data sheet contains all data on citations within the network. The summary data sheet contains data on Web of Science citations and the summarized within-network citations.

The deposit includes the following files:

2016.04.14 5-HTTLPR GxE Citation Bias Grid Data Dictionary
2016.04.14 5-HTTLPR GxE Citation Bias Grid Data Sheet
2016.04.14 5-HTTLPR GxE Citation Bias Summary Data Dictionary
2016.04.14 5-HTTLPR GxE Citation Bias Summary Data Sheet
2016.04.14 5-HTTLPR GxE Citation Bias Study Description

The data files and variable key can be opened in Excel or SPSS software.

Sharpley CF, Palanisamy SKA, Glyde NS, Dillingham PW, Agnew LL (2014). An update on the interaction between the serotonin transporter promoter variant (5-HTTLPR), stress and depression, plus an exploration of non-confirming findings. Behavioural Brain Research, 273, 89 - 105.