OXTR rs53576 genotype and gender predict trait gratitude

Abstract

Dispositional gratitude was investigated in 190 (96 M, 94 F) participants with saliva samples genotyped for the oxytocin receptor gene single nucleotide polymorphism (SNP) rs53576 (112 A-carriers, 78 GGs). Trait gratitude was measured using the Gratitude Questionnaire-6 (GQ-6), and trait empathy was assessed with the Interpersonal Reactivity Index (IRI Perspective Taking and Empathic Concern). Due to non-normal distributions of the GQ-6 by SNP group and by gender, non-parametric analyses using simulations and bootstrap 95% CIs were conducted. Results show main effects of SNP group (with GGs scoring higher than A-carriers) and gender (with females scoring higher than males) on trait gratitude. Given the associations of both the OXTR SNP rs53576 and gender with empathy, and the prosocial associations of trait empathy and gratitude, we tested an indirect effects model using PROCESS. Results showed that both SNP group and gender had an indirect effect on trait gratitude through trait empathy.

Keywords:

• Empathy
• gratitude
• gender
• oxytocin
• rs53576

Acknowledgements

We thank Samantha Moffat, Morgan Miller, Elizabeth Perkins, Chloe Werkema, Madeleine Ryan, Marina Milad, and Audrey Black for their active participation in data collection and analysis. The authors gratefully acknowledge Elliott Johnson for assistance in the genotyping work. We appreciate the assistance of Fallon Richie and Nicholas Pikaart with pilot-testing the protocol. This work was supported by a research grant from the Frost Research Center.

Notes

1. We determined the sample size and statistical power for gratitude data as follows. We aimed to have a total sample size of 200 (100 males and 100 females) to have a power of at least 0.8. A priori power calculations utilized an effect size of 0.11, which was reported by Li et al. (2015) in a study examining OXTR rs53576 genotype and sociality. Moreover, given that the present study was conducted in the Western Hemisphere, our projected sample size of 200 (100 participants for each gender) would allow for statistical comparison between individuals homozygous for the G allele and A-allele carriers (with much lower abundance in Western hemisphere cultures). As noted below, we collected a total of 202 participants, of which 11 did not have pure saliva, and one lacked gratitude data. Post-hoc power analyses were conducted; however, the SNP groups had different Ns. The observed power value for gratitude of 0.788 uses the sample size of 112 for both As and GGs, and the power of 0.631 uses 78 as the sample size of both As and GGs; in reality, the power is somewhere in between those two numbers with effect size 0.3299. For gender, power was between 0.943 and 0.954 with effect size 0.5066.

This sample was part of a study of 202 participants who answered additional questions about affective traits and states. Of the 202 participants, 11 participants did not have viable saliva samples: nine did not meet purity standards, and two vials were mislabeled with the same participant number. All others were able to be genotyped, yielding 26 AAs, 86 AGs, and 78 GGs. One person did not answer any trait gratitude questions. Thus, the analyzed sample had 190 participants. The sample GGs included 36 females and 42 males; AAs included 12 females and 14 males; AGs included 46 females and 40 males.