Given the presence of significant moderation by the 5-HTTLPR genotype at both stages of the model, we examined whether the mediational component of the model presented in figure 1 would function significantly differently for s-allele carriers compared to ll-allele homozygotes, resulting in moderated mediation. To examine whether the observed differences for “s” allele carriers and others were significant, we used the moderated-mediation model outlined by Preacher et al. (2007; Model 5, p. 194). Using a bootstrapping technique with 3, 000 replications, the results indicated that there was a significant difference between the indirect effect of SAAF on OXTR methylation for “LL” homozygotes (indirect effect = −.003, 95% CI [−.023, .004] NS), compared to the effect for respondents who carried at least one copy of the “s” 5-HTTLPR allele (indirect effect = −.033, 95% CI [−.109, −.001]). Accordingly, the pattern reflects moderated mediation, with significant mediation of SAAF effects on OXTR methylation only among “s” allele carriers.
