Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta) model

Abstract

Studies show that maternal behaviors are mediated by the bivariate serotonin transporter (5-HTT) genotype, although the findings are mixed, with some studies showing that mothers with thesallele exhibit increased maternal sensitivity, while other studies show that mothers with thesallele show decreased maternal sensitivity. Nonhuman primate studies offer increased control over extraneous variables and may contribute to a better understanding of the effects of the5-HTTgenotype on maternal sensitivity. This study assesses the influence of5-HTTgenotype variation on maternal sensitivity in parenting in 125 rhesus macaque mothers(Macaca mulatta) during the first three-months of their infants’ lives, an age well before typical infants undergo weaning. Mothers were genotyped for the5-HTTgenotype and maternal behaviors were collected, including neglectfulness, sensitivity, and premature rejections during undisturbed social interactions. Results showed that mothers homozygous for thesallele rejected their infants the most and restrained their infants the least, an indication that mothers with thesallele are more likely to neglect their infants’ psychological and physical needs. These findings suggest that, at an age when an infant’s needs are based on warmth, security, and protection, mothers with ansallele exhibit less sensitive maternal behaviors. High rates of rejections and low rates of restraints are behaviors that typically characterize premature weaning and are inappropriate for their infant’s young age. This study is an important step in understanding the etiology of variability in maternal warmth and care, and further suggests that maternal5-HTTgenotype should be examined in studies assessing genetic influences on variation in maternal sensitivity, and ultimately, mother-infant attachment quality.