Serotonin transporter allelic variation in mothers predicts maternal sensitivity, behavior and attitudes toward 6-month-old infants

Maternal behavior in the new mother is a multidimensional set of responses to infant cues that are influenced by the mother's early life experiences. In this study, we wanted to test if mothers' early life experiences and mothers' genotype have interactive effects on maternal behaviors and attitudes, something which has not been previously explored. In a sample of 204 mothers, we assessed maternal genotype at the serotonin transporter-linked polymorphic region (5-HTTLPR) and an adjacent upstream polymorphism (rs25531), together giving rise to three alleles: short (S), L(G) and L(A). Controlling for maternal age and parity, we showed that this genotype can predict differences in maternal sensitivity at 6 months postpartum: mothers with an S (or the functionally similar L(G)) allele were more sensitive than mothers who lacked the allele during a 30-min recorded mother-infant interaction (F (4,140) = 3.43; P = 0.01). Furthermore, we found highly significant gene-environment interactions in association with maternal behavior, such that mothers with no S or L(G) alleles oriented away more frequently from their babies if they also reported more negative early care quality (F (5,138) = 3.28; P = 0.008). Finally, we found significant gene-environment associations with maternal attitudes; mothers with the S allele and with greater early care quality scored higher on ratings of their perceived attachment to their baby (F (5,125) = 3.27; P = 0.008). The regression results show significant interactions between the reported quality of care mothers received from their own parents and genotype on both their frequency of orienting away from the infant during the interaction (F(5, 138) = 3.28; P = 0.008, Fig. 1a) and their perceived attachment feelings to the infant (F(5, 125) = 3.27; P = 0.008, Fig. 1b); however the direction of the effects for these two outcome measures were different from one another. With increasing care quality, mothers with the L(A)L(A) genotype (no S or L(G) allele) oriented away less frequently, while S or L(G) allele carriers showed no significant change. In contrast, with increasing early care quality. L(A)L(A) (no S or L(G) allele) mothers scored lower on perceived attachment to their infants, whereas S or L(G) allele carrying mothers scored higher. [corrected].     

Behavioral and adrenocortical responses of rhesus macaque mothers to infant separation in an unfamiliar environment

The behavioral and adrenocortical responses of rhesus macaque mothers to a series of four consecutive 4-day separations from their 5-month old infants in an unfamiliar environment were examined. A biphasic behavioral response to separation was observed, with passive behavior, locomotion, and vocalization highest on Day 1 of separation, and self-directed behaviors and environmental exploration peaking during Days 2–4. Stereotyped locomotion increased, and passive behavior decreased, across successive weeks of separation. The rhesus mothers exhibited substantial cortisol elevations one and two hours postseparation, with cortisol decreasing on the fourth day of separation. The cortisol response was strongest during the first week of separation, but robust elevations occurred in response to repeated separations. No signs of behavioral depression were observed. The results indicate that infant separation combined with removal to a novel environment can be a potent stressor for rhesus macaque mothers.