Oxytocin system polymorphisms rs237887 and rs2740210 variants increase the risk of depression in pregnant women with early abuse.

Prepartum depression is associated with early adversity, pregnancy complications, preterm delivery, postpartum depression, and long-term effects on child neurodevelopment. The oxytocin (OXT) system is affected by early adverse experiences and has been associated with depression. In the current study, we investigated risk factors for prenatal depressive symptoms, mainly the effects of early childhood and adolescence trauma, in combination with the presence of certain variants of polymorphisms of OXT and OXT receptor (OXTR) genes. We hypothesized that early childhood and adolescence trauma has higher negative effects in carriers of genetic variants of the OXT/OXTR system, increasing their risk for depression. Early in pregnancy (8-14 weeks), 141 pregnant women from a Uruguayan population were asked to provide DNA samples and complete questionnaires that assessed their experience of child abuse, depression symptoms, and other variables that included demographic information. Our results showed that 23.5% of pregnant women had depressive symptoms. Several OXT and OXTR genetic variants were associated with higher risk of prepartum depression only in those pregnant women who suffered emotional abuse during infancy or adolescence. Logistic regression (Nagelkerke's R2  = .33) revealed that women who suffered early abuse and were carriers of the variants CC of rs2740210 (OXT) or AA of rs237887 (OXTR) had significantly higher risk of experiencing depressive symptoms. Antecedents of psychiatric disorders also contributed to the risk of depression. We conclude that emotional abuse contributes to the risk of depression in different ways in women carrying different OXT and OXTR genetic variants. Early detection and closer follow-up of women with child abuse and certain OXT genetic variants, among other risk factors, could reduce the long-term impact of prepartum depression.

Variation in the density of oxytocin receptors in the brain as mechanism of adaptation to specific social and reproductive strategies.

Most species have predominant forms of social and reproductive behavior driven by many years of selection pressures and evolution. For example, rodent species can live in small or large groups, behave more tolerant or aggressively toward conspecifics (including newborns), and form or not bonds with other members of the group (including sexual partners). Any of those behavioral adaptations could result in good fitness for the species, but could also require compromises such as sharing resources, greater parental investment, increased risk of predation, etc. We propose that the oxytocin (OXT) system, among others neuroendocrine peptides, is at the basis of a neural mechanism that adapts and predisposes species to a particular social and reproductive form of living. In this review we will show evidence that the variability in the density of receptors for OXT (OXTR) in the nucleus accumbens (NAc) and the lateral septum (LS) predisposes species to adopt at least 4 different social and reproductive strategies in rodents. Large or medium size groups with lower conspecific spacing (preferred separation distance maintained by adult conspecifics), and high levels of promiscuity are characterized by low levels of OXTR in the NAc and LS (e.g. Ratus norvegicus, Ctenomys sociabilis, Scotinomys teguina, Cavia porcellus); small size groups with higher conspecific spacing and low levels of promiscuity are characterized by high OXTR in the NAc and the LS (e.g. Peromyscus californicus); large or medium groups with lower conspecific spacing and low levels of promiscuity characterized by high levels of OXTR in the NAc but low levels in the LS (e.g. Microtus ochrogaster, Heterocephalus glaber, Microtus kikuchii); and small or medium size groups with higher conspecific spacing and high levels of promiscuity characterized by low levels of OXTR in the NAc and high OXTR in the LS (e.g. Mus musculus, Ctenomys haigi, Peromyscus maniculatus, Microtus pennsylvanicus, Microtus montanus). Careful analysis of the distribution of OXTR, and other peptides receptors, in the brain can contribute to understand its function but also to predict reproductive and social strategies of species.