Further evidence of the limited role of candidate genes in relation to infant-mother attachment outcomes

Attachment security and disorganization in infants of mothers with severe psychiatric disorder: Exploring the role of comorbid personality disorder

The aim of this preliminary study was to explore infant-mother attachment quality in a Dutch clinical sample of mothers with severe psychiatric disorder, with or without comorbid personality disorder. Thirty-two mothers were recruited through specialized secondary and tertiary outpatient clinics and mental health institutions. Maternal psychiatric and personality diagnoses were verified with structured clinical interviews during pregnancy. Maternal concurrent level of psychiatric symptoms was assessed by self-report and infant-mother attachment quality by observation in the Strange Situation Procedure at 14 months postpartum. In the full sample, almost half of the infants were classified as disorganized. All infants of mothers with a comorbid personality disorder were classified as either insecure or disorganized. Infants of mothers with a comorbid personality disorder had a significantly higher disorganization score than infants of mothers with a psychiatric disorder only. Continuous attachment security scores did not differ significantly between groups. In the full sample, continuous infant attachment security and disorganization score were not significantly correlated with the level of maternal concurrent psychiatric symptoms. Our exploratory findings suggest a specific link between maternal psychiatric and comorbid personality disorder and attachment disorganization. Moreover, chronicity of symptoms appears more relevant for attachment behaviors than the severity of concurrent psychiatric symptoms. Maternal personality disorder may have a strong formative impact on infant attachment security and disorganization, which warrants further research to inform clinical practice, in order to reduce the risk of intergenerational transmission of maternal psychopathology.

Developmental cascades from early childhood attachment security to adolescent level of personality functioning among high-risk youth

This study examines associations between early childhood attachment security and adolescent personality functioning in a high-risk sample within a developmental psychopathology framework. Data from 2,268 children (1165 male; 1103 female) and caregivers participating in Future of Families and Child Well-Being Study (FFCWS) were used to examine (1) effects of genetic polymorphisms of the serotonin transporter (5-HTTLPR) and dopamine D4 receptor (DRD4) genes and adverse childhood experiences (ACEs) on attachment security and emotional and behavioral dysregulation in early childhood and (2) longitudinal associations and transactional relationships among attachment security, dysregulation, negative parenting attitudes and behaviors, social competence, and adolescent personality functioning. Results revealed that ACEs predicted attachment security over and above sex or the genetic risk, and gene × environment interactions did not increment prediction. Results of cascade models showed that greater early childhood attachment security predicted higher adolescent level of personality functioning via pathways through intermediary variables. Limitations and future research directions are discussed.

Neurobiology of Disorganized Attachment: A Review of Primary Studies on Human Beings

This article describes and analyzes various aspects related to the neurobiology of disorganized attachment (DA), which is associated with personality, eating, affective, dissociative, and addictive disorders. We included primary studies in humans, published in PubMed from 2000 to 2022. Eight genetic and one epigenetic study were considered. Three molecular studies describe possible roles of oxytocin and cortisol, seven neurophysiological studies investigated functional correlates, and five morphological studies describe anatomical changes. Findings in candidate genes involved in dopaminergic, serotonergic, and oxytonergic systems have not been able to be replicated in large-scale human studies. Alterations in the functioning of cortisol and oxytocin are preliminary. Neurophysiological studies show changes in subcortical structures (mainly in the hippocampus) and occipital, temporal, parietal, and insular cortices. Since there is a lack of robust evidence on the neurobiology of DA in humans, the possible inferences of these studies are preliminary, which restricts their translation to clinical parameters.

Roles of the Oxytocin Receptor (OXTR) in Human Diseases

The oxytocin receptor (OXTR), encoded by the OXTR gene, is responsible for the signal transduction after binding its ligand, oxytocin. Although this signaling is primarily involved in controlling maternal behavior, it was demonstrated that OXTR also plays a role in the development of the nervous system. Therefore, it is not a surprise that both the ligand and the receptor are involved in the modulation of behaviors, especially those related to sexual, social, and stress-induced activities. As in the case of every regulatory system, any disturbances in the structures or functions of oxytocin and OXTR may lead to the development or modulation of various diseases related to the regulated functions, which in this case include either mental problems (autism, depression, schizophrenia, obsessive-compulsive disorders) or those related to the functioning of reproductive organs (endometriosis, uterine adenomyosis, premature birth). Nevertheless, OXTR abnormalities are also connected to other diseases, including cancer, cardiac disorders, osteoporosis, and obesity. Recent reports indicated that the changes in the levels of OXTR and the formation of its aggregates may influence the course of some inherited metabolic diseases, such as mucopolysaccharidoses. In this review, the involvement of OXTR dysfunctions and OXTR polymorphisms in the development of different diseases is summarized and discussed. The analysis of published results led us to suggest that changes in OXTR expression and OXTR abundance and activity are not specific to individual diseases, but rather they influence processes (mostly related to behavioral changes) that might modulate the course of various disorders. Moreover, a possible explanation of the discrepancies in the published results of effects of the OXTR gene polymorphisms and methylation on different diseases is proposed.

Oxytocin receptor gene (OXTR) polymorphisms and social, emotional and behavioral functioning in children and adolescents: a systematic narrative review

This study systematically reviewed available evidence regarding associations between polymorphisms of the oxytocin receptor (OXTR) gene and socio-emotional and behavioral functioning in children and adolescents. The search yielded 69 articles, which were grouped into nine categories: depression, anxiety, and internalizing symptoms, alcohol abuse, borderline personality disorder, conduct disorder symptoms or diagnosis, autism spectrum disorder, Attention deficit hyperactivity disorder, early childhood attachment and behavior, pro-social skills, and resilience. Direct and/or gene x environment interactions were identified in over half of the studies. ASD and conduct disorder (including callous unemotional traits) were the diagnoses that were most studied and for which there was the strongest evidence of direct links with OXTR polymorphisms. In most studies identifying gene x environment interactions, the candidate OXTR polymorphism was rs53576. Results suggest that OXTR polymorphisms are associated with social, emotional or behavioural functioning in children and adolescents. The mixed findings do, however, highlight the need for further research.

The Effects of At-Birth Adoption on Atypical Behavior and Anxiety: A Nonhuman Primate Model

OBJECTIVE

Adopted children tend to show an increased risk for a variety of psychopathological outcomes, even when adoption occurs at birth, which some suggest is a result of nonrandom assignment of adoptees and parents. This study uses a nonhuman primate model, in which adoptions were randomly assigned, to investigate the behavioral and physiological outcomes associated with at-birth adoption.

METHOD

Immediately following birth, rhesus monkey infants were randomly assigned to be reared by either their biological mother (n = 113) or by an unrelated, lactating, adoptive mother (n = 34). At 6 months of age, infant behavior and physiology were assessed during a stressful series of mother-infant separations. Four years later, stress-related behaviors were measured following confrontation by an unfamiliar intruder, an ecologically meaningful stressor.

RESULTS

When compared to infants reared by their biological mothers, adopted infants exhibited more behavioral withdrawal and higher plasma adrenocorticotropic hormone (ACTH) concentrations in response to separation. These behavioral differences persisted 4 years later during a stressful intruder challenge, with adoptees exhibiting more behavioral withdrawal, stereotypies, and impulsive approaches of the potentially aggressive intruder.

CONCLUSION

Compared to infants reared by their biological mothers, adopted infants exhibited more behavioral inhibition, impulsivity, and higher ACTH concentrations, even when subjects were randomly assigned to be adopted or to remain with their biological mother. To the extent that these findings generalize to humans, they suggest that the overall risk for psychopathology in adopted individuals persists even after random assignment to adoption conditions.

The OXTR polymorphisms are not associated with attachment dimensions: A three-approach study

Inspired by the roles of oxytocin in social behaviors, scientists have devoted considerable efforts to examine the association between the oxytocin receptor gene (OXTR) and human attachment, a personality of seek and receiving comfort from intimate figures. However, there are still a lot of controversies on the association. To clarify the relationship, this research integrated three studies: (1) A cross-sectional study indicated that the OXTR polymorphisms (i.e., rs53576 and rs2254298) were not significantly associated with attachment dimensions in a college student sample (N = 1193); (2) A three-wave study showed that the polymorphisms were not associated with the individual differences and changes of attachment dimensions in a freshmen sample (N = 657); and (3) Meta-analysis indicated that attachment dimensions were not associated with the polymorphisms of rs53576 (Anxiety: 14 samples, N = 5053; Avoidance: ten samples, N = 4273) and rs2254298 (Anxiety: ten samples, N = 3670; Avoidance: ten samples, N = 3698). Taken together, these findings provide strong evidence that the OXTR polymorphisms are not related to attachment dimensions.

Socioemotional Mechanisms of Children's Differential Response to the Effects of Maternal Sensitivity on Child Adjustment

OBJECTIVE

Children differ in the extent to which they reap the benefits of maternal sensitive care or suffer the adverse consequences of insensitive care, and these differences can be accounted for by biological characteristics. However, how susceptible children adapt to maternal sensitivity in ways that either maximize positive development or lead to maladjustment has yet to be determined. Here, we propose a novel model of socioemotional mechanisms by which the joint influences of maternal sensitivity and child biological characteristics influence child adjustment.

DESIGN

We propose a theoretical model, in which children's vagal functioning and polymorphisms in serotonin transporter (5-HTTLPR) and dopamine receptor D4 (DRD4) genes confer susceptibility to the effects of maternal sensitivity on internalizing, externalizing, prosocial and moral behavior via changes in interpersonal strategies for emotion regulation, the threat response system, and empathy.

RESULTS

Theoretical and empirical support for the proposed mechanisms are provided.

CONCLUSIONS

The proposed mechanistic model of susceptibility to maternal sensitivity offers a novel framework of for whom and how children are affected by early maternal care, highlighting multiple reciprocal, interacting influences across genes, physiology, behavior, and the environment.

Disentangling genes, attachment, and environment: A systematic review of the developmental psychopathology literature on gene-environment interactions and attachment

The role of genetics in relation to attachment is of continued interest to developmental psychology. Recent research has attempted to disentangle genetic main effects, environmental effects, and gene and environment (G × E) interactions in the development of attachment security/insecurity and disorganization. We systematically reviewed associations between gene markers and attachment, including G × E interactions, identifying 27 eligible studies. Inconsistent results emerged for associations between both gene effects and G × E interactions on attachment organization. Where G × E interactions used attachment as the environmental factor in the interaction, we observed more consistent results for differential susceptibility of G × E interactions on offspring behavior. Small sample size and heterogeneity in measurement of environmental factors impacted on comparability of studies. From these results, we propose that the future of research into the role of genetic effects in attachment lies in further exploration of G × E interactions, particularly where attachment acts as an environmental factor impacting on other child developmental outcomes emerging from the caregiving environment, consistent with differential susceptibility approaches to developmental psychopathology. In addition, from a methodological perspective, establishing the role of gene markers in such models will require a shift toward contemporary genomics, including genome-wide analysis (including novel genes and chromosomal loci), and epigenetic individual variations.

Genes and environment in attachment

In the last two decades, there has been increasing research interest in disentangling the contribution of genetic and environmental factors to individual differences in attachment, and in identifying the genes involved in shaping attachment. Twin studies suggest that as attachment changes during the course of development, genetic factors may play a progressively more important role, while shared environmental effects might decrease. However, most of this literature is limited by low power, measurement issues, and cross-sectional design. The findings of molecular genetic studies are, overall, inconclusive. The literature on main genetic effects and gene-by-environment interactions on attachment is filled with inconsistent and unreplicated findings. Also, most studies are underpowered. Challenges for future research are to identify the unshared environmental mechanisms involved in shaping attachment, and to better elucidate the genes involved and their interaction with the environment. Some pioneer studies suggested that the incorporation of epigenetic processes into G × E interaction models might represent a promising future way for investigating the complex, dynamic interplay between genes, environment, and attachment.

An initial investigation of neonatal neuroanatomy, caregiving, and levels of disorganized behavior

Attachment disorganization is a risk factor for difficulties in attention, social relationships, and mental health. Conceptually, attachment disorganization may indicate a breakdown in fear regulation resulting from repeated exposure to frightening maternal care. In addition, past research has examined the influence of stress-inducing contextual factors and/or child factors upon the development of disorganization. However, no past work has assessed whether infant neuroanatomy, important to stress regulation, moderates the association between maternal care and levels of disorganized behavior. Here, utilizing data from a subsample of 82 dyads taking part in the "Growing Up in Singapore towards Healthy Outcomes" (GUSTO) cohort, we assessed the prediction from maternal sensitive caregiving at 6 mo and levels of attachment disorganization at 1.5 y, as moderated by hippocampal and amygdala volume determined within the first 2 weeks of life. Results indicate a significant interaction between neonatal left hippocampal volume and maternal sensitivity upon levels of disorganized behavior. Although these results require substantiation in further research, if replicated, they may enable new strategies for the identification of processes important to child mental health and points for intervention. This is because neonatal neuroanatomy, as opposed to genetic variation and sociodemographic risk, may be more directly linked to stress responses within individuals.

Relations between early maternal sensitivity and toddler self-regulation: Exploring variation by oxytocin and dopamine D2 receptor genes

Gene-by-environment interactions between maternal sensitivity during infancy and child oxytocin receptor gene (OXTR rs53576) and D2 dopamine receptor gene (DRD2 TaqIA, rs1822497) genotypes were explored as predictors of toddlers' well-regulated behavioral and physiological responses to maternal compliance demands. Maternal sensitivity was assessed across a range of mother-child interactions when children were 6 months and 1 year of age (N = 186), and toddler self-regulatory responses were assessed through compliance and vagal withdrawal during a toy clean-up task when children were 2 years of age. Sensitivity-by-OXTR interactions suggested two diathesis-stress patterns, predicting compliance for the GG genotype group, and predicting physiological regulation for the AA/AG genotype group. A main effect for DRD2 genotype indicated that children with an A1 allele displayed less-compliant behavior in toddlerhood. These results suggest that genetic differences may contribute to variation both in risk for self-regulatory difficulties, and in relations between maternal sensitivity and children's responses to compliance demands at different levels of analysis.

Epigenetic modification of the oxytocin and glucocorticoid receptor genes is linked to attachment avoidance in young adults

Attachment in the context of intimate pair bonds is most frequently studied in terms of the universal strategy to draw near, or away, from significant others at moments of personal distress. However, important interindividual differences in the quality of attachment exist, usually captured through secure versus insecure - anxious and/or avoidant - attachment orientations. Since Bowlby's pioneering writings on the theory of attachment, it has been assumed that attachment orientations are influenced by both genetic and social factors - what we would today describe and measure as gene by environment interaction mediated by epigenetic DNA modification - but research in humans on this topic remains extremely limited. We for the first time examined relations between intra-individual differences in attachment and epigenetic modification of the oxytocin receptor (OXTR) and glucocorticoid receptor (NR3C1) gene promoter in 109 young adult human participants. Our results revealed that attachment avoidance was significantly and specifically associated with increased OXTR and NR3C1 promoter methylation. These findings offer first tentative clues on the possible etiology of attachment avoidance in humans by showing epigenetic modification in genes related to both social stress regulation and HPA axis functioning.

Testing an Attachment-Based Parenting Intervention-VIPP-FC/A in Adoptive Families with Post-institutionalized Children: Do Maternal Sensitivity and Genetic Markers Count?

This study investigated the effectiveness of a newly integrated version of an intervention targeting adoptive mothers' positive parenting for promoting children's emotional availability, by testing the moderating role of both two maternal genetic polymorphisms (i.e., 5HTTLPR and DRD4-VNTR) and emotional availability-EA on intervention outcomes. Mothers with their children (N = 80; Mage = 42.73 years, SD = 3.79; Mage = 33.18 months, SD = 16.83 months) participated in a RCT testing the Video-Feedback Intervention to Promote Positive Parenting and Sensitive Discipline-VIPP-FC/A effectiveness. Mixed effects regression models showed a significant improvement in mother-child EA for the VIPP-intervention vs. the dummy intervention condition, with a moderating role of maternal EA on children's outcomes. No significant moderating effect was found for the two genetic polymorphisms inquired. Children's and mother's outcomes obtained are discussed.