Oxytocin receptor gene (OXTR) in relation to loneliness in adolescence: interactions with sex, parental support, and DRD2 and 5-HTTLPR genotypes

The Effect of Peer Relationships on Adolescent Loneliness: The Role of Psychological Resilience and the OXTR Gene

Background

Based on the gene-environment interaction paradigm, this study explored the effect of peer relationships on adolescent loneliness and the role of psychological resilience and the oxytocin receptor gene (OXTR).

Methods

A survey was conducted in a sample of 619 adolescents, and their oral cells were collected for DNA extraction and genotyping.

Results

The results showed that (1) both peer relationships and psychological resilience significantly affected adolescent loneliness; (2) psychological resilience partially mediated the relationship between peer relationships and loneliness in adolescents; (3) OXTR gene rs53576 polymorphism moderated both the first and second half of the indirect pathway of the mediation model. Specifically, carriers of the rs53576 polymorphism A/A genotype showed a significantly enhanced effect of peer relationships on adolescent psychological resilience, while carriers of the rs53576 polymorphism G/G genotype showed a significantly enhanced effect of psychological resilience on adolescent loneliness.

Conclusion

These findings helped elucidate the developmental mechanisms of adolescent loneliness in terms of peer relationships, psychological resilience, and OXTR gene polymorphisms.

Potential Mechanism Linking Peer Relationships and Adolescent Prosocial Behavior: Mediation of Cognitive Empathy and Moderations of OXTR and DRD2

Peers are important socializers of adolescent prosocial behavior. Still, the proximal cognitive and emotional process underlying this link and the sources of individual differences in sensitivity to peer influence have yet to be explored. Utilizing the gene-gene-environment (G × G × E) approach and multi-informant measurement, this study investigated how peer relationships operate to influence adolescent prosocial behavior by examining the mediating role of cognitive and emotional empathy, and the moderating role of the OXTR and DRD2 genes. The study utilized longitudinal data from a community sample of Chinese adolescents (N = 1080, Mage = 13.32 years at T1). Results showed that cognitive empathy rather than emotional empathy mediated the link between peer acceptance/rejection and prosocial behavior. Furthermore, the association among peer acceptance, cognitive empathy, and prosocial behavior was moderated by OXTR and DRD2. Specifically, adolescents with the combinations of AA/AA or G/G genotypes of OXTR/DRD2 benefited more from peer acceptance compared to their counterparts carrying other combined genotypes. The findings highlight cognitive empathy as a proximal process linking peer interaction to prosocial behavior and lend support to the interaction between oxytocinergic and dopaminergic systems on environmental sensitivity.

Neurogenetics and Epigenetics of Loneliness

Loneliness, an established risk factor for both, mental and physical morbidity, is a mounting public health concern. However, the neurobiological mechanisms underlying loneliness-related morbidity are not yet well defined. Here we examined the role of genes and associated DNA risk polymorphic variants that are implicated in loneliness via genetic and epigenetic mechanisms and may thus point to specific therapeutic targets. Searches were conducted on PubMed, Medline, and EMBASE databases using specific Medical Subject Headings terms such as loneliness and genes, neuro- and epigenetics, addiction, affective disorders, alcohol, anti-reward, anxiety, depression, dopamine, cancer, cardiovascular, cognitive, hypodopaminergia, medical, motivation, (neuro)psychopathology, social isolation, and reward deficiency. The narrative literature review yielded recursive collections of scientific and clinical evidence, which were subsequently condensed and summarized in the following key areas: (1) Genetic Antecedents: Exploration of multiple genes mediating reward, stress, immunity and other important vital functions; (2) Genes and Mental Health: Examination of genes linked to personality traits and mental illnesses providing insights into the intricate network of interaction converging on the experience of loneliness; (3) Epigenetic Effects: Inquiry into instances of loneliness and social isolation that are driven by epigenetic methylations associated with negative childhood experiences; and (4) Neural Correlates: Analysis of loneliness-related affective states and cognitions with a focus on hypodopaminergic reward deficiency arising in the context of early life stress, eg, maternal separation, underscoring the importance of parental support early in life. Identification of the individual contributions by various (epi)genetic factors presents opportunities for the creation of innovative preventive, diagnostic, and therapeutic approaches for individuals who cope with persistent feelings of loneliness. The clinical facets and therapeutic prospects associated with the current understanding of loneliness, are discussed emphasizing the relevance of genes and DNA risk polymorphic variants in the context of loneliness-related morbidity.

Loneliness, Depression, and Genetics in the Elderly: Prognostic Factors of a Worse Health Condition?

Loneliness is considered a prognostic factor for poorer health status in the elderly. It is proposed to analyze the role of loneliness in health status in terms of various factors. A total of 1747 individuals from the pilot survey of the Aging in Spain Longitudinal Study (ELES-PS) were reviewed. ELES is a cross-sectional study for collecting health variables, food habits, socioeconomic data, and cognitive and functional capacities, which was carried out on a Spanish representative sample of noninstitutionalized persons of 50 years of age or older. Moreover, since telomere shortening is associated with cellular senescence, 35 telomere-related SNPs and cognitive impairments were analyzed. The results characterize the "solos" as males of 50-60 years, who were overweight and had lower levels of hemoglobin and neutrophils. There is also an association between five SNPs related to telomere length and BDNF. A group of people with loneliness and depression was identified with poorer health and cognitive status, poorer perception of their quality of life, poorer quality of sleep, and lower physical activity. Therefore, it follows that telomeres and BDNF play a role as intermediaries between loneliness and depression and their relationship with a worse state of health.

Understanding loneliness in the twenty-first century: an update on correlates, risk factors, and potential solutions

PURPOSE

Loneliness is increasingly recognised as the next critical public health issue. A plausible reason for this concern may be related to emerging societal trends affecting the way we relate, communicate, and function in our social environment. In 2006, a prominent review of the clinical significance of loneliness was published. However, there has not been a comprehensive update on known and emerging risk factors and correlates of loneliness since then. Furthermore, there is no conceptual model that has been developed to better account for the complexity of loneliness and to inform the development of evidence-based solutions as we challenge the issues of the twenty-first century.

METHODS

We reviewed the current literature to identify either known or emerging risk factors and correlates of loneliness since 2006. This includes new or known evidence on: (1) demography; (2) health, including physical health; mental health; cognitive health; brain, biology, and genetics; and (3) socio-environmental factors including digital communication and the workplace.

RESULTS

We synthesized the literature according to a new proposed conceptual model of loneliness which showed the interplay between known and emerging correlates and risk factors from demography, health, to socio-environmental factors. In the conceptual model of loneliness, we illustrated how solutions can be delivered and tailored to an individual based on their life circumstances and preferences.

CONCLUSION

We concluded by making specific recommendations in advancing our scientific understanding of loneliness. Our knowledge can only be deepened if we increase scientific rigour via accounting for confounding variables and using longitudinal, multi-disciplinary, and multiple methodologies in research. We also call for the rigorous evaluation of programs targeting loneliness.

A SNP, Gene, and Polygenic Risk Score Approach of Oxytocin-Vasopressin Genes in Adolescents' Loneliness

Not much is known regarding underlying biological pathways to adolescents' loneliness. Insight in underlying molecular mechanisms could inform intervention efforts aimed at reducing loneliness. Using latent growth curve modeling, baseline levels and development of loneliness were studied in two longitudinal adolescent samples. Genes (OXTR, OXT, AVPR1A, AVPR1B) were examined using SNP-based, gene-based, and polygenic risk score (PRS) approaches. In both samples, SNP- and gene-based tests showed involvement of the OXTR gene in development of loneliness, though, significance levels did not survive correction for multiple testing. The PRS approach provided no evidence for relations with loneliness. We recommend alternative phenotyping methods, including environmental factors, to consider epigenetic studies, and to examine possible endophenotypes in relation to adolescents' loneliness.

Genetic Contributions to Loneliness and Their Relevance to the Evolutionary Theory of Loneliness

Loneliness is a negative and distressing emotional state that arises from a discrepancy between one's desired and achieved levels of social connectedness. The evolutionary theory of loneliness (ETL) posits that experiencing loneliness is an inherited adaptation that signals that salutary social relations are endangered or damaged and prompts people to reconnect to significant others. The basic tenets of the ETL has led researchers to examine the genetic underpinnings of loneliness. The current review provides an updated overview of genetic studies on loneliness and discusses the importance of genetic research for the ETL. The most recent studies suggest that the many genes that contribute to a small degree to differences in loneliness partially overlap with genes that contribute to neuroticism, but not with depression. In addition, the genetic studies discussed in this review show that genes are unlikely to have a direct effect on loneliness. Instead, environmental factors determine in a dynamic fashion how genes that contribute to loneliness are expressed. Future research on epigenetic processes, such as DNA methylation, can further elucidate the dynamic interplay between genes and the environment and how this interplay contributes to loneliness.

Associations between Oxytocin Receptor (OXTR) Genotype and Elementary School Children's Likability, Dis-likability and Friendship among Classroom Peers: A Longitudinal Study

The single nucleotide polymorphism rs53576 of the oxytocin receptor (OXTR) gene is involved in forming and maintaining relationships in various social contexts. However, this has not been studied in the childhood peer context. The present study followed 359 children (51.6% girls) from age 9 to 12 to explore associations between OXTR rs53576 genotype (i.e., AA, AG or GG genotype) and three indicators of children’s relationships with peers: likability and dis-likability among, and friendship with, classroom peers. Our results showed that OXTR rs53576 was associated with likability among boys, but not with dis-likability and friendship or among girls. Boys with an A and a G allele (i.e., AG genotype) became increasingly more liked by their peers across the four-year studied period than those with two A alleles or two G alleles (i.e., AA and GG genotype). This study indicates that OXTR rs53576 genotype might influence children’s peer relationships, particularly their likeability among peers. Associations between OXTR rs53576 and peer relationships may differ depending on children’s sex and the specific type of peer-relationship under scrutiny.

OXTR polymorphism in depression and completed suicide-A study on a large population sample

In the light of contradictory results concerning OXTR polymorphism rs53576 and depression, we decided to verify the potential association between the two on 1) a large, ethnically homogenous sample of 1185 individuals who completed the Beck Depression Inventory (BDI), as well as on 2) a sample of 763 suicide victims. In the population sample, AA males showed significantly lower BDI scores (p=0.005, p_cor=0.030). Exploratory analyses suggested that this effect was limited to a subgroup within 0-9 BDI score range (p=0.0007, U-Mann Whitney test), whereas no main effect on depressive symptoms (BDI>9) was found. In the suicide sample no association with rs53576 genotype was present. Exploratory analyses in suicides revealed higher blood alcohol concentration (BAC) among AA than GG/GA males (p=0.014, U-Mann Whitney test). Our results show that the OXTR rs53576 variant modulates the mood in male individuals and may positively correlate with alcohol intake among male suicides, but is not associated with suicide or depression. The study adds to the growing knowledge on rs53576 genotype characteristics.

Attachment style and oxytocin receptor gene variation interact in influencing social anxiety

OBJECTIVES

Social anxiety has been suggested to be promoted by an insecure attachment style. Oxytocin is discussed as a mediator of trust and social bonding as well as a modulator of social anxiety. Applying a gene-environment (G × E) interaction approach, in the present pilot study the main and interactive effects of attachment styles and oxytocin receptor (OXTR) gene variation were probed in a combined risk factor model of social anxiety in healthy probands.

METHODS

Participants (N = 388; 219 females, 169 males; age 24.7 ± 4.7 years) were assessed for anxiety in social situations (Social Phobia and Anxiety Inventory) depending on attachment style (Adult Attachment Scale, AAS) and OXTR rs53576 A/G genotype.

RESULTS

A less secure attachment style was significantly associated with higher social anxiety. This association was partly modulated by OXTR genotype, with a stronger negative influence of a less secure attachment style on social anxiety in A allele carriers as compared to GG homozygotes.

CONCLUSIONS

The present pilot data point to a strong association of less secure attachment and social anxiety as well as to a gene-environment interaction effect of OXTR rs53576 genotype and attachment style on social anxiety possibly constituting a targetable combined risk marker of social anxiety disorder.

Oxytocin Pathway Genes: Evolutionary Ancient System Impacting on Human Affiliation, Sociality, and Psychopathology

Oxytocin (OT), a nonapeptide signaling molecule originating from an ancestral peptide, appears in different variants across all vertebrate and several invertebrate species. Throughout animal evolution, neuropeptidergic signaling has been adapted by organisms for regulating response to rapidly changing environments. The family of OT-like molecules affects both peripheral tissues implicated in reproduction, homeostasis, and energy balance, as well as neuromodulation of social behavior, stress regulation, and associative learning in species ranging from nematodes to humans. After describing the OT-signaling pathway, we review research on the three genes most extensively studied in humans: the OT receptor (OXTR), the structural gene for OT (OXT/neurophysin-I), and CD38. Consistent with the notion that sociality should be studied from the perspective of social life at the species level, we address human social functions in relation to OT-pathway genes, including parenting, empathy, and using social relationships to manage stress. We then describe associations between OT-pathway genes with psychopathologies involving social dysfunctions such as autism, depression, or schizophrenia. Human research particularly underscored the involvement of two OXTR single nucleotide polymorphisms (rs53576, rs2254298) with fewer studies focusing on other OXTR (rs7632287, rs1042778, rs2268494, rs2268490), OXT (rs2740210, rs4813627, rs4813625), and CD38 (rs3796863, rs6449197) single nucleotide polymorphisms. Overall, studies provide evidence for the involvement of OT-pathway genes in human social functions but also suggest that factors such as gender, culture, and early environment often confound attempts to replicate first findings. We conclude by discussing epigenetics, conceptual implications within an evolutionary perspective, and future directions, especially the need to refine phenotypes, carefully characterize early environments, and integrate observations of social behavior across ecological contexts.

The genetics of loneliness: linking evolutionary theory to genome-wide genetics, epigenetics, and social science

As a complex trait, loneliness is likely to be influenced by the interplay of numerous genetic and environmental factors. Studies in behavioral genetics indicate that loneliness has a sizable degree of heritability. Candidate-gene and gene-expression studies have pointed to several genes related to neurotransmitters and the immune system. The notion that these genes are related to loneliness is compatible with the basic tenets of the evolutionary theory of loneliness. Research on gene-environment interactions indicates that social-environmental factors (e.g., low social support) may have a more pronounced effect and lead to higher levels of loneliness if individuals carry the sensitive variant of these candidate genes. Currently, there is no extant research on loneliness based on genome-wide association studies, gene-environment-interaction studies, or studies in epigenetics. Such studies would allow researchers to identify networks of genes that contribute to loneliness. The contribution of genetics to loneliness research will become stronger when genome-wide genetics and epigenetics are integrated and used along with well-established methods in psychology to analyze the complex process of gene-environment interplay.

Involvement of the BDNF gene in loneliness in adolescence: a report of opposite gene effects in boys and girls

Previous research has shown that loneliness has a heritable component and that genes within the serotonin-, dopamine-, and oxytocin systems are related to loneliness in adolescence. In the present study, the relation between the BDNF Val66Met polymorphism and loneliness in adolescent boys and girls was examined in a longitudinal study spanning five annual waves (N = 305). Latent growth curve modeling (LGCM) was used to examine the baseline level and the change in loneliness over time. The main finding was that the BDNF gene was not related to loneliness in the total sample. A BDNF by sex interaction was found, in that Met carrying girls had the highest levels of loneliness at baseline, whereas in boys the ValVal genotype was related to higher levels of loneliness. Our results underline the importance of sex-stratified analyses when examining effects of the BDNF genotype and the necessity of conducting gene studies to intermediate phenotypes of loneliness.

The oxytocin receptor gene (OXTR) in relation to state levels of loneliness in adolescence: evidence for micro-level gene-environment interactions

Previous research has shown that the rs53576 variant of the oxytocin receptor gene (OXTR) is associated with trait levels of loneliness, but results are inconsistent. The aim of the present study is to examine micro-level effects of the OXTR rs53576 variant on state levels of loneliness in early adolescents. In addition, gene-environment interactions are examined between this OXTR variant and positive and negative perceptions of company. Data were collected in 278 adolescents (58% girls), by means of the Experience Sampling Method (ESM). Sampling periods consisted of six days with nine assessments per day. A relation was found between the OXTR rs53576 variant and state loneliness, in girls only. Girls carrying an A allele had higher levels of state loneliness than girls carrying the GG genotype. In addition, adolescents with an A allele were more affected by negative perceptions of company than GG carriers, on weekend days only. No significant gene-environment interactions were found with positive company. Adolescents carrying an A allele were more susceptible to negative environments during weekend days than GG carriers. Our findings emphasize the importance of operationalizing the phenotype and the environment accurately.