Genetic and environmental contributions to loneliness in adults: the Netherlands twin register study

Shared genetics and causal relationship between sociability and the brain's default mode network

BACKGROUND

The brain's default mode network (DMN) plays a role in social cognition, with altered DMN function being associated with social impairments across various neuropsychiatric disorders. However, the genetic basis linking sociability with DMN function remains underexplored. This study aimed to elucidate the shared genetics and causal relationship between sociability and DMN-related resting-state functional MRI (rs-fMRI) traits.

METHODS

We conducted a comprehensive genomic analysis using large-scale genome-wide association study (GWAS) summary statistics for sociability and 31 activity and 64 connectivity DMN-related rs-fMRI traits (N = 34,691-342,461). We performed global and local genetic correlations analyses and bi-directional Mendelian randomization (MR) to assess shared and causal effects. We prioritized genes influencing both sociability and rs-fMRI traits by combining expression quantitative trait loci MR analyses, the CELLECT framework - integrating single-nucleus RNA sequencing (snRNA-seq) data with GWAS - and network propagation within a protein-protein interaction network.

RESULTS

Significant local genetic correlations were identified between sociability and two rs-fMRI traits, one representing spontaneous activity within the temporal cortex, the other representing connectivity between the cingulate and angular/temporal cortices. MR analyses suggested potential causal effects of sociability on 12 rs-fMRI traits. Seventeen genes were highly prioritized, with LINGO1, ELAVL2, and CTNND1 emerging as top candidates. Among these, DRD2 was also identified, serving as a robust internal validation of our approach.

CONCLUSIONS

By combining genomic and transcriptomic data, our gene prioritization strategy may serve as a blueprint for future studies. Our findings can guide further research into the biological mechanisms underlying sociability and its role in the development, prognosis, and treatment of neuropsychiatric disorders.

The impact of unmet community service demand on the loneliness of older adults: based on CLHLS (2008-2018)

PURPOSE

To explore the impact of unmet community service demands on loneliness among older adults.

METHODS

Based on the longitudinal tracking data of CLHLS (2008-2018), latent growth curve model (LGCM) was used to describe the trajectory of loneliness among older adults. Panel regression was used to analyze the impact of unmet community service demands on loneliness, and latent classification analysis (LCA) was used to classify the older adults and analyze the differences in loneliness among different types of older adults.

RESULTS

A total of 1445 older people participated in all four surveys, and 22.4% of them reported feeling lonely. From 2008 to 2018, there was a significant non-linear increase in loneliness, with average values of 1.77, 1.81, 1.83, and 1.96, respectively. The level of community service supply (1.31) was far from meeting the demand level (5.11). Unmet community service demands were associated with a higher prevalence of loneliness (β = 0.012, P = 0.003, 95% CI = [0.004, 0.020]). In addition, according to the demand difference for community services, older adults were classified into the comprehensive demand type (Type I) and the medical demand type (Type II). The loneliness of Type I older adults was significantly higher than that of Type II (P < 0.05).

CONCLUSIONS

With the passage of time, loneliness of older adults is showing an accelerating upward trend. Unmet community services can lead to enhanced loneliness among older adults, and the higher the demand for community services, the stronger the loneliness. The government should increase the supply of community services to meet the basic and socio-emotional needs of the older adults to reduce loneliness.

Exome sequencing identifies protein-coding variants associated with loneliness and social isolation

BACKGROUND

Loneliness and social isolation are serious yet underappreciated public health problems, with their genetic underpinnings remaining largely unknown. We aimed to explore the role of protein-coding variants in the manifestation of loneliness and social isolation.

METHODS

We conducted the first exome-wide association analysis on loneliness and social isolation, utilizing 336,115 participants of white-British ancestry for loneliness and 346,115 for social isolation. Sensitivity analyses were performed to validate the genetic findings. We estimated the genetic burden heritability of loneliness and social isolation and provided biological insights into them.

RESULTS

We identified six novel risk genes (ANKRD12, RIPOR2, PTEN, ARL8B, NF1, and PIMREG) associated with loneliness and two (EDARADD and GIGYF1) with social isolation through analysis of rare coding variants. Brain-wide association analysis uncovered 47 associations between identified genes and brain structure phenotypes, many of which are critical for social processing and interaction. Phenome-wide association analysis established significant links between these genes and phenotypes across five categories, mostly blood biomarkers and cognitive measures.

LIMITATIONS

The measurements of loneliness and social isolation in UK Biobank are brief for these multi-layer social factors, some relevant aspects may be missed.

CONCLUSIONS

Our study revealed 13 risk genes associated with loneliness and 6 with social isolation, with the majority being novel discoveries. These findings advance our understanding of the genetic basis of these two traits. The study provides a foundation for future studies aimed at exploring the functional mechanisms of these genes and their potential implications for public health interventions targeting loneliness and social isolation.

Social isolation, loneliness, and their joint effects on cognitive decline and incident Alzheimer's disease: Findings from the Chicago health and aging project

BACKGROUND

There has been contradictory evidence on the prospective associations between social isolation/loneliness (SI/L) and cognitive decline (CD). There is also a scarcity of large and diverse population-based cohort studies examining SI/L that have confirmed clinical diagnoses of Alzheimer's Disease (AD). Notably, beyond individual associations, whether the effects of SI/L compound and accelerate CD and incident AD are not known.

OBJECTIVES

We hypothesized that SI and L, independently, would be associated with CD and incident AD to a similar extent, and the association of SI with CD and incident AD would be higher in lonely older adults.

DESIGN

Prospective cohort study.

SETTING

Urban Chicago areas.

PARTICIPANTS

We analyzed data in the Chicago Health and Aging Project (CHAP), which comprised 7,760 biracial community-dwelling older adults [mean age (standard deviation (SD))=72.3 (6.3); 64 % Black & 63 % women; mean (SD) of follow-up=7.9 (4.3) years].

INTERVENTION (IF ANY)

NA MEASUREMENTS: Linear mixed and logistic regression models were used to regress CD and incident AD separately on the SI index/L.

RESULTS

SI index and L were significantly associated with CD, with one-point increase of beta estimate (SE, p-value) = -0.002 (0.001,0.022) and -0.012 (0.003,<0.001), respectively. Given that the SI index ranges from 0 to 5 and the L from 0 to 1, they had similar effect sizes. Similarly, there were significant associations between SI index and incident AD, odds ratio (95 % CI, p-value) = 1.183 (1.016-1.379,0.029), and between L and incident AD, 2.117 (1.227-3.655,0.006). When stratified by loneliness status, compared to older adults who were not isolated and not lonely, older adults who reported being socially isolated and not lonely experienced accelerated CD, -0.003 (0.001,0.004), despite no significantly increased odds of incident AD.

CONCLUSIONS

SI/L had significant associations with CD and incident AD. Notably, socially isolated older adults who reported not being lonely appeared to be most socially vulnerable to CD. These findings suggest a specific at-risk subgroup of socially vulnerable older adults for future targeted interventions to improve cognitive health.

Epigenome-wide association study of loneliness in a sample of U.S. middle-aged twins

Loneliness is a complex human trait that is highly polygenic and found to affect gene expression related to inflammatory and immunological functioning. To date, no epigenome-wide association studies of loneliness have tested whether differentially methylated sites are annotated to genes associated with inflammatory and immunological processes. Using 281 individual adult twins' DNA methylation data from the Louisville Twin Study, we performed an epigenome-wide analysis of loneliness to address this gap in the literature. In the discovery analysis, 169 twins were used to prioritize probes and test associations with DNA methylation age acceleration, and 56 independent monozygotic (MZ) twin pairs (112 individuals) were used in a within-family replication analysis. Among the 837,274 sites analyzed, no probe sites were statistically significant at the genome-wide level (p < 5.97 × 10-8), but 25 suggestive sites (p < 5 × 10-5) were annotated to genes related to various biological processes, including inflammatory response and protein-binding functions that extend prior findings. The nominal associations at these suggestive probe sites were highly correlated (r = .72) between the discovery sample and the MZ pair replication sample. Finally, loneliness significantly correlated with the DunedinPACE DNA methylation measure, suggesting that higher levels of loneliness were associated with accelerated epigenetic age as quantified by a measure that indexes longitudinal changes across multiple organ systems.

A Life Course, Intergenerational Perspective on Loneliness

The present study relied on 15 dyads of adult children and their older parent to better understand intergenerational family relations from a life course perspective. Interviews were analyzed relying on qualitative thematic analysis, identifying similarities and differences within and between interviews and dyads. Our analysis resulted in three major themes. The first concerns the important role of intergenerational family relation as a means to define and conceptualize the experiences of loneliness and ways of coping with loneliness. The second theme concerned intergenerational relations as a cause (and at times a remedy) of loneliness. The third theme concerns the ability of the dyad's members to reflect on the level of loneliness of the other member in the intergenerational dyad. The findings stress the importance of intergenerational family relations throughout the life course and highlight the importance of adopting an intergenerational lens as a possible means to address loneliness.

Disentangling the Longitudinal Relationship between Loneliness and Depressive Symptoms in U.S. Adults Over 50

OBJECTIVES

A seminal study on loneliness and depression suggested that loneliness influences depression more than the reverse. However, the study's analytic method has since been criticized for failing to account for the trait-like nature of variables. This study aimed to examine the longitudinal relationship between loneliness and depressive symptoms while accounting for the trait-like nature of both variables.

METHODS

Data (n = 16,478) came from the Health and Retirement Study (2006-2016). Measures included the Hughes Loneliness Scale and a modified Center for Epidemiologic Studies Depression scale (loneliness item omitted). Analyses consisted of random intercepts cross-lagged panel models (three time-points evenly spaced across eight years).

RESULTS

There was evidence that loneliness and depressive symptoms are trait-like and these trait-like components are strongly associated. There was not evidence of cross-lagged effects between loneliness and depressive symptoms.

CONCLUSIONS

A tendency toward loneliness corresponded with a tendency toward depressive symptoms. However, deviations in one's typical level of loneliness did not predict deviations in one's typical level of depressive symptoms or vice-versa. These findings do not support past assertions that loneliness shapes subsequent depression more than the reverse.

CLINICAL IMPLICATIONS

By middle to late adulthood, loneliness and depressive symptoms are trait-like phenomena that are strongly associated.

Correlations between Dementia and Loneliness

This review describes associations between dementia and loneliness on the neurobiological and epidemiological levels according to the recent body of literature. The aim of this study was to highlight major lines of research in this field. Sociocognitive skills and social interactions present complex interdependencies with dementia which may be explained by two theories. According to the first one, not sufficiently engaging in social or cognitive activities results in brain atrophy. The second one claims that brain neurogenesis and synaptic density are being increased by social connections. The relationship between loneliness and dementia could be mediated by sensory loss, including hearing and visual impairment, as well as depression and psychotic symptoms. Loneliness itself might cause a depletion in sensory and cognitive stimulation which results in a decrease in neural reserve. Certain changes in the structures of the brain caused by loneliness were found in imaging examination. Loneliness appears to be a crucial risk factor for dementia in recent times due to the modern lifestyle and consequences of the outbreak of COVID-19. Additional studies are required to understand more completely the key tenets of this topic and therefore to improve the prevention and treatment of dementia.

Evidence for a shared genetic contribution to loneliness and borderline personality disorder

Loneliness, influenced by genetic and environmental factors such as childhood maltreatment, is one aspect of interpersonal dysfunction in Borderline Personality Disorder (BPD). Numerous studies link loneliness and BPD and twin studies indicate a genetic contribution to this association. The aim of our study was to investigate whether genetic predisposition for loneliness and BPD risk overlap and whether genetic risk for loneliness contributes to higher loneliness reported by BPD patients, using genome-wide genotype data. We assessed the genetic correlation of genome-wide association studies (GWAS) of loneliness and BPD using linkage disequilibrium score regression and tested whether a polygenic score for loneliness (loneliness-PGS) was associated with case-control status in two independent genotyped samples of BPD patients and healthy controls (HC; Witt2017-sample: 998 BPD, 1545 HC; KFO-sample: 187 BPD, 261 HC). In the KFO-sample, we examined associations of loneliness-PGS with reported loneliness, and whether the loneliness-PGS influenced the association between childhood maltreatment and loneliness. We found a genetic correlation between the GWAS of loneliness and BPD in the Witt2017-sample (rg = 0.23, p = 0.015), a positive association of loneliness-PGS with BPD case-control status (Witt2017-sample: NkR² = 2.3%, p = 2.7*10-12; KFO-sample: NkR² = 6.6%, p = 4.4*10-6), and a positive association between loneliness-PGS and loneliness across patient and control groups in the KFO-sample (β = 0.186, p = 0.002). The loneliness-PGS did not moderate the association between childhood maltreatment and loneliness in BPD. Our study is the first to use genome-wide genotype data to show that the genetic factors underlying variation in loneliness in the general population and the risk for BPD overlap. The loneliness-PGS was associated with reported loneliness. Further research is needed to investigate which genetic mechanisms and pathways are involved in this association and whether a genetic predisposition for loneliness contributes to BPD risk.

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 and its associated factors among university students during late stage of COVID-19 pandemic: An online cross-sectional study

BACKGROUND

The COVID-19 pandemic resulted in a number of psychosocial and emotional catastrophes, including loneliness. The associated lockdowns, reduced social support, and insufficiently perceived interactions are expected to heighten the level of loneliness during the pandemic. However, there is a dearth of evidence regarding the level of loneliness and what correlates with loneliness among university students in Africa, particularly in Ethiopia.

OBJECTIVES

The general objective of this study was to assess the prevalence and associated factors of loneliness among university students during the COVID-19 pandemic in Ethiopia.

METHODS

A cross-sectional study was undertaken. An online data collection tool was distributed to voluntary undergraduate university students. The sampling technique used was snowball sampling. Students were requested to pass the online data collection tool to at least one of their friends to ease data collection. SPSS version 26.0 was used for data analysis. Both descriptive and inferential statistics were used to report the results. Binary logistic regression was used to identify factors associated with loneliness. A P-value less than 0.2 was used to screen variables for the multivariable analysis, and a P-value less than 0.05 was used to declare significance in the final multivariable logistic regression.

RESULT

A total of 426 study participants responded. Out of the total, 62.9% were males, and 37.1% attended fields related to health. Over three-fourths (76.5%) of the study participants encountered loneliness. Females (adjusted odds ratio (AOR): 1.75; 95% confidence interval (CI): 1.01, 3.04), non-health-related departments (AOR: 1.94; 95% CI: 1.17, 3.35), ever encountering sexual harassment (AOR: 3.32; 95% CI: 1.46, 7.53), sleeping problems (AOR: 2.13; 95% CI: 1.06, 4.30), perceived stress (AOR: 6.40; 95% CI: 1.85, 22.19) and poor social support (AOR: 3.13; 95% CI: 1.10, 8.87) were significantly associated with loneliness.

CONCLUSION AND RECOMMENDATION

A significant proportion of students were victims of loneliness during the COVID-19 pandemic. Being female, working in non-health-related fields, having sleeping problems, encountering sexual harassment, perceived stress, and poor social support were significantly associated with loneliness. Interventions to reduce loneliness should focus on related psychosocial support to reduce stress, sleeping disturbances, and poor social support. A special focus should also be given to female students.

Loneliness and problematic social networking sites use in young adults with poor vs. good sleep quality: The moderating role of gender

Despite the evidence of a relationship between loneliness, problematic social networking sites use (PSNSU), and sleep quality, associations between specific PSNSU symptoms and loneliness in individuals with poor vs. good sleep quality and possible gender differences have yet to be understood. We examined the relationships between loneliness and PSNSU symptoms (i.e., preference for online social interaction - POSI, mood regulation, deficient self-regulation, and negative outcomes), and possible moderating effects of gender for individuals with poor vs. good sleep quality. Seven hundred and sixty-three young adults completed an online survey including self-report measures of sleep quality, loneliness, and PSNSU symptoms. Individuals with poor sleep quality reported higher levels of loneliness and greater scores on all PSNSU domains than those with good sleep quality. Slope analyses revealed that in men vs. women with poor sleep quality, greater deficient self-regulation of social networking sites use was associated with lower levels of loneliness. Conversely, in men vs. women with good sleep quality, greater POSI was associated with higher levels of loneliness. Our findings showed that individuals with poor sleep quality are characterized by higher levels of loneliness and more severe PSNSU symptoms that may be the result of sleep disturbance-related metabolic, neural, and hormonal processes. Moreover, our results highlight gender differences for individuals with poor vs. good sleep quality which may help clarify the nature of the association between loneliness and PSNSU.

Identifying novel proteins underlying loneliness by integrating GWAS summary data with human brain proteomes

Enduring loneliness is associated with mental disorders and physical diseases. Although genome-wide association studies (GWAS) have identified risk loci associated with loneliness, how these loci confer the risk remains largely unknown. In the current study, we aimed to investigate key proteins underlying loneliness in the brain by integrating human brain proteomes and transcriptomes with loneliness GWAS to perform a discovery proteome-wide association study (PWAS), followed by a confirmatory PWAS, transcriptome-wide association analysis (TWAS), Mendelian randomization (MR), Steigering filtering analysis and Bayesian colocalization analysis. Moreover, given the fact that loneliness is associated with mental disorders, we explored the shared genetic architecture between loneliness and mental disorders. Totally, we identified 18 genes to be associated with loneliness via their cis-regulated brain protein abundance. Eleven of the 18 genes (61.1%) were replicated in the confirmatory PWAS, and mRNA levels of 4 genes were further validated to be associated with loneliness.MR and genetic colocalization analysis further confirmed that the increased protein abundance of ALDH2 and ICA1L was protective against loneliness, while the increased protein abundance of GPX1 was a risk for developing loneliness. Furthermore, we found genetic correlations, bidirectional causal associations and overlapping phenotype-associated protein profiles between loneliness and mental disorders including major depression and schizophrenia. In summary, our findings provided clues about the brain-related molecular basis underlying loneliness, which warrants further investigation.

Genetic and environmental contributions to the subjective burden of social isolation during the COVID-19 pandemic

BACKGROUND

Feelings of loneliness and the burden of social isolation were among the most striking consequences of widespread containment measures, such as "social distancing", during the COVID-19 pandemic. Because of the potential impact on people's health, there has been increased interest in understanding the mechanisms and factors that contributed to feelings of loneliness and the burdens of social isolation. However, in this context, genetic predisposition has been largely ignored as an important factor. This is problematic because some of the phenotypic associations observed to date may in fact be genetic. The aim of this study is, therefore, to examine the genetic and environmental contributions to the burden of social isolation at two time points during the pandemic. In addition, we examine whether risk factors identified in previous studies explain genetic or environmental contributions to the burden of social isolation.

METHODS

The present study is based on a genetically sensitive design using data from the TwinLife panel study, which surveyed a large sample of adolescent and young adult twins during the first (N = 798) and the second (N = 2520) lockdown in Germany.

RESULTS

We find no substantive differences in genetic and environmental contributions to social isolation burden over the course of the pandemic. However, we find the determinants highlighted as important in previous studies can explain only a small proportion of the observed variance in the burden of social isolation and mainly explained genetic contributions.

CONCLUSIONS

While some of the observed associations appear to be genetic, our findings underscore the need for further research, as the causes of individual differences in burden of social isolation remain unclear.

Breaking the vicious cycle: The interplay between loneliness, metabolic illness, and mental health

Loneliness, or perceived social isolation, is a leading predictor of all-cause mortality and is increasingly considered a public health epidemic afflicting significant portions of the general population. Chronic loneliness is itself associated with two of the most pressing public health epidemics currently facing the globe: the rise of mental illness and metabolic health disorders. Here, we highlight the epidemiological associations between loneliness and mental and metabolic health disorders and argue that loneliness contributes to the etiology of these conditions by acting as a chronic stressor that leads to neuroendocrine dysregulation and downstream immunometabolic consequences that manifest in disease. Specifically, we describe how loneliness can lead to overactivation of the hypothalamic-pituitary-adrenal axis and ultimately cause mitochondrial dysfunction, which is implicated in mental and metabolic disease. These conditions can, in turn, lead to further social isolation and propel a vicious cycle of chronic illness. Finally, we outline interventions and policy recommendations that can reduce loneliness at both the individual and community levels. Given its role in the etiology of the most prevalent chronic diseases of our time, focusing resources on alleviating loneliness is a vitally important and cost-effective public health strategy.

Social isolation, loneliness and mental health sequelae of the Covid-19 pandemic in Parkinson's disease

People living with Parkinson Disease (PwP) have been at risk for the negative effects of loneliness even before the Coronavirus Disease 2019 (Covid-19) pandemic. Despite some similarities with previous outbreaks, the Covid-19 pandemic is significantly more wide-spread, long-lasting, and deadly, which likely means demonstrably more negative mental health issues. Although PwP are not any more likely to contract Covid-19 than those without, the indirect negative sequelae of isolation, loneliness, mental health issues, and worsening motor and non-motor features remains to be fully realized. Loneliness is not an isolated problem; the preliminary evidence indicates that loneliness associated with the Covid-19 restrictions has dramatically increased in nearly all countries around the world.

Lacking Social Support is Associated With Structural Divergences in Hippocampus-Default Network Co-Variation Patterns

Elaborate social interaction is a pivotal asset of the human species. The complexity of people’s social lives may constitute the dominating factor in the vibrancy of many individuals’ environment. The neural substrates linked to social cognition thus appear especially susceptible when people endure periods of social isolation: here, we zoom in on the systematic inter-relationships between two such neural substrates, the allocortical hippocampus (HC) and the neocortical default network (DN). Previous human social neuroscience studies have focused on the DN, while HC subfields have been studied in most detail in rodents and monkeys. To bring into contact these two separate research streams, we directly quantified how DN subregions are coherently co-expressed with specific HC subfields in the context of social isolation. A two-pronged decomposition of structural brain scans from ∼40 000 UK Biobank participants linked lack of social support to mostly lateral subregions in the DN patterns. This lateral DN association co-occurred with HC patterns that implicated especially subiculum, presubiculum, CA2, CA3 and dentate gyrus. Overall, the subregion divergences within spatially overlapping signatures of HC–DN co-variation followed a clear segregation into the left and right brain hemispheres. Separable regimes of structural HC–DN co-variation also showed distinct associations with the genetic predisposition for lacking social support at the population level.

Loneliness is linked to specific subregional alterations in hippocampus-default network covariation

Social interaction complexity makes humans unique. But in times of social deprivation, this strength risks exposure of important vulnerabilities. Human social neuroscience studies have placed a premium on the default network (DN). In contrast, hippocampus (HC) subfields have been intensely studied in rodents and monkeys. To bridge these two literatures, we here quantified how DN subregions systematically covary with specific HC subfields in the context of subjective social isolation (i.e., loneliness). By codecomposition using structural brain scans of ∼40,000 UK Biobank participants, loneliness was specially linked to midline subregions in the uncovered DN patterns. These association cortex patterns coincided with concomitant HC patterns implicating especially CA1 and molecular layer. These patterns also showed a strong affiliation with the fornix white matter tract and the nucleus accumbens. In addition, separable signatures of structural HC-DN covariation had distinct associations with the genetic predisposition for loneliness at the population level.

NEW & NOTEWORTHY The hippocampus and default network have been implicated in rich social interaction. Yet, these allocortical and neocortical neural systems have been interrogated in mostly separate literatures. Here, we conjointly investigate the hippocampus and default network at a subregion level, by capitalizing structural brain scans from ∼40,000 participants. We thus reveal unique insights on the nature of the “lonely brain” by estimating the regimes of covariation between the hippocampus and default network at population scale.

Social Isolation, Loneliness and Well-Being: The Impact of WeChat Use Intensity During the COVID-19 Pandemic in China

This study is aimed to examine the impact of WeChat use intensity on social isolation, loneliness, and well-being during the lockdown period of the COVID-19 pandemic. Drawing on the regulatory loop model of loneliness, the notions of Internet Paradox, the Time Displacement hypothesis and previous literature on WeChat use intensity, we propose that lockdown loneliness (partially) mediates the relationship between lockdown WeChat use intensity and well-being (i.e., lockdown stress and lockdown life satisfaction). Moreover, we assume that lockdown WeChat use intensity moderates the relationship between lockdown social isolation and well-being (i.e., lockdown stress and lockdown life satisfaction) in both a direct and in an indirect way, that is through lockdown loneliness. The results from our Structural Equation Modeling analyses, using a sample of 1,805 Chinese respondents, indicate that all of our research hypotheses are confirmed. From this empirical work, it becomes clear that online social interactions, which are believed by many people to be able to compensate for the lack of offline social interactions during the COVID-19 lockdown period, in fact are endangering their mental health and life satisfaction instead. This article concludes with theoretical and practical implications of our study, followed by its limitations and recommendations for future research.

Genetic underpinnings of sociability in the general population

Levels of sociability are continuously distributed in the general population, and decreased sociability represents an early manifestation of several brain disorders. Here, we investigated the genetic underpinnings of sociability in the population. We performed a genome-wide association study (GWAS) of a sociability score based on four social functioning-related self-report questions from 342,461 adults in the UK Biobank. Subsequently we performed gene-wide and functional follow-up analyses. Robustness analyses were performed in the form of GWAS split-half validation analyses, as well as analyses excluding neuropsychiatric cases. Using genetic correlation analyses as well as polygenic risk score analyses we investigated genetic links of our sociability score to brain disorders and social behavior outcomes. Individuals with autism spectrum disorders, bipolar disorder, depression, and schizophrenia had a lower sociability score. The score was significantly heritable (SNP h2 of 6%). We identified 18 independent loci and 56 gene-wide significant genes, including genes like ARNTL, DRD2, and ELAVL2. Many associated variants are thought to have deleterious effects on gene products and our results were robust. The sociability score showed negative genetic correlations with autism spectrum, disorders, depression, schizophrenia, and two sociability-related traits-loneliness and social anxiety-but not with bipolar disorder or Alzheimer's disease. Polygenic risk scores of our sociability GWAS were associated with social behavior outcomes within individuals with bipolar disorder and with major depressive disorder. Variation in population sociability scores has a genetic component, which is relevant to several psychiatric disorders. Our findings provide clues towards biological pathways underlying sociability.

Mortality risk associated with combinations of loneliness and social isolation. Findings from The Irish Longitudinal Study on Ageing (TILDA)

Background

Social distancing and similar measures in response to the coronavirus disease 2019 pandemic have greatly increased loneliness and social isolation among older adults. Understanding the association between loneliness and mortality is therefore critically important. We examined whether combinations of loneliness and social isolation, using a metric named social asymmetry, was associated with increased mortality risk.

Methods

The sample was derived from participants in The Irish Longitudinal Study on Ageing, a nationally representative sample of community-dwelling older adults aged ≥50. Survey data were linked to official death registration records. Cox proportional hazards regressions and competing risk survival analyses were used to examine the association between social asymmetry and all-cause and cause-specific mortality.

Results

Of four social asymmetry groups, concordant low lonely (low loneliness, low isolation) included 35.5% of participants; 26.4% were concordant high lonely (high loneliness, high isolation); 19.2% were discordant robust (low loneliness, high isolation) and 18.9% discordant susceptible (high loneliness, low isolation). The concordant high lonely (hazard ratio [HR] = 1.43, 95% confidence interval [CI]: 1.09–1.87) and discordant robust (HR = 1.37, 95% CI: 1.04–1.81) groups had an increased mortality risk compared to those in the concordant low lonely group. The concordant high lonely group had an increased risk of mortality due to diseases of the circulatory system (sub-distribution hazard ratio = 1.52, 95% CI: 1.03–2.25).

Conclusion

We found that social asymmetry predicted mortality over a 7-year follow-up period. Our results confirm that a mismatch between subjective loneliness and objective social isolation, as well as the combination of loneliness and social isolation, were associated with an increased all-cause mortality risk.

Polygenic overlap and shared genetic loci between loneliness, severe mental disorders, and cardiovascular disease risk factors suggest shared molecular mechanisms

Clinical and epidemiological evidence suggest that loneliness is associated with severe mental disorders (SMDs) and increases the risk of cardiovascular disease (CVD). However, the mechanisms underlying the relationship between loneliness, SMDs, and CVD risk factors remain unknown. Here we explored overlapping genetic architecture and genetic loci shared between SMDs, loneliness, and CVD risk factors. We analyzed large independent genome-wide association study data on schizophrenia (SCZ), bipolar disorder (BD), major depression (MD), loneliness and CVD risk factors using bivariate causal mixture mode (MiXeR), which estimates the total amount of shared variants, and conditional false discovery rate to evaluate overlap in specific loci. We observed substantial genetic overlap between SMDs, loneliness and CVD risk factors, beyond genetic correlation. We identified 149 loci jointly associated with loneliness and SMDs (MD n = 67, SCZ n = 54, and BD n = 28), and 55 distinct loci jointly associated with loneliness and CVD risk factors. A total of 153 novel loneliness loci were found. Most of the shared loci possessed concordant effect directions, suggesting that genetic risk for loneliness may increase the risk of both SMDs and CVD. Functional analyses of the shared loci implicated biological processes related to the brain, metabolic processes, chromatin and immune system. Altogether, the study revealed polygenic overlap between loneliness, SMDs and CVD risk factors, providing new insights into their shared genetic architecture and common genetic mechanisms.

The association between loneliness and depressive symptoms among adults aged 50 years and older: a 12-year population-based cohort study

BACKGROUND

Loneliness is experienced by a third of older adults in the UK and is a modifiable potential risk factor for depressive symptoms. It is unclear how the association between loneliness and depressive symptoms persists over time, and whether it is independent of related social constructs and genetic confounders. We aimed to investigate the association between loneliness and depressive symptoms, assessed on multiple occasions during 12 years of follow-up, in a large, nationally representative cohort of adults aged 50 years and older in England.

METHODS

We did a longitudinal study using seven waves of data that were collected once every 2 years between 2004 and 2017, from adults aged 50 years and older in the English Longitudinal Study of Ageing (ELSA). The exposure was loneliness at baseline (wave two), measured with the short 1980 revision of the University of California, Los Angeles Loneliness Scale (R-UCLA). The primary outcome was a score indicating severity of depression measured at six subsequent timepoints (waves three to eight), using the eight-item version of the Centre for Epidemiologic Studies Depression Scale (CES-D). Analyses were linear multilevel regressions, before and after adjusting for social isolation, social support, polygenic risk scores, and other sociodemographic and health-related confounders. The secondary outcome was depression diagnosis, measured using a binary version of the CES-D.

FINDINGS

4211 (46%) of 9171 eligible participants had complete data on exposure, outcome, and confounders, and were included in our complete case sample. After all adjustments, a 1-point increase in loneliness score was associated with a 0·16 (95% CI 0·13-0·19) increase in depressive symptom severity score (averaged across all follow-ups). We estimated a population attributable fraction for depression associated with loneliness of 18% (95% CI 12-24) at 1 year of follow-up and 11% (3-19) at the final follow-up (wave eight), suggesting that 11-18% of cases of depression could potentially be prevented if loneliness were eliminated. Associations between loneliness and depressive symptoms remained after 12 years of follow-up, although effect sizes were smaller with longer follow-up.

INTERPRETATION

Irrespective of other social experiences, higher loneliness scores at baseline were associated with higher depression symptom severity scores during 12 years of follow-up among adults aged 50 years and older. Interventions that reduce loneliness could prevent or reduce depression in older adults, which presents a growing public health problem worldwide.

FUNDING

National Institute on Aging and a consortium of UK Government departments coordinated by the National Institute for Health Research.

Genetic and Environmental Causes of Individual Differences in Borderline Personality Disorder Features and Loneliness are Partially Shared

Loneliness is related to mental and somatic health outcomes, including borderline personality disorder. Here, we analyze the sources of variation that are responsible for the relationship between borderline personality features (including four dimensions, affective instability, identity disturbance, negative relationships, self-harm and a total score) and loneliness. Using genetically informative data from two large nonclinical samples of adult twin pairs from Australia and the Netherlands (N = 11,329), we estimate the phenotypic, genetic and environmental correlations between self-reported borderline personality features and loneliness. Individual differences in borderline personality and loneliness were best explained by additive genetic factors with heritability estimates h2 = 41% for the borderline personality total score and h2 = 36% for loneliness, with the remaining variation explained by environmental influences that were not shared by twins from the same pair. Genetic and environmental factors influencing borderline personality (total score and four subscales separately) were also partial causes of loneliness. The correlation between loneliness and the borderline personality total score was rph = .51. The genetic correlation was estimated at rg = .64 and the environmental correlation at re = .40. Our study suggests common etiological factors in loneliness and borderline personality features.

Physical Contact and Loneliness: Being Touched Reduces Perceptions of Loneliness

Objective

This article addresses the connection between loneliness and physical contact. Evolutionary and psychological research has shown that touch is an important part of bond-building and emotion communication; loneliness is intimately related to these elements as well. In this paper, we ask whether physical contact reduces feelings of loneliness —which might derive from evolutionary ancient bonding mechanisms—despite a cultural context that is relatively non-tactile.

Method

An experimental study (40 participants, 13 males) tested for observable effects of touch on loneliness scores in a low-contact culture to analyse whether they respond positively to that stimulus despite cultural training against it.

Results

Participants exposed to physical contact reported significantly lower neglect scores from their close relationships in a short loneliness scale, thus suggesting that there is an underlying mechanism that persists despite enculturation. The effects were particularly strong among single people, which could mean that lower loneliness among married people might be partly explained by the regular availability of physical contact. Participants in the experimental condition also showed a faster reduction in heart rate, interpreted as a sign of physiological wellbeing.

Conclusions

These findings help to specify mechanisms within the evolutionary theoretical framework of loneliness that link internal feelings to environmental cues. This article aims at contributing to a more complex discussion on the interactions between emotions, cultural practices and psychological well-being.

The association between sleep quality and loneliness in rural older individuals: a cross-sectional study in Shandong Province, China

Background

There is a evidence of negative association between loneliness and sleep quality in older adults. However, little is known regarding the relationship between loneliness and sleep quality among Chinese rural older adults. This study examined the associations of loneliness and sleep quality in a cross-sectional study of older adults.

Methods

A face-to-face questionnaire survey was conducted among 1658 rural older adults in Shandong Province, China. Loneliness was assessed using the University of California at Los Angeles Loneliness Scale. Sleep quality was assessed using the Pittsburgh Sleep Quality Index. Ordinal logistic regression was conducted to examine the association of loneliness and sleep quality after adjustment for multiple confounding variables.

Results

After variables such as age, marriage, education, occupation, economic income, family relationships, living arrangement, smoking behavior, alcohol consumption, chronic disease experience, and quality of life were controlled in a multivariable analysis, poor sleep quality was still associated with loneliness in the rural older population.

Conclusion

This finding implied an adverse effect of sleep quality on the loneliness of older adults. Poor sleep quality was associated with increased odds of loneliness in Chinese rural older adults. Sleep-based interventions should be developed to prevent loneliness in rural older adults in China.

Absence and Presence of Human Interaction: The Relationship Between Loneliness and Empathy

Loneliness is the negative experience of a discrepancy between the desired and actual personal network of relationships. Whereas past work have focused on the effect of loneliness on prosocial behaviors, the present research addressed the gap by exploring the effect of loneliness on empathy. Empathy is the emotional reaction of sharing in others' internal experiences. We adopted a new paradigm-empathy selection task, which uses free choices to assess the desire to empathize. Participants made a series of binary choices, selecting situations that instructed them to empathize or objectively describe. Results from two studies showed that, compared to non-lonely people, lonely people were more likely to choose positive empathy but to avoid negative empathy. The pattern occurs because lonely people perceived higher (vs. lower) social support in the positive (vs. negative) empathy tasks. Moreover, empathy served to be an adaptive emotion regulation strategy developed by lonely people to reduce their loneliness effectively. This research has resulted in both theoretical contributions to prosocial behavior literature and the further discovery of practical implications for loneliness intervention.

Predicting Loneliness from Where and What People Do

The many devastating mental health outcomes associated with chronic loneliness is the motivation behind research into examining personal and demographic characteristics of the lonely. The present study sought to examine the connection of where people live (degree of urbanization) and what people do (leisure activities) with self-report of loneliness in a large sample (N = 8356) of unrelated Dutch adults. Information regarding where people live and what they do in their leisure time was entered into a regression analysis for self-reported loneliness. The overall regression was significant and accounted for 2.8% of the loneliness scale scores. Significant independent predictors for loneliness were living in heavily urbanized areas and engaging in fewer social activities. People who went sightseeing or to amusement parks/zoos or who participated in clubs reported being less lonely. Spending time using a computer predicted higher self-report loneliness scores. Consistent with previous research, after controlling for other variables, gender was not a significant predictor of loneliness but both a younger age and a curvilinear or U-shaped curve of age predicted loneliness (the younger and the much older). The results suggest that meaningful interpersonal interactions may result in lower feelings of loneliness.

A critical review and development of a conceptual model of exclusion from social relations for older people

Social exclusion is complex and dynamic, and it leads to the non-realization of social, economic, political or cultural rights or participation within a society. This critical review takes stock of the literature on exclusion of social relations. Social relations are defined as comprising social resources, social connections and social networks. An evidence review group undertook a critical review which integrates, interprets and synthesizes information across studies to develop a conceptual model of exclusion from social relations. The resulting model is a subjective interpretation of the literature and is intended to be the starting point for further evaluations. The conceptual model identifies individual risks for exclusion from social relations (personal attributes, biological and neurological risk, retirement, socio-economic status, exclusion from material resources and migration). It incorporates the evaluation of social relations, and the influence of psychosocial resources and socio-emotional processes, sociocultural, social-structural, environmental and policy contextual influences on exclusion from social relations. It includes distal outcomes of exclusion from social relations, that is, individual well-being, health and functioning, social opportunities and social cohesion. The dynamic relationships between elements of the model are also reported. We conclude that the model provides a subjective interpretation of the data and an excellent starting point for further phases of conceptual development and systematic evaluation(s). Future research needs to consider the use of sophisticated analytical tools and an interdisciplinary approach in order to understand the underlying biological and ecopsychosocial associations that contribute to individual and dynamic differences in the experience of exclusion from social relations.

The Stability and Change of Loneliness Across the Life Span: A Meta-Analysis of Longitudinal Studies

Individuals experience loneliness when they perceive a deficiency in the quality or quantity of their social relationships. In the present meta-analysis, we compiled data from 75 longitudinal studies conducted in Asia, Australia, Europe, and North America (N = 83, 679) to examine the rank-order and mean-level development of loneliness across the life span. Data were analyzed using two- and three-level meta-analyses and generalized additive mixed models. The results indicate that the rank order of loneliness is as stable as the rank order of personality traits and follows an inverted U-shaped trajectory across the life span. Regarding mean-level development, loneliness was found to decrease throughout childhood and to remain essentially stable from adolescence to oldest old age. Thus, in contrast to other personality characteristics, changes in loneliness are not generally related to age. Implications for theory are discussed.

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.

Connectome-based individualized prediction of loneliness

Loneliness is an increasingly prevalent condition linking with enhanced morbidity and premature mortality. Despite recent proposal on medicalization of loneliness, so far no effort has been made to establish a model capable of predicting loneliness at the individual level. Here, we applied a machine-learning approach to decode loneliness from whole-brain resting-state functional connectivity (RSFC). The relationship between whole-brain RSFC and loneliness was examined in a linear predictive model. The results revealed that individual loneliness could be predicted by within- and between-network connectivity of prefrontal, limbic and temporal systems, which are involved in cognitive control, emotional processing and social perceptions and communications, respectively. Key nodes that contributed to the prediction model comprised regions previously implicated in loneliness, including the dorsolateral prefrontal cortex, lateral orbital frontal cortex, ventromedial prefrontal cortex, caudate, amygdala and temporal regions. Our findings also demonstrated that both loneliness and associated neural substrates are modulated by levels of neuroticism and extraversion. The current data-driven approach provides the first evidence on the predictive brain features of loneliness based on organizations of intrinsic brain networks. Our work represents initial efforts in the direction of making individualized prediction of loneliness that could be useful for diagnosis, prognosis and treatment.

The Big Five Personality Traits as Predictors of Loneliness among Older Men in Israel

Loneliness may have complex implications for the mental and physical health of older people. It could have unique expressions among older men due to the social construction of gender, which raises an expectation that men should be strong, assertive, and capable of independently coping with their difficulties. As a result, older men suffering from loneliness may avoid talking about it and seeking help for this matter. The Big Five personality traits were found to be associated with many life domains, including loneliness, yet this issue has received limited research attention with regard to older adults in general and older men in particular. Therefore, the current study explores the contribution of the Big Five personality traits to understanding loneliness among older men in Israel, while controlling for several demographic factors. The data were collected through structured questionnaires administered to a sample of 392 older men. The results indicate that agreeableness, emotional stability, and openness to experiences were negatively associated with older men's loneliness. In addition, no association was found between extraversion and conscientiousness and respondents' loneliness, and no significant association was found between age and loneliness, and being employed and being in a relationship were associated with lower levels of loneliness. The conclusion is that it is important that professionals working with older men utilize the Big Five personality traits to understand loneliness and offer them interventions for reducing their loneliness. Furthermore, it is essential to promote social awareness of the importance of intimate relationships, as well as of employment, in the old age.

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.

Bidirectional Mediating Role of Loneliness in the Association Between Shyness and Generalized Pathological Internet Use in Chinese University Students: A Longitudinal Cross-Lagged Analysis

This 1-year longitudinal study examined the bidirectional mediating role of loneliness in the association between shyness and generalized pathological Internet use (GPIU) in a sample of 291 Chinese university students (143 men, mean age = 19.07 years). A fully cross-lagged panel design was used in which shyness, loneliness, and GPIU were assessed at 3 time points separated by 6-month intervals (named T1, T2, and T3). The results indicated that relationships among shyness, loneliness, and GPIU were dynamic and bidirectional. Specifically, T1 shyness positively predicted increased T2 loneliness, T2 shyness positively predicted increased T3 loneliness, and T2 loneliness positively predicted increased T3 shyness. Additionally, T1 GPIU positively predicted increased T2 loneliness, T2 GPIU positively predicted increased T3 loneliness, and T2 loneliness positively predicted increased T3 GPIU. Loneliness was found to play a bidirectional mediating role in the association between shyness and GPIU. Specifically, T1 shyness and T3 GPIU were mediated through increased loneliness at T2, and T1 GPIU and T3 shyness were mediated through increased loneliness at T2. Furthermore, relationships among shyness, loneliness, and GPIU were the same across the 2 groups, with the strength of relationships being stronger for men.

Predicting loneliness with polygenic scores of social, psychological and psychiatric traits

Loneliness is a heritable trait that accompanies multiple disorders. The association between loneliness and mental health indices may partly be due to inherited biological factors. We constructed polygenic scores for 27 traits related to behavior, cognition and mental health and tested their prediction for self-reported loneliness in a population-based sample of 8798 Dutch individuals. Polygenic scores for major depressive disorder (MDD), schizophrenia and bipolar disorder were significantly associated with loneliness. Of the Big Five personality dimensions, polygenic scores for neuroticism and conscientiousness also significantly predicted loneliness, as did the polygenic scores for subjective well-being, tiredness and self-rated health. When including all polygenic scores simultaneously into one model, only 2 major depression polygenic scores remained as significant predictors of loneliness. When controlling only for these 2 MDD polygenic scores, only neuroticism and schizophrenia remain significant. The total variation explained by all polygenic scores collectively was 1.7%. The association between the propensity to feel lonely and the susceptibility to psychiatric disorders thus pointed to a shared genetic etiology. The predictive power of polygenic scores will increase as the power of the genome-wide association studies on which they are based increases and may lead to clinically useful polygenic scores that can inform on the genetic predisposition to loneliness and mental health.

Childhood physical maltreatment, perceived social isolation, and internalizing symptoms: a longitudinal, three-wave, population-based study

A number of cross-sectional studies have consistently shown a correlation between childhood physical maltreatment, perceived social isolation and internalizing symptoms. Using a longitudinal, three-wave design, this study sought to assess the mediating role of perceived social isolation in adulthood in the association between childhood physical maltreatment and internalizing symptoms in adulthood. The study has a three-wave design. We used data collected from 1994 to 2008 within the framework of the Tromsø Study (N = 4530), a representative prospective cohort study of men and women. Perceived social isolation was measured at a mean age of 54.7 years, and internalizing symptoms were measured at a mean age of 61.7 years. The difference-in-coefficients method was used to assess the indirect effects and the proportion (%) of mediated effects. Childhood physical maltreatment was associated with an up to 68% [relative risk (RR) = 1.68, 95% confidence interval (CI): 1.33-2.13] higher risk of perceived social isolation in adulthood. Childhood physical maltreatment and perceived social isolation in adulthood were associated with greater levels of internalizing symptoms in adulthood (p < 0.01). A dose-response association was observed between childhood physical maltreatment and internalizing symptoms in adulthood (p < 0.001). Perceived social isolation in adulthood mediated up to 14.89% (p < 0.05) of the association between childhood physical maltreatment and internalizing symptoms in adulthood. The results of this study indicate the need to take perceived social isolation into account when considering the impact of childhood physical maltreatment on internalizing symptoms.

Childhood disadvantage, education, and psychological distress in adulthood: A three-wave population-based study

BACKGROUND

We assessed the mediating role of education in the association between childhood disadvantage and psychological distress in adulthood using longitudinal data collected in three waves, from 1994 to 2008, in the framework of the Tromsø Study (N = 4530), a cohort that is representative of men and women from Tromsø.

METHODS

Education was measured at a mean age of 54.7 years, and psychological distress in adulthood was measured at a mean age of 61.7 years. Ordinary least square regression analysis was used to assess the associations between childhood disadvantage, education, and psychological distress in adulthood. The indirect effects and the proportion (%) of indirect effects of childhood disadvantage (via education) on psychological distress in adulthood were assessed by mediation analysis.

RESULTS

Childhood disadvantage was associated with lower education and higher psychological distress in adulthood (p < 0.05). Lower education was associated with a higher psychological distress in adulthood (p < 0.05). A minor proportion (7.51%, p < 0.05) of the association between childhood disadvantage and psychological distress in adulthood was mediated by education.

LIMITATIONS

Childhood disadvantages were measured retrospectively.

CONCLUSION

The association between childhood disadvantage and psychological distress in adulthood is primarily independent of education.

Loneliness in psychosis: a systematic review

PURPOSE

The aim of the review is to understand the relationships between loneliness and related psychological and social factors in individuals with psychosis. Loneliness is poorly understood in people with psychosis. Given the myriad of social challenges facing individuals with psychosis, these findings can inform psychosocial interventions that specifically target loneliness in this vulnerable group.

METHODS

We adhered to the PRISMA guidelines and systematically reviewed empirical studies that measured loneliness either as a main outcome or as an associated variable in individuals with psychosis.

RESULTS

A total of ten studies examining loneliness in people diagnosed with a psychotic disorder were examined. Heterogeneity in the assessment of loneliness was found, and there were contradictory findings on the relationship between loneliness and psychotic symptomatology. In individuals with psychosis, loneliness may be influenced by psychological and social factors such as increased depression, psychosis, and anxiety, poor social support, poor quality of life, more severe internalised stigma and perceived discrimination, and low self-esteem.

CONCLUSIONS

The relationship between loneliness and psychosis remains poorly understood due to a lack of rigorous studies. Although having strong social relationships is crucial to facilitate recovery from serious mental illness, psychosocial interventions that specifically target loneliness in individuals with psychosis are lacking and sorely needed. Interventions targeting loneliness in those with psychosis will also need to account for additional barriers associated with psychosis (e.g., social skill deficits, impoverished social networks, and negative symptoms).

Persistent social isolation reflects identity and social context but not maternal effects or early environment

Individuals who are well integrated into society have greater access to resources and tend to live longer. Why some individuals are socially isolated and others are not is therefore puzzling from an evolutionary perspective. Answering this question requires establishing the mix of intrinsic and contextual factors that contribute to social isolation. Using social network data spanning up to half of the median adult lifespan in a gregarious primate, we found that some measures of social isolation were modestly repeatable within individuals, consistent with a trait. By contrast, social isolation was not explained by the identity of an animal's mother or the group into which it was born. Nevertheless, age, sex and social status each played a role, as did kin dynamics and familiarity. Females with fewer close relatives were more isolated, and the more time males spent in a new group the less isolated they became, independent of their social status. These results show that social isolation results from a combination of intrinsic and environmental factors. From an evolutionary perspective, these findings suggest that social isolation could be adaptive in some contexts and partly maintained by selection.

BDNF Val66Met polymorphism modulates the effect of loneliness on white matter microstructure in young adults

Loneliness is a common experience. Susceptibility to loneliness is a stable trait and is heritable. Previous studies have suggested that loneliness may impact regional gray matter density and brain activation to social stimuli, but its relation to white matter structure and how it may interact with genetic factors remains unclear. In this study, we investigated whether and how a common polymorphism (Val66Met) in the brain-derived neurotrophic factor gene modulated the association between loneliness and white matter microstructure in 162 young adults. The tract-based spatial statistics analyses revealed that the relationships between loneliness and white matter microstructures were significantly different between Val/Met heterozygotes and Val/Val homozygotes. Specifically, loneliness was significantly correlated with reduced fractional anisotropy and increased radial diffusivity in widespread white matter fibers within Val/Met heterozygotes. It was also significantly correlated with increased radial diffusivity in Met/Met genotypes but showed no significant association with white matter measures in Val/Val genotypes. Furthermore, the associations between loneliness and fractional anisotropy (or radial diffusivity) in Val/Met heterozygotes turned out to be global effects. These results provide evidence that loneliness may interact with the BDNF Val66Met polymorphism to shape the microstructures of white matter, and the Val/Met heterozygotes may be more susceptible to social environment.

Differential transcriptome expression in human nucleus accumbens as a function of loneliness

Loneliness is associated with impaired mental and physical health. Studies of lonely individuals reported differential expression of inflammatory genes in peripheral leukocytes and diminished activation in brain reward regions such as nucleus accumbens, but could not address gene expression in the human brain. Here, we examined genome-wide RNA expression in post-mortem nucleus accumbens from donors (N=26) with known loneliness measures. Loneliness was associated with 1710 differentially expressed transcripts and genes from 1599 genes (DEGs; false discovery rate P<0.05, fold change ⩾|2|, controlling for confounds) previously associated with behavioral processes, neurological disease, psychological disorders, cancer, organismal injury and skeletal and muscular disorders, as well as networks of upstream RNA regulators. Furthermore, a number of DEGs were associated with Alzheimer's disease (AD) genes (that was correlated with loneliness in this sample, although gene expression analyses controlled for AD diagnosis). These results identify novel targets for future mechanistic studies of gene networks in nucleus accumbens and gene regulatory mechanisms across a variety of diseases exacerbated by loneliness.

The discrepancy between social isolation and loneliness as a clinically meaningful metric: findings from the Irish and English longitudinal studies of ageing (TILDA and ELSA)

OBJECTIVE

Scant evidence is available on the discordance between loneliness and social isolation among older adults. We aimed to investigate this discordance and any health implications that it may have.

METHOD

Using nationally representative datasets from ageing cohorts in Ireland (TILDA) and England (ELSA), we created a metric of discordance between loneliness and social isolation, to which we refer as Social Asymmetry. This metric was the categorised difference between standardised scores on a scale of loneliness and a scale of social isolation, giving categories of: Concordantly Lonely and Isolated, Discordant: Robust to Loneliness, or Discordant: Susceptible to Loneliness. We used regression and multilevel modelling to identify potential relationships between Social Asymmetry and cognitive outcomes.

RESULTS

Social Asymmetry predicted cognitive outcomes cross-sectionally and at a two-year follow-up, such that Discordant: Robust to Loneliness individuals were superior performers, but we failed to find evidence for Social Asymmetry as a predictor of cognitive trajectory over time.

CONCLUSIONS

We present a new metric and preliminary evidence of a relationship with clinical outcomes. Further research validating this metric in different populations, and evaluating its relationship with other outcomes, is warranted. Copyright © 2016 John Wiley & Sons, Ltd.

Genome-Wide Association Study of Loneliness Demonstrates a Role for Common Variation

Loneliness is a complex biological trait that has been associated with numerous negative health outcomes. The measurement and environmental determinants of loneliness are well understood, but its genetic basis is not. Previous studies have estimated the heritability of loneliness between 37 and 55% using twins and family-based approaches, and have explored the role of specific candidate genes. We used genotypic and phenotypic data from 10 760 individuals aged ⩾50 years that were collected by the Health and Retirement Study (HRS) to perform the first genome-wide association study of loneliness. No associations reached genome-wide significance (p>5 × 10^-8). Furthermore, none of the previously published associations between variants within candidate genes (BDNF, OXTR, RORA, GRM8, CHRNA4, IL-1A, CRHR1, MTHFR, DRD2, APOE) and loneliness were replicated (p>0.05), despite our much larger sample size. We estimated the chip heritability of loneliness and examined coheritability between loneliness and several personality and psychiatric traits. Our estimates of chip heritability (14-27%) support a role for common genetic variation. We identified strong genetic correlations between loneliness, neuroticism, and a scale of 'depressive symptoms.' We also identified weaker evidence for coheritability with extraversion, schizophrenia, bipolar disorder, and major depressive disorder. We conclude that loneliness, as defined in this study, is a modestly heritable trait that has a highly polygenic genetic architecture. The coheritability between loneliness and neuroticism may reflect the role of negative affectivity that is common to both traits. Our results also reflect the value of studies that probe the common genetic basis of salutary social bonds and clinically defined psychiatric disorders.

Unraveling the Role of Loneliness in Depression: The Relationship Between Daily Life Experience and Behavior

OBJECTIVE

Focusing on temporal associations between momentary (or state) loneliness, appraisal of social company, and being alone in daily life may help elucidate mechanisms that contribute to the development of prolonged (or trait) loneliness and major depressive disorder (MDD). We aim to examine if (a) a self-reinforcing loop between loneliness, negative appraisals of social company, and being alone in daily life may contribute to trait loneliness; (b) this possible self-reinforcing loop may also contribute to the development of MDD, by testing differences in temporal relationships between these social elements in participants who did or did not develop MDD during follow-up; and (c) any of these social elements at baseline predicted a MDD at follow-up.

METHODS

A female general population sample (n = 417) participated in an experience sampling method (ESM) study. Time-lagged analyses between loneliness, appraisal of social company, and being alone were examined at baseline, and their associations with the development of MDD during 20 months follow-up were investigated.

RESULTS

State loneliness was followed by an increase in negative appraisals of social company and a higher frequency of being alone. Further, negative appraisals of social company were associated with a higher frequency of being alone afterward. Only the latter was significant in the transition to MDD group. Trait loneliness predicted MDD during follow-up.

CONCLUSIONS

Avoiding social contact after appraising company more negatively may contribute to the development of MDD.

Safeness and Treatment Mitigate the Effect of Loneliness on Satisfaction With Elderly Care

Maximizing satisfaction among the older persons is the goal of modern individualized elderly care and how to best achieve this is of relevance for people involved in planning and providing elderly care services.

PURPOSE OF THE STUDY

What predicts satisfaction with care among older persons can be conceived as a function of process (how care is performed) and the older person. Inspired by the long-standing person versus situation debate, the present research investigated the interplay between person- and process-related factors in predicting satisfaction with elderly care.

DESIGN AND METHODS

A nationwide sample was analyzed, based on a questionnaire with 95,000 individuals using elderly care services.

RESULTS

The results showed that person-related factors (i.e., anxiety, health, and loneliness) were significant predictors of satisfaction with care, although less strongly than process-related factors (i.e., treatment, safeness, and perceived staff and time availability). Among the person-related factors, loneliness was the strongest predictor of satisfaction among older persons in nursing homes. Interestingly, a path analysis revealed that safeness and treatment function as mediators in linking loneliness to satisfaction.

IMPLICATIONS

The results based on a large national sample demonstrate that the individual aging condition to a significant degree can be countered by a well-functioning care process, resulting in higher satisfaction with care among older persons.