Implicit attention to negative social, in contrast to nonsocial, words in the Stroop task differs between individuals high and low in loneliness: Evidence from event-related brain microstates

Increased threat learning after social isolation in human adolescents

In animal models, social isolation impacts threat responding and threat learning, especially during development. This study examined the effects of acute social isolation on threat learning in human adolescents using an experimental, within-participant design. Participants aged 16-19 years underwent a session of complete isolation and a separate session of isolation with virtual social interactions, counterbalanced between participants, as well as a baseline session. At baseline and following each isolation session, participants reported their psychological state and completed a threat learning task in which self-report ratings and physiological responses to learned threat and safety cues were measured. Threat learning increased after both isolation sessions in two ways. First, participants found the learned threat cue more anxiety-inducing and unpleasant after isolation compared with baseline. Second, during threat extinction, electrodermal activity was partially elevated after isolation compared with baseline. Further, the results suggested that isolation influenced threat learning through state loneliness. Threat learning is central to threat-related disorders including anxiety, phobias, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD), and our findings suggest that isolation and loneliness in adolescence might increase vulnerability to the emergence of these disorders through increased threat learning.

[Loneliness in times of global polycrises]

Global polycrises comprise the synchronous or consecutive occurrence of various crises, with no intervening phases of stability, e.g., coronavirus disease 2019 (COVID-19) pandemic, inflation, war and climate crisis. This poses challenges for both society as a whole and its individual members. Polycrises are associated with enormous psychological stress, especially for vulnerable groups. Polycrises also impair social interaction, which can trigger or intensify subjectively stressful loneliness. The aim of this narrative review is to show how loneliness affects social behavior in times of global polycrises and what the consequences are. Loneliness is associated with both mental and physical morbidity and mortality as well as being a significant barrier to recovery. Studies have shown that there is a mutual detrimental influence between mental illness and loneliness. The social behavior of chronically lonely people is characterized by a negative cognitive bias, hypervigilance in the social context and a dysregulated oxytocin system. Furthermore, the quality and quantity of these relationships are significantly impaired. The social consequences of loneliness are, for example, a decrease in social engagement and low voting participation. The phenomenon of loneliness clearly shows that crises can exacerbate latent problems and bring them to the surface; however, crises should also be seen as an opportunity to openly and constructively address shame-laden topics such as loneliness in public discourse and in psychotherapeutic settings.

Ambiguity potentiates effects of loneliness on feelings of rejection

For social species, having strong and high-quality social relationships is an important safety cue. Loneliness occurs when an individual perceives they have insufficient relationships resulting in feelings of lack of safety. States of perceived unsafety are linked to an increased tendency to construe ambiguous information - information lacking a unique clear interpretation - as threatening. Here, we explore whether the ambiguity of social cues of interpersonal rejection moderates effects of loneliness on feelings of rejection while undergoing social exclusion. Data were collected in 2021; 144 adults completed a progressive social exclusion paradigm where they were randomly assigned to be equally included, excluded, or over-included. Social exclusion/inclusion cues became more pronounced over the course of multiple rounds of a ball-tossing game (Cyberball) resulting in a scenario where ambiguity was highest in earlier rounds and decreased over time. Participants reported feelings of loneliness prior to the task and feelings of rejection throughout the task. Results demonstrated that higher loneliness predicted increased feelings of rejection regardless of exclusion condition. Notably, this positive relationship was strongest during earlier rounds when social cues were most ambiguous. These findings contribute to our understanding of how loneliness modulates social perception to enable organisms to adequately adapt to changing circumstances.

A translational neuroscience perspective on loneliness: Narrative review focusing on social interaction, illness and oxytocin

This review addresses key findings on loneliness from the social, neurobiological and clinical fields. From a translational perspective, results from studies in humans and animals are included, with a focus on social interaction, mental and physical illness and the role of oxytocin in loneliness. In terms of social interactions, lonely individuals tend to exhibit a range of abnormal behaviors based on dysfunctional social cognitions that make it difficult for them to form meaningful relationships. Neurobiologically, a link has been established between loneliness and the hypothalamic peptide hormone oxytocin. Since social interactions and especially social touch regulate oxytocin signaling, lonely individuals may have an oxytocin imbalance, which in turn affects their health and well-being. Clinically, loneliness is a predictor of physical and mental illness and leads to increased morbidity and mortality. There is evidence that psychopathology is both a cause and a consequence of loneliness. The final section of this review summarizes the findings from social, neurobiological and clinical perspectives to present a new model of the complex construct of loneliness.

EEG Microstates in Social and Affective Neuroscience

Social interactions require both the rapid processing of multifaceted socio-affective signals (e.g., eye gaze, facial expressions, gestures) and their integration with evaluations, social knowledge, and expectations. Researchers interested in understanding complex social cognition and behavior face a "black box" problem: What are the underlying mental processes rapidly occurring between perception and action and why are there such vast individual differences? In this review, we promote electroencephalography (EEG) microstates as a powerful tool for both examining socio-affective states (e.g., processing whether someone is in need in a given situation) and identifying the sources of heterogeneity in socio-affective traits (e.g., general willingness to help others). EEG microstates are identified by analyzing scalp field maps (i.e., the distribution of the electrical field on the scalp) over time. This data-driven, reference-independent approach allows for identifying, timing, sequencing, and quantifying the activation of large-scale brain networks relevant to our socio-affective mind. In light of these benefits, EEG microstates should become an indispensable part of the methodological toolkit of laboratories working in the field of social and affective neuroscience.

Loneliness in the Daily Lives of People With Mood and Psychotic Disorders

BACKGROUND AND HYPOTHESIS

Loneliness, the subjective experience of feeling alone, is associated with physical and psychological impairments. While there is an extensive literature linking loneliness to psychopathology, limited work has examined loneliness in daily life in those with serious mental illness. We hypothesized that trait and momentary loneliness would be transdiagnostic and relate to symptoms and measures of daily functioning.

STUDY DESIGN

The current study utilized ecological momentary assessment and passive sensing to examine loneliness in those with schizophrenia (N = 59), bipolar disorder (N = 61), unipolar depression (N = 60), remitted unipolar depression (N = 51), and nonclinical comparisons (N = 82) to examine relationships of both trait and momentary loneliness to symptoms and social functioning in daily life.

STUDY RESULTS

Findings suggest that both trait and momentary loneliness are higher in those with psychopathology (F(4,284) = 28.00, P < .001, ηp2 = 0.27), and that loneliness significantly relates to social functioning beyond negative symptoms and depression (β = -0.44, t = 6.40, P < .001). Furthermore, passive sensing measures showed that greater movement (β = -0.56, t = -3.29, P = .02) and phone calls (β = -0.22, t = 12.79, P = .04), but not text messaging, were specifically related to decreased loneliness in daily life. Individuals higher in trait loneliness show stronger relationships between momentary loneliness and social context and emotions in everyday life.

CONCLUSIONS

These findings provide further evidence pointing to the importance of loneliness transdiagnostically and its strong relation to social functioning. Furthermore, we show that passive sensing technology can be used to measure behaviors related to loneliness in daily life that may point to potential treatment implications or early detection markers of loneliness.

A preliminary study on the neurocognitive deficits associated with loneliness in young adults

The experience of loneliness is universal and may have an adverse effect on neurocognitive functioning even at a younger age. Using a comprehensive neurocognitive functioning test (NCFT) battery, we examined the possible negative effects of loneliness on neurocognitive functioning in young adults. The high-loneliness and low-loneliness groups were screened using the UCLA Loneliness Scale v. 3, and measures pertaining to the domains of intelligence, attention, memory, executive function, and psychomotor functioning were tested and compared. As depression and anxiety were significantly higher in the high-loneliness group, an analysis of covariance was conducted. As a result, the high-loneliness group showed significantly poor performance on measures of executive function and attention prior to controlling for depression and anxiety, and executive function retained its significance even after controlling for these variables. Additional analysis showed that depression and anxiety did not significantly mediate the relationship between loneliness and neurocognitive functioning. Such results suggest that loneliness is likely to negatively affect executive functioning and attention in early adulthood and then progressively spread to other domains of cognitive functioning, as reported in the older adult population. The limitations and implications of the present study were considered and addressed.

Social Isolation, Brain Food Cue Processing, Eating Behaviors, and Mental Health Symptoms

Importance

Perceived social isolation is associated with negative health outcomes, including increased risk for altered eating behaviors, obesity, and psychological symptoms. However, the underlying neural mechanisms of these pathways are unknown.

Objective

To investigate the association of perceived social isolation with brain reactivity to food cues, altered eating behaviors, obesity, and mental health symptoms.

Design, Setting, and Participants

This cross-sectional, single-center study recruited healthy, premenopausal female participants from the Los Angeles, California, community from September 7, 2021, through February 27, 2023.

Exposure

Participants underwent functional magnetic resonance imaging while performing a food cue viewing task.

Main Outcomes and Measures

The main outcomes included brain reactivity to food cues, body composition, self-reported eating behaviors (food cravings, reward-based eating, food addiction, and maladaptive eating behaviors), and mental health symptoms (anxiety, depression, positive and negative affect, and psychological resilience).

Results

The study included 93 participants (mean [SD] age, 25.38 [7.07] years). Participants with higher perceived social isolation reported higher fat mass percentage, lower diet quality, increased maladaptive eating behaviors (cravings, reward-based eating, uncontrolled eating, and food addiction), and poor mental health (anxiety, depression, and psychological resilience). In whole-brain comparisons, the higher social isolation group showed altered brain reactivity to food cues in regions of the default mode, executive control, and visual attention networks. Isolation-related neural changes in response to sweet foods correlated with various altered eating behaviors and psychological symptoms. These altered brain responses mediated the connection between social isolation and maladaptive eating behaviors (β for indirect effect, 0.111; 95% CI, 0.013-0.210; P = .03), increased body fat composition (β, -0.141; 95% CI, -0.260 to -0.021; P = .02), and diminished positive affect (β, -0.089; 95% CI, -0.188 to 0.011; P = .09).

Conclusions and Relevance

These findings suggest that social isolation is associated with altered neural reactivity to food cues within specific brain regions responsible for processing internal appetite-related states and compromised executive control and attentional bias and motivation toward external food cues. These neural responses toward specific foods were associated with an increased risk for higher body fat composition, worsened maladaptive eating behaviors, and compromised mental health. These findings underscore the need for holistic mind-body-directed interventions that may mitigate the adverse health consequences of social isolation.

Can we dissociate hypervigilance to social threats from altered perceptual decision-making processes in lonely individuals? An exploration with Drift Diffusion Modeling and event-related potentials

It has been hypothesized that lonely individuals demonstrate hypervigilance toward social threats. However, recent studies have raised doubts about the reliability of tasks commonly used to measure attentional biases toward threats. Two alternative approaches have been suggested to overcome the limitations of traditional analysis of attentional bias. First, the neurophysiological indicators of orienting to threats were shown to have superior psychometric characteristics compared to overt measures of behavioral performance. The second approach involves utilizing computational modeling to isolate latent components corresponding to specific cognitive mechanisms from observable data. To test the usefulness of these approaches in loneliness research, we analyzed behavioral and electroencephalographic (EEG) data from 26 lonely and 26 non-lonely participants who performed a dot-probe task using a computational modeling approach. We applied the Drift Diffusion Model (DDM) and extracted N2pc-an event-related potential that serves as an indicator of spatial attention. No evidence for social threat hypervigilance has been found in DDM parameters nor in N2pc characteristics in the current study. However, we did observe decreased drift rate and increased variability in drift rate between trials within the lonely group, indicating reduced efficiency in perceptual decision-making among lonely individuals. These effects were not detected using standard behavioral measures used in the dot-probe paradigm. Given that DDM indicators were sensitive to differences in perceptual discrimination between the two groups, even when no overt differences were found in standard behavioral measures, it may be postulated that computational approaches offer a more comprehensive understanding of cognitive processes.

Association of loneliness and grey matter volume in the dorsolateral prefrontal cortex: the mediating role of interpersonal self-support traits

As a social and public health concern, loneliness is associated with an abundance of negative life outcomes such as depressive symptomatology, mortality, and sleep disturbance. Nevertheless, the neural basis underlying loneliness remains elusive; in addition, previous neuroimaging studies about loneliness mainly focused on the elderly and were limited by small sample sizes. Here, utilizing the voxel-based morphometry (VBM) approach via structural magnetic resonance imaging, we investigated the association between brain GMV and loneliness in 462 young adults (67.7% females, age = 18.59 ± 1.14 years). Results from whole-brain VBM analyses revealed that individuals with higher loneliness tended to have greater GMV in the right dorsolateral prefrontal cortex (DLPFC), which was thought to be associated with emotional regulation deficits and executive dysfunction. Importantly, the GMV-based predictive models (a machine-learning method) demonstrated that the correlation between loneliness and GMV in the DLPFC was robust. Further, interpersonal self-support traits (ISS), a Chinese indigenous personality construct and pivotal personality factor for resisting negative life outcomes, mediated the relationship between the GMV in the right DLPFC and loneliness. Taken together, the present study reveals that the GMV in right DLPFC acts as an underlying neurostructural correlate of loneliness in the healthy brain, and further provides a brain-personality-symptom pathway for protection against loneliness in which GMV of DLPFC affects loneliness through ISS traits. Future intervention procedures aiming to decrease loneliness and enhance mental health levels among young adults should be developed through improving interpersonal relationships such as social skills training.

Do loneliness and social exclusion breed paranoia? An experience sampling investigation across the psychosis continuum

Background

The role of loneliness and social exclusion in the development of paranoia is largely unexplored. Negative affect may mediate potential associations between these factors. We investigated the temporal relationships of daily-life loneliness, felt social exclusion, negative affect, and paranoia across the psychosis continuum.

Method

Seventy-five participants, including 29 individuals with a diagnosis of non-affective psychosis, 20 first-degree relatives, and 26 controls used an Experience Sampling Method (ESM) app to capture the fluctuations in loneliness, feelings of social exclusion, paranoia, and negative affect across a 1-week period. Data were analysed with multilevel regression analyses.

Results

In all groups, loneliness and feelings of social exclusion were independent predictors of paranoia over time (b = 0.05, p < .001 and b = 0.04, p < .05, respectively). Negative affect predicted paranoia (b = 0.17, p < .001) and partially mediated the associations between loneliness, social exclusion, and paranoia. It also predicted loneliness (b = 0.15, p < .0001), but not social exclusion (b = 0.04, p = .21) over time. Paranoia predicted social exclusion over time, with more pronounced effects in controls (b = 0.43) than patients (b = 0.19; relatives: b = 0.17); but not loneliness (b = 0.08, p = .16).

Conclusion

Paranoia and negative affect worsen in all groups following feelings of loneliness and social exclusion. This highlights the importance of a sense of belonging and being included for mental well-being. Loneliness, feeling socially excluded, and negative affect were independent predictors of paranoid thinking, suggesting they represent useful targets in its treatment.

Cross-Sectional and Prospective Relationships Between Neuroticism and Depressive Symptoms Among College Students: The Mediating Role of Loneliness

High levels of neuroticism are associated with an increased risk of depression. The mechanisms for this association are still unclear. This study investigated loneliness, a pervasive negative human emotion linked to depressive symptoms, as a potential mediator. Data were collected from 739 college students (71.6% females; mean age = 18.47, SD = .87) at two times points through 3 years. Self-report questionnaires were administered to assess neuroticism, loneliness, and depressive symptoms. Cross-sectional analyses of the baseline data suggested that loneliness mediates the association between neuroticism and depressive symptoms. Prospective analyses with two-wave data further prove that baseline neuroticism can predict the changes in depressive symptoms, and changes in loneliness sequentially mediated this association. These findings suggest a possibility of developing interventions for loneliness to interrupt the association between neuroticism and poorer mental health outcomes among college students.

Age differences in functional brain networks associated with loneliness and empathy

Loneliness is associated with differences in resting-state functional connectivity (RSFC) within and between large-scale networks in early- and middle-aged adult cohorts. However, age-related changes in associations between sociality and brain function into late adulthood are not well understood. Here, we examined age differences in the association between two dimensions of sociality-loneliness and empathic responding-and RSFC of the cerebral cortex. Self-report measures of loneliness and empathy were inversely related across the entire sample of younger (mean age = 22.6y, n = 128) and older (mean age = 69.0y, n = 92) adults. Using multivariate analyses of multi-echo fMRI RSFC, we identified distinct functional connectivity patterns for individual and age group differences associated with loneliness and empathic responding. Loneliness in young and empathy in both age groups was related to greater visual network integration with association networks (e.g., default, fronto-parietal control). In contrast, loneliness was positively related to within- and between-network integration of association networks for older adults. These results extend our previous findings in early- and middle-aged cohorts, demonstrating that brain systems associated with loneliness, as well as empathy, differ in older age. Further, the findings suggest that these two aspects of social experience engage different neurocognitive processes across human life-span development.

Disgust as a transdiagnostic index of mental illness: A narrative review of clinical populations

Disgust is a basic emotion of rejection, providing an ancestral defensive mechanism against illness. Based on research that documents altered experiences of disgust across several psychopathological conditions, we conducted a narrative review to address the hypothesis that altered disgust may serve as a transdiagnostic index of mental illness. Our synthesis of the literature from past decades suggests that, compared to healthy populations, patients with mental disorders exhibit abnormal processing of disgust in at least one of the analyzed dimensions. We also outline evidence of alterations in brain areas relevant to disgust processing, such as the insula and the interconnected limbic network. Overall, we provide preliminary support for the hypothesis that altered disgust processing may serve as a transdiagnostic index of mental illness.

Social contacts and loneliness affect the own age bias for emotional faces

Individuals are better at recognizing faces of their own age group (Own Age Bias) but it is unclear whether this bias occurs also for emotional faces and to what extent is affected by loneliness. Young individuals (N = 235) completed an age categorization task on faces of young and old individuals showing neutral, happy, and angry expressions. After a filler task, they categorized as seen or novel the original set of faces intermixed with a new set. Findings showed an Own Age Bias for novel young faces but no evidence that emotion eliminates it. Recognition accuracy was better for emotional faces, but the two factors did not interact. Importantly, low loneliness was linked to an Own Age Bias for novel happy faces. These findings are discussed in the context of current theoretical accounts of the Own Age Bias and of the effects of loneliness on attention and memory.

Anxiety disrupts performance monitoring: integrating behavioral, event-related potential, EEG microstate, and sLORETA evidence

Anxiety impacts performance monitoring, though theory and past research are split on how and for whom. However, past research has often examined either trait anxiety in isolation or task-dependent state anxiety and has indexed event-related potential components, such as the error-related negativity or post-error positivity (Pe), calculated at a single node during a limited window of time. We introduced 2 key novelties to this electroencephalography research to examine the link between anxiety and performance monitoring: (i) we manipulated antecedent, task-independent, state anxiety to better establish the causal effect; (ii) we conducted moderation analyses to determine how state and trait anxiety interact to impact performance monitoring processes. Additionally, we extended upon previous work by using a microstate analysis approach to isolate and sequence the neural networks and rapid mental processes in response to error commission. Results showed that state anxiety disrupts response accuracy in the Stroop task and error-related neural processes, primarily during a Pe-related microstate. Source localization shows that this disruption involves reduced activation in the dorsal anterior cingulate cortex and compensatory activation in the right lateral prefrontal cortex, particularly among people high in trait anxiety. We conclude that antecedent anxiety is largely disruptive to performance monitoring.

Frontal Alpha Asymmetry and Negative Mood: A Cross-Sectional Study in Older and Younger Adults

Frontal alpha asymmetry (FAA) has been associated with emotional processing and affective psychopathology. Negative and withdrawal stimuli and behaviors have been related to high levels of right cortical activity, while positive and approach stimuli and behaviors have been related to increased left cortical activity. Inconsistent results in terms of depressive and anxious symptoms and their relationship to FAA have been previously observed, especially at older ages. Additionally, no studies to date have evaluated whether loneliness, a negative feeling, is related to FAA. Therefore, this study aimed (i) to compare FAA between younger and older adults and (ii) to investigate the possible relationships between loneliness, depressive and anxious symptomatology with FAA in young and older adults. Resting electroencephalogram recordings of 39 older (Mage = 70.51, SD = 7.12) and 57 younger adults (Mage = 22.54, SD = 3.72) were analyzed. Results showed greater left than right cortical activity for both groups and higher FAA for older than younger adults. FAA was not predicted by loneliness, depressive or anxious symptomatology as shown by regression analyses. Findings bring clarity about FAA patterns at different ages and open the discussion about the relationship between negative emotional processing and frontal cortical imbalances, especially at older ages.

Prevalence and Risk Factors of Psychiatric Symptoms Among Older People in England During the COVID-19 Pandemic: a Latent Class Analysis

The COVID-19 pandemic has affected mental health and social connections. Older people may be disproportionately affected, placing them at increased risk for complex mental ill-health outcomes and quality of life undermined by anxiety and depression. Understanding gender differences in the determinants of anxiety and depression symptoms is crucial to policy and practice. This study aims to examine gender-specific symptom subtypes (and subthreshold symptoms) in an older English population sampled during the COVID period, in relation to their socio-demographic, social, and health circumstances. The sample comprises all individuals aged 50 years or older and included in the English Longitudinal Study of Ageing COVID-19 sub-study conducted during June-July 2020. Latent class analysis (LCA) defined indicative sample subgroups of clinically relevant anxiety and depression. Multinomial logistic regression assessed associations between socio-demographic characteristics, health and social care indicators, loneliness, and pre-pandemic mental ill-health. LCA derived three classes of self-reported depression and anxiety: for females (1) comorbid depression and anxiety (19.9% of the sample), (2) depression and subthreshold anxiety (31.6%), and (3) no or low symptoms of depression and anxiety (48.5%), and for males (1) comorbid depression and anxiety (12.8%), (2) subthreshold anxiety and depression (29.6%), and (3) no or low depression and anxiety (57.6%). Multinomial logistic regression analyses indicate that compared to those with low/no mental health symptoms, severity of pandemic-era mental ill-health was positively associated with pre-pandemic mental health levels, worry over finances, having access to essentials, loneliness, and access to health and social care services. Findings support the persistence of comorbidity of both depression and anxiety in the pandemic period. Results may inform government health strategy on interventions to prevent social isolation and mitigate the effects of the pandemic on deteriorating mental health in older people who may be more susceptible.

Neurobiology of Loneliness, Isolation, and Loss: Integrating Human and Animal Perspectives

In social species such as humans, non-human primates, and even many rodent species, social interaction and the maintenance of social bonds are necessary for mental and physical health and wellbeing. In humans, perceived isolation, or loneliness, is not only characterized by physical isolation from peers or loved ones, but also involves negative perceptions about social interactions and connectedness that reinforce the feelings of isolation and anxiety. As a complex behavioral state, it is no surprise that loneliness and isolation are associated with dysfunction within the ventral striatum and the limbic system - brain regions that regulate motivation and stress responsiveness, respectively. Accompanying these neural changes are physiological symptoms such as increased plasma and urinary cortisol levels and an increase in stress responsivity. Although studies using animal models are not perfectly analogous to the uniquely human state of loneliness, studies on the effects of social isolation in animals have observed similar physiological symptoms such as increased corticosterone, the rodent analog to human cortisol, and also display altered motivation, increased stress responsiveness, and dysregulation of the mesocortical dopamine and limbic systems. This review will discuss behavioral and neuropsychological components of loneliness in humans, social isolation in rodent models, and the neurochemical regulators of these behavioral phenotypes with a neuroanatomical focus on the corticostriatal and limbic systems. We will also discuss social loss as a unique form of social isolation, and the consequences of bond disruption on stress-related behavior and neurophysiology.

Loneliness and cardiovascular reactivity to acute stress in older adults

Loneliness has been linked to cardiovascular health outcomes in older adulthood. One proposed mechanism by which loneliness influences cardiovascular health is through atypical cardiovascular reactivity (CVR) to stress. This study is an examination of loneliness and CVR in older adults, comparing associations across two stressors and two commonly used measures of loneliness, with a particular focus on underlying hemodynamic variables including cardiac output, total peripheral resistance, and ejection time (EJT). Eighty older adults, ranging in age from 55 to 88 years (M = 68.93, SD = 8.28), completed two versions of the UCLA loneliness scale (a 20‐item and a briefer, three‐item) and took part in a laboratory stress‐testing procedure which included a mental arithmetic challenge and a public speaking task. Cardiovascular activity was monitored continuously throughout. For the 20‐item version of the UCLA loneliness scale, loneliness was not significantly related to CVR, and was only significantly associated with lower levels of overall EJT. For the three‐item version of the UCLA, no associations withstood adjustment for multiple testing. Loneliness was not reliably associated with CVR. Further, although greater loneliness was related to lower levels of overall EJT, this was only observed for the 20‐item scale. The findings do not strongly provide support for reactivity to acute stress as a pathway linking loneliness to disease outcomes, and highlight key methodological issues related to the assessment of loneliness‐reactivity associations for future.

This article provides an examination of associations between loneliness and cardiovascular reactivity (CVR) to acute stress in a sample of older adults. The findings do not provide support for a reliable association between loneliness and CVR in older adults. This article highlights methodological issues that are important to consider for future in this research area.

Touched by loneliness-how loneliness impacts the response to observed human touch: a tDCS study

Lonely people often crave connectedness. However, they may also experience their environment as threatening, entering a self-preserving state that perpetuates loneliness. Research shows conflicting evidence about their response to positive social cues, and little is known about their experience of observed human touch. The right inferior frontal gyrus (rIFG) is part of an observation-execution network implicated in observed touch perception. Correlative studies also point to rIFG's involvement in loneliness. We examined the causal effect of rIFG anodal transcranial direct current stimulation on high- and low-loneliness individuals observing human touch. In a cross-over design study, 40 participants watched pictures of humans or objects touching or not touching during anodal and sham stimulations. Participants indicated whether pictures contained humans or objects, and their reaction time was measured. Results show that the reaction time of low-loneliness individuals to observed human touch was significantly slower during anodal stimulation compared to high-loneliness individuals, possibly due to them being more emotionally distracted by it. Lonely individuals also reported less liking of touch. Our findings support the notion that lonely individuals are not drawn to positive social cues. This may help explain the perpetuation of loneliness, despite social opportunities that could be available to lonely people.

Choking under pressure: Does it get easier with age? How loneliness affects social monitoring across the life span

Previous experimental work showed that young adults reporting loneliness performed less well on emotion recognition tasks (Diagnostic Analysis of Nonverbal Accuracy [DANVA-2]) if they were framed as indicators of social aptitude, but not when the same tasks were framed as indexing academic aptitude. Such findings suggested that undergraduates reporting loneliness possessed the social monitoring skills necessary to read the emotions underlying others’ facial expressions, but that they choked under social pressure. It has also been found that undergraduates reporting loneliness have better recall for both positive and negative social information than their non-lonely counterparts. Whether those effects are evident across different age groups has not been examined. Using data from the British Broadcasting Corporation (BBC) Loneliness Experiment that included participants aged 16–99 years (N = 54,060), we (i) test for replication in a larger worldwide sample and (ii) extend those linear model analyses to other age groups. We found only effects for participants aged 25–34 years: In this age group, loneliness was associated with increased recall of negative individual information, and with choking under social pressure during the emotion recognition task; those effects were small. We did not find any such effects among participants in other age groups. Our findings suggest that different cognitive processes may be associated with loneliness in different age groups, highlighting the importance of life-course approaches in this area.

Affective Neuroscience of Loneliness: Potential Mechanisms underlying the Association between Perceived Social Isolation, Health, and Well-Being

Loneliness, or the subjective feeling of social isolation, is an important social determinant of health. Loneliness is associated with poor physical health, including higher rates of cardiovascular disease and dementia, faster cognitive decline, and increased risk of mortality, as well as disruptions in mental health, including higher levels of depression, anxiety, and negative affect. Theoretical accounts suggest loneliness is a complex cognitive and emotional state characterized by increased levels of inflammation and affective disruptions. This review examines affective neuroscience research on social isolation in animals and loneliness in humans to better understand the relationship between perceptions of social isolation and the brain. Loneliness associated increases in inflammation and neural changes consistent with increased sensitivity to social threat and disrupted emotion regulation suggest interventions targeting maladaptive social cognitions may be especially effective. Work in animal models suggests the neural changes associated with social isolation may be reversible. Therefore, ameliorating loneliness may be an actionable social determinant of health target. However, more research is needed to understand how loneliness impacts healthy aging, explore the role of inflammation as a potential mechanism in humans, and determine the best time to deliver interventions to improve physical health, mental health, and well-being across a diverse array of populations.

Individual Differences in Cerebral Perfusion as a Function of Age and Loneliness

Loneliness is defined as the subjective feeling that one's social needs are not satisfied by both quantity and quality of one's social relationships. Loneliness has been linked to a broad range of adverse physical and mental health consequences. There is an interest in identifying the neural and molecular processes by which loneliness adversely affects health. Prior imaging studies reported divergent networks involved in cognitive, emotional, and social processes associated with loneliness. Although loneliness is common among both younger and older adults, it is experienced differently across the lifespan and has different antecedents and consequences. The current study measured regional cerebral blood flow (CBF) using pulsed arterial spin labeling imaging. Forty-five older (M_age = 63.4) and forty-four younger adults (M_age = 20.9) with comparable degrees of loneliness were included. Whole-brain voxel-wise analysis revealed a main effect of age (in superior temporal and supramarginal gyri), but no main effect of loneliness. Furthermore, the age effect was only observed among people who reported higher level of loneliness. These regions have previously been implicated in social- and attention-related functions. The moderation of loneliness on age and regional CBF suggests that younger and older individuals present differential neural manifestations in response to loneliness, even with comparable levels of loneliness.

Conditional Process Modeling of the Relationship Among Self-Reliance, Loneliness, and Depressive Symptoms, and the Moderating Effect of Feeling Understood

ABSTRACT

Self-reliance features as one of the notable male norms espoused by traditional masculine socialization. Strict adherence to a self-reliant attitude has been found to confer risk for depression and suicidality among men. Yet, little research has investigated the factors that may contribute to self-reliance having a negative impact for men. Using data from a large sample of Canadian men (N = 530), the present study examined the association between self-reliance and depression, while also assessing the roles of loneliness and not feeling understood as contributing factors in this process. Findings indicated that the moderated mediation model was significant, pointing to loneliness as a significant mediator in the association between self-reliance and depression. Furthermore, the findings revealed that not feeling understood moderated the relationship between self-reliance and loneliness, indicating that this association applies mainly to those men who do not feel understood by at least one important person in their life.

A meta-analysis of loneliness and use of primary health care

Loneliness is a growing public health concern that is associated with a range of negative health outcomes. The extent to which loneliness may also be associated with greater use of primary health care remains unclear. The present meta-analysis aimed to address this gap by quantifying research on the association of loneliness to primary health care use. The database searches yielded 23 eligible studies with 25 effects, total N = 113,639. A random effects meta-analysis revealed a small positive average effect size (r_avg = .094; 95% CI [.07, .12])between loneliness and the use of primary care that increased in magnitude as the proportion of females in the samples increased. Studies that used objective measures of primary care use yielded effects that were significantly larger than those using self-report measures. The effects were robust to differences in age and type of health-care systems, and the type of loneliness scale (single versus multi-item). The findings from this first comprehensive meta-analysis of the association of loneliness with use of primary care indicate that people who experience loneliness make a greater number of visits to primary-care practitioners. This evidence highlights the practical impact of loneliness on health-care use when viewed at the population level.

Neurobiology of loneliness: a systematic review

Loneliness is associated with increased morbidity and mortality. Deeper understanding of neurobiological mechanisms underlying loneliness is needed to identify potential intervention targets. We did not find any systematic review of neurobiology of loneliness. Using MEDLINE and PsycINFO online databases, we conducted a search for peer-reviewed publications examining loneliness and neurobiology. We identified 41 studies (n = 16,771 participants) that had employed various methods including computer tomography (CT), structural magnetic resonance imaging (MRI), functional MRI (fMRI), electroencephalography (EEG), diffusion tensor imaging (DTI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and post-mortem brain tissue RNA analysis or pathological analysis. Our synthesis of the published findings shows abnormal structure (gray matter volume or white matter integrity) and/or activity (response to pleasant versus stressful images in social versus nonsocial contexts) in the prefrontal cortex (especially medial and dorsolateral), insula (particularly anterior), amygdala, hippocampus, and posterior superior temporal cortex. The findings related to ventral striatum and cerebellum were mixed. fMRI studies reported links between loneliness and differential activation of attentional networks, visual networks, and default mode network. Loneliness was also related to biological markers associated with Alzheimer's disease (e.g., amyloid and tau burden). Although the published investigations have limitations, this review suggests relationships of loneliness with altered structure and function in specific brain regions and networks. We found a notable overlap in the regions involved in loneliness and compassion, the two personality traits that are inversely correlated in previous studies. We have offered recommendations for future research studies of neurobiology of loneliness.

Opposing Association of Situational and Chronic Loneliness with Interpersonal Distance

Loneliness is a prevalent condition with adverse effects on physical and mental health. Evolutionary theories suggest it evolved to drive people to reconnect. However, chronic loneliness may result in a negative social bias and self-preservation behaviors, paradoxically driving individuals away from social interactions. Lonely people often feel they are not close to anyone; however, little is known about their interpersonal distance preferences. During COVID-19, many experienced situational loneliness related to actual social isolation. Therefore, there was a unique opportunity to examine both chronic and situational (COVID-19-related) loneliness. In the present study, 479 participants completed an online task that experimentally assessed interpersonal distance preferences in four conditions-passively being approached by a friend or a stranger, and actively approaching a friend or a stranger. Results show that high chronic loneliness was related to a greater preferred distance across conditions. Intriguingly, by contrast, high COVID-19-related loneliness was related to a smaller preferred distance across conditions. These findings provide further support for the evolutionary theory of loneliness: situational loneliness indeed seems to drive people towards reconnection, while chronic loneliness seems to drive people away from it. Implications for the amelioration of chronic loneliness are discussed based on these findings.

Cognitive and Neural Correlates of Loneliness and Wisdom during Emotional Bias

Loneliness and wisdom have opposing impacts on health and well-being, yet their neuro-cognitive bases have never been simultaneously investigated. In this study of 147 healthy human subjects sampled across the adult lifespan, we simultaneously studied the cognitive and neural correlates of loneliness and wisdom in the context of an emotion bias task. Aligned with the social threat framework of loneliness, we found that loneliness was associated with reduced speed of processing when angry emotional stimuli were presented to bias cognition. In contrast, we found that wisdom was associated with greater speed of processing when happy emotions biased cognition. Source models of electroencephalographic data showed that loneliness was specifically associated with enhanced angry stimulus-driven theta activity in the left transverse temporal region of interest, which is located in the area of the temporoparietal junction (TPJ), while wisdom was specifically related to increased TPJ theta activity during happy stimulus processing. Additionally, enhanced attentiveness to threatening stimuli for lonelier individuals was observed as greater beta activity in left superior parietal cortex, while wisdom significantly related to enhanced happy stimulus-evoked alpha activity in the left insula. Our results demonstrate emotion-context driven modulations in cognitive neural circuits by loneliness versus wisdom.

Important Correlates of Purpose in Life Identified Through a Machine Learning Approach

OBJECTIVE

A wealth of evidence has linked purpose in life (PiL) to better mental and physical health and healthy aging. Here, the authors aimed to determine important correlates of PiL using a machine learning approach.

METHODS

Participants were recruited from retirement communities by the Rush Memory and Aging Project and assessed for childhood experience, adulthood sociodemographic factors (e.g., education, income, marital status), lifestyle and health behavior (e.g., cognitively stimulating activities, exercise, social activities, social network size), psychological factors (e.g., depression, loneliness, perceived discrimination, perceived social support), personality traits (e.g., PiL, harm avoidance), and medical conditions. Elastic Net was implemented to identify important correlates of PiL.

RESULTS

A total of 1,839 participants were included in our analysis. Among the 23 variables provided to Elastic Net, 10 were identified as important correlates of PiL. In order of decreasing effect size, factors associated with lower PiL were loneliness, harm avoidance, older age, and depressive symptoms, while those associated with greater PiL were perceived social support, more social activities, more years of education, higher income, intact late-life cognitive performance, and more middle-age cognitive activities.

CONCLUSION

Our findings identify potentially important modifiable factors as targets for intervention strategies to enhance PiL.

Expressive flexibility and anxiety

BACKGROUND

The ability to flexibly enhance and suppress emotional expressions plays an important role in emotion regulation and the fostering of social connections. Deficits in expressive flexibility have been linked with posttraumatic stress disorder and prolonged grief reactions. Previous studies have suggested that the ability to respond flexibly in the context of an immediate threat (a nonconscious prime) may be important. In this study we sought to extend this work by examining the impact of individual differences in anxiety on expressive flexibility.

METHODS

Eighty four participants with high and low trait anxiety viewed blocks of negative images with instructions to enhance or suppress emotional expressions. Across blocks one of three nonconscious primes (threat, safety, neutral) appeared before each image. Observers blind to the study's design rated participants' emotional expressiveness.

RESULTS

Repeated Measures Anova's showed that high trait anxiety was associated with lower levels in enhancement ability. Further, low trait anxiety was associated with less emotion in response to the threat prime irrespective of expressive instruction.

LIMITATIONS

This study was cross-sectional which precludes causal relationships. Participants were drawn from a student population and the generalizability to other populations will need to be established CONCLUSIONS: This study identified trait anxiety as factor that may contribute to expressive flexibility deficits. High trait anxiety is a feature of many clinical conditions. Strategies to target expressive flexibility may relevant to a range of anxiety related clinical conditions.

Peer network Status and Depressive Symptoms Among Early Adolescents: Testing the Mediating Effects of Metaperception and Loneliness

Previous research shows that deficits in social relationships increase the risk of depression. This study tests the hypothesis that among early adolescents, their status in their peer network (likeability/dislikeability) will be associated with depressive symptoms but only indirectly, through the subjective perception of this status (positive/negative metaperception) and loneliness (feeling of social isolation). Data were collected using sociometric methods and self-report scales from 388 students aged 12–13. Path analysis was applied to verify the hypothesized relationships between the study variables. The findings indicate that: (1) status in the peer network and its perception affect depressive symptoms only indirectly, through loneliness; (2) depressive symptoms depend directly on loneliness alone; (3) status in the peer network does not directly translate into loneliness—its effect is mediated by metaperception; (4) the negative dimension of the peer network status indirectly affects both loneliness and depressive symptoms more strongly than the positive one. The main limitation of the research is its cross-sectional design, which precludes definite conclusions about the direction of the relationships observed. The results obtained help to clarify the complex mechanisms through which objective status in the peer network, its subjective perception and feelings of loneliness contribute to the severity of depressive symptoms among early adolescents. On the practical side, the findings highlight the importance of developing and implementing interventions targeting both the objective and subjective aspects of social relations for the prevention of depression in this age group.

The default network of the human brain is associated with perceived social isolation

Humans survive and thrive through social exchange. Yet, social dependency also comes at a cost. Perceived social isolation, or loneliness, affects physical and mental health, cognitive performance, overall life expectancy, and increases vulnerability to Alzheimer's disease-related dementias. Despite severe consequences on behavior and health, the neural basis of loneliness remains elusive. Using the UK Biobank population imaging-genetics cohort (n = ~40,000, aged 40-69 years when recruited, mean age = 54.9), we test for signatures of loneliness in grey matter morphology, intrinsic functional coupling, and fiber tract microstructure. The loneliness-linked neurobiological profiles converge on a collection of brain regions known as the 'default network'. This higher associative network shows more consistent loneliness associations in grey matter volume than other cortical brain networks. Lonely individuals display stronger functional communication in the default network, and greater microstructural integrity of its fornix pathway. The findings fit with the possibility that the up-regulation of these neural circuits supports mentalizing, reminiscence and imagination to fill the social void.

Loneliness and depression dissociated on parietal-centered networks in cognitive and resting states

BACKGROUND

Perceived loneliness, an increasingly prevalent social issue, is closely associated with major depressive disorder (MDD). However, the neural mechanisms previously implicated in key cognitive and affective processes in loneliness and MDD still remain unclear. Such understanding is critical for delineating the psychobiological basis of the relationship between loneliness and MDD.

METHODS

We isolated the unique and interactive cognitive and neural substrates of loneliness and MDD among 27 MDD patients (mean age = 51.85 years, 20 females), and 25 matched healthy controls (HCs; mean age = 48.72 years, 19 females). We assessed participants' behavioral performance and neural regional and network functions on a Stroop color-word task, and their resting-state neural connectivity.

RESULTS

Behaviorally, we found greater incongruence-related accuracy cost in MDD patients, but reduced incongruence effect on reaction time in lonelier individuals. When performing the Stroop task, loneliness positively predicted prefrontal-anterior cingulate-parietal connectivity across all participants, whereas MDD patients showed a decrease in connectivity compared to controls. Furthermore, loneliness negatively predicted parietal and cerebellar activities in MDD patients, but positively predicted the same activities in HCs. During resting state, MDD patients showed reduced parietal-anterior cingulate connectivity, which again positively correlated with loneliness in this group.

CONCLUSIONS

We speculate the distinct neurocognitive profile of loneliness might indicate increase in both bottom-up attention and top-down executive control functions. However, the upregulated cognitive control processes in lonely individuals may eventually become exhausted, which may in turn predispose to MDD onset.

Increased pSTS activity and decreased pSTS-mPFC connectivity when processing negative social interactions

We have previously shown that activity and connectivity within and between the action observation and mentalizing brain systems reflect the degree of positive dimensions expressed by social interactions such as cooperativity and affectivity, respectively. Here we aim to extend this evidence by investigating the neural bases of processing negative dimensions of observed interactions, such as competition and affective conflict, possibly representing a benchmark for different pathological conditions. In this fMRI study 34 healthy participants were shown pictures depicting interactions characterized by two crossed dimensions, i.e. positively- vs. negatively- connotated social intentions mainly expressed in terms of motor acts vs. mental states, i.e. cooperative, competitive, affective and conflicting interactions. We confirmed the involvement of the action observation and mentalizing networks in processing intentions mainly expressed through motor acts (cooperative/competitive) vs. mental states (affective/conflicting), respectively. Results highlighted the selective role of the left pSTS/TPJ in decoding social interactions, even when compared with parallel actions by non-interacting individuals. Its right-hemispheric homologue displayed stronger responses to negative than positive social intentions, regardless of their motor/mental status, and decreased connectivity with the medial prefrontal cortex (mPFC) when processing negative interactions. The resulting mPFC downregulation by negative social scenes might reflect an adaptive response to socio-affective threats, via decreased mentalizing when facing negative social stimuli. This evidence on the brain mechanisms underlying the decoding of real complex interactions represents a baseline for assessing both the neural correlates of impaired social cognition, and the effects of rehabilitative treatments, in neuro-psychiatric diseases or borderline conditions such as loneliness.

Fronto-temporal brain activity and connectivity track implicit attention to positive and negative social words in a novel socio-emotional Stroop task

Previous inconsistencies on the effects of implicitly processing positively - vs. negatively - connotated emotional words might reflect the influence of uncontrolled psycholinguistic dimensions, and/or social facets inherent in putative "emotional" stimuli. Based on the relevance of social features in semantic cognition, we developed a socio-emotional Stroop task to assess the influence of social vs. individual (non-social) emotional content, besides negative vs. positive valence, on implicit word processing. The effect of these variables was evaluated in terms of performance and RTs, alongside associated brain activity/connectivity. We matched conditions for several psycholinguistic variables, and assessed a modulation of brain activity/connectivity by trial-wise RT, to characterize the maximum of condition- and subject-specific variability. RTs were tracked by insular and anterior cingulate activations likely reflecting implicit attention to stimuli, interfering with task-performance based on condition-specific processing of their subjective salience. Slower performance for negative than neutral/positive words was tracked by left-hemispheric structures processing negative stimuli and emotions, such as fronto-insular cortex, while the lack of specific activations for positively-connotated words supported their marginal facilitatory effect. The speeding/slowing effects of processing positive/negative individual emotional stimuli were enhanced by social words, reflecting in specific activations of the right anterior temporal and orbitofrontal cortex, respectively. RTs to social positive and negative words modulated connectivity from these regions to fronto-striatal and sensorimotor structures, respectively, likely promoting approach vs. avoidance dispositions shaping their facilitatory vs. inhibitory effect. These results might help assessing the neural correlates of impaired social cognition and emotional regulation, and the effects of rehabilitative interventions.

Self-Disgust Is Associated With Loneliness, Mental Health Difficulties, and Eye-Gaze Avoidance in War Veterans With PTSD

In the present study, we examined, for the first time, the association between self-disgust, loneliness, and mental health difficulties in war veterans diagnosed with PTSD. For this purpose, we used a mixed methods design, incorporating surveys and a novel eye-tracking paradigm, and compared the findings from the PTSD veteran group (n = 19) to those from a general population group (n = 22). Our results showed that the PTSD veteran group reported almost three times higher scores in self-disgust, and significantly higher scores in loneliness and mental health difficulties (anxiety and depression), compared to the general population. Furthermore, self-disgust mediated the association between loneliness and anxiety symptoms in both groups. The results from the eye-tracking paradigm further showed that veterans with PTSD displayed a self-avoidance gaze pattern, by looking significantly more toward pictures of faces of unknown others and away from their own face—a pattern that was not replicated in the general population group. Higher self-disgust scores were significantly associated with longer total gaze to the pictures of others (vs. the self). Our findings have implications for the role of self-disgust in the mental health of war veterans.

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.

Prevalence and factors associated with anxiety and depression in older adults: Gender differences in psychosocial indicators

BACKGROUND

With increasing numbers of people living into old age, health functioning and good quality of life are central to public health policy in aging. However, quality of life for many elders is undermined by anxiety and depression. Understanding gender differences in the determinants of anxiety and depression symptoms is crucial to policy and practice.

OBJECTIVE

To examine gender-specific symptom subtypes of later-life anxiety and depression, in relation to their socio-demographic, social and health context.

METHOD

Cross-sectional study using data from The Irish Longitudinal Study on Ageing (TILDA, 2009-2011). Latent class analysis defined gender-specific symptom profiles for anxiety and depression. Correlates of latent classes were analysed using logistic regression, assessing associations between socio-demographic factors; social indicators and health indicators.

RESULTS

Four classes of self-reported anxiety and depression were derived: 'low', 'comorbidity', 'anxiety and subthreshold depression' and 'anxiety' only. With males 8% were comorbid, 26% subthreshold and 26% with anxiety only. With female 12% were comorbid, 27% subthreshold and 29% with anxiety only. While symptom expression may relate to stress from common ageing, our findings show clear gradations of symptoms associated with a range of social and health indicators.

CONCLUSION

Our findings support the actuality of comorbid depression and anxiety with further evidence for anxiety and subthreshold depression. A sizeable subgroup confirms that many older people experience anxiety only. Our study indicates the need for a more sensitive recognition of needs and a more nuanced policy agenda for older people towards improving the quality of their social life.

Oxytocin changes behavior and spatio-temporal brain dynamics underlying inter-group conflict in humans

Inter-group conflicts drive human discrimination, mass migration, and violence, but their psychobiological mechanisms remain largely unknown. Here, we investigated whether the neuropeptide oxytocin modulates behavior and spatio-temporal brain dynamics in naturalistic inter-group conflict. Eighty-six male members of natural rival social groups received either oxytocin or placebo intranasally. In a decision-making paradigm involving real monetary stakes, participants could sacrifice their own resources to modulate the monetary gains and losses of in- and out-group members. Oxytocin eliminated the reduction in out-group gains - particularly in individuals with low emotional empathy, whereas those given placebo exhibited this negative social behavior. Our spatio-temporal analysis of event-related potentials elicited by outcome valuation revealed that oxytocin replaced a neurophysiological process associated with the negative valuation of out-group gains via a process associated with positive valuation between 200-500ms after outcome presentation. Oxytocin thus seems to modulate inter-group behavior in humans via a specific alteration of valuation-related brain dynamics.

Loneliness Modulates Automatic Attention to Warm and Competent Faces: Preliminary Evidence From an Eye-Tracking Study

Social connections are essential for human survival. Loneliness is a motivational factor for building and maintaining social connections. Automatic attention occurs with little cognitive effort and plays a key role in detecting biologically salient events, such as human faces. Although previous studies have investigated the effect of loneliness on social behavior, the effect of loneliness on automatic attention to human faces remains largely unknown. The present study investigated the effects of loneliness on automatic visual attention to warmth and competence facial information, which determines facial attraction. This study included 43 participants who rated warmth and competence facial information. Then, they engaged with the target-distractor paradigm in which they saw two house images at the top and bottom and indicated whether the images were identical. During the task, we presented two faces as distractors and measured visual attention toward the faces as automatic attention because participants did not have to attend to the faces. The results showed an interactive effect between subjective loneliness and facial information on automatic attention. Warm targets automatically captured the attention of people feeling relatively lonely, whereas competent targets automatically captured the attention of those who felt less lonely. These results suggest that loneliness adaptively influences automatic processing of social information.

Loneliness and meaning in life are reflected in the intrinsic network architecture of the brain

Social relationships imbue life with meaning, whereas loneliness diminishes one's sense of meaning in life. Yet the extent of interdependence between these psychological constructs remains poorly understood. We took a multivariate network approach to examine resting-state fMRI functional connectivity’s association with loneliness and meaning in a large cohort of adults (N = 942). Loneliness and meaning in life were negatively correlated with one another. In their relationship with individually parcelled whole-brain measures of functional connectivity, a significant and reliable pattern was observed. Greater loneliness was associated with dense, and less modular, connections between default, frontoparietal, attention and perceptual networks. A greater sense of life meaning was associated with increased, and more modular, connectivity between default and limbic networks. Low loneliness was associated with more modular brain connectivity, and lower life meaning was associated with higher between-network connectivity. These findings advance our understanding of loneliness and life meaning as distinct, yet interdependent, features of sociality. The results highlight a potential role of the default network as a central hub, providing a putative neural mechanism for shifting between feelings of isolation and purpose.

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.

Negative Affect Shared with Siblings is Associated with Structural Brain Network Efficiency and Loneliness in Adolescents

Loneliness has a strong neurobiological basis reflected by its specific relationships with structural brain connectivity. Critically, affect traits are highly related to loneliness, which shows close association with the onset and severity of major depressive disorder. This diffusion imaging study was conducted on a sample of adolescent siblings to examine whether positive and negative affect traits were related to loneliness, with brain network efficiency playing a mediating role. The findings of this study confirmed that both global and average local efficiency negatively mediated the association between low positive affect and high negative affect and loneliness, and the mediation was more sensitive to sibling-shared affect traits. The findings have important implications for interventions targeted at reducing the detrimental impact of familiar negative emotional experiences and loneliness.