Loneliness across phylogeny and a call for comparative studies and animal models

Social Isolation, Loneliness, and Cardiovascular Mortality: The Role of Health Care System Interventions

PURPOSE OF REVIEW

The world is proliferating rapidly, with science and technology advancing at an incredible rate. These advances have, however, ushered in an age with a rise in social isolation (SI) and loneliness. SI is an objective term that refers to lacking social contact or support. On the other hand, loneliness is subjective and refers to feeling alone or isolated. These concepts are rapidly gaining prominence mainly due to their negative impact on the physical and psychological health of the population, mainly through behavioural modifications that encompass substance abuse, decreased physical activity and unhealthy food habits, and poor sleep hygiene. This review summarizes the pathophysiology, evaluates the evidence behind impact of SI on cardiovascular mortality, and interventions to overcome SI.

RECENT FINDINGS

Through proposed mechanisms, such as activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, both SI and loneliness have strong evidence linking them to cardiovascular morbidity and mortality. A systematic review and meta-analysis of 90 prospective cohort studies including 2,205,199 individuals reported that SI was independent predictor of cardiovascular mortality with a point estimate of 1.34 (95% confidence interval:1.25-1.44). The evidence so far is compelling and necessitates urgent action with the implementation of strict policies to tackle this issue. As healthcare professionals, it becomes even more critical to remain vigilant, recognize this insidious pandemic, and take appropriate action.

Contributions of loneliness to cognitive impairment and dementia in older adults are independent of other risk factors and Alzheimer's pathology: a narrative review

Loneliness significantly contributes to cognitive impairment and dementia in older adults. Loneliness is a distressing feeling resulting from a perceived lack of social connection (i.e., a discrepancy between desired and actual social relationships), while social isolation is a related term that can be defined by number and type of social relationships. Importantly, loneliness is distinct from social isolation in that it is associated with a distressing self-perception. The primary focus of this narrative review is the impact of chronic loneliness on cognitive impairment and dementia among older adults. Loneliness has a significant association with many factors that are related to worse cognition, and therefore we include discussion on health, mental health, as well as the physiological effects of loneliness, neuropathology, and potential treatments. Loneliness has been shown to be related to development of dementia with a hazard ratio (HR) risk comparable to having a single APOE4 gene. The relationship of dementia to loneliness appears to be at least partially independent of other known dementia risk factors that are possibly associated with loneliness, such as depression, educational status, social isolation, and physical activity. Episodic memory is not consistently impacted by loneliness, which would be more typically impaired if the mild cognitive impairment (MCI) or dementia was due to Alzheimer's disease (AD) pathology. In addition, the several longitudinal studies that included neuropathology showed no evidence for a relationship between loneliness and AD neuropathology. Loneliness may decrease resilience, or produce greater cognitive change associated with the same level of AD neuropathology. Intervention strategies to decrease loneliness in older adults have been developed but need to consider key treatment targets beyond social isolation. Loneliness needs to be assessed in all studies of cognitive decline in elders, since it significantly contributes to the variance of cognitive function. It will be useful to better define the underlying mechanism of loneliness effects on cognition to determine if it is similar to other psychological factors related to excessive stress reactivity, such as neuroticism or even depression, which are also associated with cognitive decline. It is important from a health perspective to develop better strategies to decrease loneliness in older adults.

Loneliness is associated with more trust but worse trustworthiness expectations

Subjective feelings of loneliness emerge due to unsatisfactory social relationships, representing a major risk for mental and physical well-being. Despite its social nature, evidence on how loneliness affects social behaviours and expectations is lacking. Using Bayesian analyses and economic games, we show in three different studies that lonelier individuals trusted their partners to a greater extent despite less favourable trustworthiness expectations, showing a greater discrepancy between their trusting behaviours and their expectations of others' trustworthiness. Such discrepancy was reversed in extravert individuals who also reported to be less lonely. These results provide evidence on two opposing effects of loneliness as a motivator for social connections and promoter of social withdrawal, and demonstrate the moderating role of personality traits. This work contributes to a better understanding of how loneliness impacts social behaviour and social expectations, with important downstream clinical implications for varying health conditions associated with heightened feelings of loneliness.

An unbiased method to partition diverse neuronal responses into functional ensembles reveals interpretable population dynamics during innate social behavior

In neuroscience, understanding how single-neuron firing contributes to distributed neural ensembles is crucial. Traditional methods of analysis have been limited to descriptions of whole population activity, or, when analyzing individual neurons, criteria for response categorization varied significantly across experiments. Current methods lack scalability for large datasets, fail to capture temporal changes and rely on parametric assumptions. There's a need for a robust, scalable, and non-parametric functional clustering approach to capture interpretable dynamics. To address this challenge, we developed a model-based, statistical framework for unsupervised clustering of multiple time series datasets that exhibit nonlinear dynamics into an a-priori-unknown number of parameterized ensembles called Functional Encoding Units (FEUs). FEU outperforms existing techniques in accuracy and benchmark scores. Here, we apply this FEU formalism to single-unit recordings collected during social behaviors in rodents and primates and demonstrate its hypothesis-generating and testing capacities. This novel pipeline serves as an analytic bridge, translating neural ensemble codes across model systems.

Social networking older adults with mild cognitive impairment: Systematic review protocol on their use of information and communication technology

This systematic review will identify and synthesize the emerging evidence on older adults with Mild Cognitive Impairment (MCI) utilizing Information and Communication Technology (ICT) to maintain, restore, or augment social networks. The systematic review will consider the evidence on contextual and personal factors of older adults with MCI and their ICT use for social connectedness. The evidence searches will be implemented in PsycINFO, Academic Search Complete, Medline, PubMed, and manual searches. We shall review articles that were published between January 2010 and October 2023 in English and on Information and Communication Technology utility in social networking among older adults with MCI. The process of article selection will be conducted through title screening, abstract screening; and full article screening, following the Population, Intervention, Control, Outcomes (PICO) criteria. Given that all the studies included in this review are publicly accessible and have already obtained ethical approval from their respective institutions, there is no obligation for us to seek additional ethical clearance for our systematic review. We plan to share the outcomes of the systematic review through online presentations and dissemination within the research community. The findings from this review will identify the extent of empirical evidence on older adults with MCI utilizing ICTs to maintain, restore or augment their social networks. This review will provide evidence for contextual and personal factors in older adults with MCI for the social networks with ICT use. This review will propose practical implications for the effective utilization of ICT by older adults with MCI.

Trajectories of Loneliness During Adolescence Predict Subsequent Symptoms of Depression and Positive Wellbeing

There is a need to identify the outcomes of changes in loneliness during adolescence, and to consider this within a multidimensional framework of loneliness. This study considered the effects of different trajectories of change in Isolation Loneliness and in Friendship Loneliness upon both positive wellbeing and symptoms of depression. To achieve this, 1782 (43% female; 12.92 years old at the start of the study, SD = 1.60) young people took part in a longitudinal study with four data points across 2 years. Four Isolation Loneliness trajectories and five Friendship Loneliness trajectories were identified. Youth who experienced low levels of Isolation Loneliness that subsequently increased appear to be at particular risk for poor outcomes. Similarly, initially high levels of Friendship Loneliness that decreased rapidly, or which began at a low level and only increased marginally, seem to also be a risk. Loneliness is a multi-dimensional construct and its development during adolescence impacts upon young people's depressive symptomatology and positive mental wellbeing.

Sensory perception of rivals has trait-dependent effects on plasticity in Drosophila melanogaster

The social environment has myriad effects on individuals, altering reproduction, immune function, cognition, and aging. Phenotypic plasticity enables animals to respond to heterogeneous environments such as the social environment but requires that they assess those environments accurately. It has been suggested that combinations of sensory cues allow animals to respond rapidly and accurately to changeable environments, but it is unclear whether the same sensory inputs are required in all traits that respond to a particular environmental cue. Drosophila melanogaster males, in the presence of rival males, exhibit a consistent behavioral response by extending mating duration. However, exposure to a rival also results in a reduction in their lifespan, a phenomenon interpreted as a trade-off associated with sperm competition strategies. D. melanogaster perceive their rivals by using multiple sensory cues; interfering with at least two olfactory, auditory, or tactile cues eliminates the extension of mating duration. Here, we assessed whether these same cues were implicated in the lifespan reduction. Removal of combinations of auditory and olfactory cues removed the extended mating duration response to a rival, as previously found. However, we found that these manipulations did not alter the reduction in lifespan of males exposed to rivals or induce any changes in activity patterns, grooming, or male-male aggression. Therefore, our analysis suggests that lifespan reduction is not a cost associated with the behavioral responses to sperm competition. Moreover, this highlights the trait-specific nature of the mechanisms underlying plasticity in response to the same environmental conditions.

Social reinforcement guides operant behaviour and auditory learning in a songbird

Motivation to seek social interactions is inherent to all social species. For instance, even with risk of disease transmission in a recent pandemic, humans sought out frequent in-person social interactions. In other social animals, socialization can be prioritized even over water or food consumption. Zebra finches, Taeniopygia guttata, are highly gregarious songbirds widely used in behavioural and physiological research. Songbirds, like humans, are vocal learners during development, which rely on intense auditory learning. Aside from supporting song learning, auditory learning further supports individual identification, mate choice and outcome associations in songbirds. To study auditory learning in a laboratory setting, studies often employ operant paradigms with food restriction and reinforcement and require complete social isolation, which can result in stress and other unintended physiological consequences for social species. Thus, in this work, we designed an operant behavioural method leveraging the sociality of zebra finches for goal-directed behaviours. Our approach relies on visual social reinforcement, without depriving the animals of food or social contact. Using this task, we found that visual social reinforcement was a strong motivational drive for operant behaviour. Motivation was sensitive to familiarity towards the stimulus animal and higher when engaging with a familiar versus a novel individual. We further show that this tool can be used to assess auditory discrimination learning using either songs or synthetic pure tones as stimuli. As birds gained experience in the task, they developed a strategy to maximize reward acquisition in spite of receiving more punishment, i.e. liberal response bias. Our operant paradigm provides an alternative to tasks using food reinforcement and could be applied to a variety of highly social species, such as rodents and nonhuman primates.

The relationship between perfectionism and interpersonal sensitivity with self-compassion in university students: the mediation of repetitive negative thinking

Self-compassion is a construct of positive psychology related to personality and cognitive factors. Perfectionism and interpersonal sensitivity are prevalent personality traits among university students and are associated with low self-compassion. Further research is required to comprehend how these mechanisms work in creating self-compassion. Consequently, the current study investigated the direct and indirect relationship between perfectionism and interpersonal sensitivity with self-compassion via repetitive negative thinking. To this end, a sample of 450 students studying in Tehran during the 2022 academic year was selected as the study sample. The results indicated that perfectionism and interpersonal sensitivity demonstrate a negative direct relationship with self-compassion, while perfectionism and interpersonal sensitivity exhibit an indirect relationship with self-compassion via repetitive negative thinking. Based on the findings, it can be concluded that the relationship between perfectionism and interpersonal sensitivity with self-compassion is not straightforward and that repetitive negative thinking can mediate this relationship. The results can be used to improve methods for increasing self-compassion and paying attention to personality, and cognitive factors can be an important step toward more effective self-compassion interventions.

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.

Social zebrafish: Danio rerio as an emerging model in social neuroendocrinology

The fitness benefits of social life depend on the ability of animals to affiliate with others and form groups, on dominance hierarchies within groups that determine resource distribution, and on cognitive capacities for recognition, learning and information transfer. The evolution of these phenotypes is coupled with that of neuroendocrine mechanisms, but the causal link between the two remains underexplored. Growing evidence from our research group and others demonstrates that the tools available in zebrafish, Danio rerio, can markedly facilitate progress in this field. Here, we review this evidence and provide a synthesis of the state-of-the-art in this model system. We discuss the involvement of generalized motivation and cognitive components, neuroplasticity and functional connectivity across social decision-making brain areas, and how these are modulated chiefly by the oxytocin-vasopressin neuroendocrine system, but also by reward-pathway monoamine signaling and the effects of sex-hormones and stress physiology.

Gender-specific association of loneliness and health care use in community-dwelling older adults

BACKGROUND

Loneliness in older adults is common, particularly in women. In this article, gender differences in the association of loneliness and health care use are investigated in a large sample of community-dwelling older adults.

METHODS

Data of 2525 persons (ages 55-85 years)-participants of the fourth follow- up (2011-2014) of the ESTHER study- were analyzed. Loneliness and health care use were assessed by study doctors in the course of a home visit. Gender-specific regression models with Gamma-distribution were performed using loneliness as independent variable to predict outpatient health care use, adjusted for demographic variables.

RESULTS

In older women, lonely persons were shown to have significantly more visits to general practitioners and mental health care providers in a three-month period compared to less lonely persons (p = .005). The survey found that outpatient health care use was positively associated with loneliness, multimorbidity, and mental illness in older women but not in older men. Older men had significantly more contact with inpatient care in comparison to women (p = .02).

CONCLUSIONS

It is important to consider gender when analyzing inpatient and outpatient health care use in older persons. In older women loneliness is associated with increased use of outpatient services.

The genetics of neuroticism: Insights from the Maudsley rat model and human studies

We examine some of the genetic features of neuroticism (N) taking as an animal model the Maudsley Reactive (MR) and Maudsley Nonreactive (MNR) rat strains which were selectively bred, respectively, for high and low open-field defecation (OFD) starting in the late 1950s. To draw analogies with human genetic studies, we explore the genetic correlation of N with irritable bowel syndrome (IBS). We review progress with the rat model and developments in the field of human complex trait genetics, including genetic association studies that relate to current understanding of the genetics of N. The widespread differences in the tone of the peripheral sympathetic nervous system that have been found between the Maudsley strains, particularly those observed in the colon, may underly the differences in OFD (MNR, higher sympathetic tone and zero defecation). In humans, a large genome-wide association study (GWAS) reported six genes contributing to IBS, four of which were implicated in mood and anxiety disorders or were expressed in the brain, with three of the four also expressed in the nerve fibers and ganglia of the gut. Heritability of N is estimated at around 50% in twin and family studies, and GWASs identified hundreds of loci, enabling estimation of genome-wide correlations (rg) with other traits. Significantly, the estimate for rg between risk of IBS, anxiety, N, and depression was >0.5 and suggested genetic pleiotropy without evidence for causal mechanisms. Findings on the adrenergic pharmacology of the colon, coupled with new understanding of the role of the locus ceruleus in modifying afferent information from this organ, generate hypotheses that challenge traditional cause/effect notions about the relationship of the central nervous system to peripheral events in response to stress, suggest specific targets for gene action in the Maudsley model and emphasize the value of reciprocal evaluation of genetic architecture underlying N in rodents and humans.

A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality

The associations between social isolation, loneliness and the risk of mortality from all causes, cardiovascular disease (CVD) and cancer are controversial. We systematically reviewed prospective studies on the association between social isolation, loneliness and mortality outcomes in adults aged 18 years or older, as well as studies on these relationships in individuals with CVD or cancer, and conducted a meta-analysis. The study protocol was registered with PROSPERO (reg. no. CRD42022299959). A total of 90 prospective cohort studies including 2,205,199 individuals were included. Here we show that, in the general population, both social isolation and loneliness were significantly associated with an increased risk of all-cause mortality (pooled effect size for social isolation, 1.32; 95% confidence interval (CI), 1.26 to 1.39; P < 0.001; pooled effect size for loneliness, 1.14; 95% CI, 1.08 to 1.20; P < 0.001) and cancer mortality (pooled effect size for social isolation, 1.24; 95% CI, 1.19 to 1.28; P < 0.001; pooled effect size for loneliness, 1.09; 95% CI, 1.01 to 1.17; P = 0.030). Social isolation also increased the risk of CVD mortality (1.34; 95% CI, 1.25 to 1.44; P < 0.001). There was an increased risk of all-cause mortality in socially isolated individuals with CVD (1.28; 95% CI, 1.10 to 1.48; P = 0.001) or breast cancer (1.51; 95% CI, 1.34 to 1.70; P < 0.001), and individuals with breast cancer had a higher cancer-specific mortality owing to social isolation (1.33; 95% CI, 1.02 to 1.75; P = 0.038). Greater focus on social isolation and loneliness may help improve people's well-being and mortality risk.

Amygdala AVPR1A mediates susceptibility to chronic social isolation in females

Females are more sensitive to social exclusion, which could contribute to their heightened susceptibility to anxiety disorders. Chronic social isolation stress (CSIS) for at least 7 weeks after puberty induces anxiety-related behavioral adaptations in female mice. Here, we show that Arginine vasopressin receptor 1a ( Avpr1a )-expressing neurons in the central nucleus of the amygdala (CeA) mediate these sex-specific effects, in part, via projections to the caudate putamen. Loss of function studies demonstrate that AVPR1A signaling in the CeA is required for effects of CSIS on anxiety-related behaviors in females but has no effect in males or group housed females. This sex-specificity is mediated by AVP produced by a subpopulation of neurons in the posterodorsal medial nucleus of the amygdala that project to the CeA. Estrogen receptor alpha signaling in these neurons also contributes to preferential sensitivity of females to CSIS. These data support new therapeutic applications for AVPR1A antagonists in women.

THE FEELING OF LONELINESS IN SOMATIC DISEASES AND MENTAL DISORDERS AS A NEW CHALLENGE OF MODERN MEDICINE

The aim of the paper to reflect on the meaning of the sense of loneliness caused by illness. The work is a selective narrative review with particular emphasis on attempts to define the feeling of loneliness, as well as the results of own research. The problem of loneliness affects not only patients, but also their families and caregivers. As it follows from the literature review, the issue of loneliness has been much better studied in mental disorders than in somatic diseases. In addition, the analysed research shows that the presence of the disease is the main variable determining the feeling of loneliness in the population of people in late adulthood. The feeling of loneliness turns out to be a key element of the psychosocial aspect of any disease. Therefore, it would be necessary to consider in the future how this adverse psychosocial phenomenon could be prevented.

Exploring the impact of the COVID-19 pandemic on social isolation and mental health in people with MS

BACKGROUND

People with multiple sclerosis (MS) may be disproportionally impacted by the coronavirus disease of 2019 (COVID-19) as various factors important to their functioning and quality of life are at-risk and/or compromised during the pandemic. In particular, the social distancing and quarantine practice during the pandemic maybe detrimental to MS patients' social and emotional health. Compared with the general population, MS patients may be under increased social strain and suffer worse health consequences from social isolation. To date, there has been no research examining the social consequences of the pandemic on MS patients' emotional and social health.

METHODS

This is a retrospective longitudinal study of 266 adults with MS who were followed at a large academic medical center in the Midwest. Each participant completed monthly surveys including depression, anxiety, and social health variables.

RESULTS

T-Tests shows worse anxiety (95% CI [-5.03, -3.05]; p-value < 0.001), worse depression (95% CI [-2.67, -1.03]; p-value < 0.001), and worse satisfaction with social roles (95% CI [2.37, 3.95]; p-value < 0.001) since the COVID-19 outbreak (March 2020). Social isolation is associated with worse anxiety (95% CI [-8.98, -4.58]; p-value < 0.001) and depression (95% CI [-6.88, -3.24]; p-value < 0.001). However, individuals who had in-person visits before and after the outbreak did not experience any changes in anxiety, depression, or social health.

CONCLUSION

MS patients' anxiety, depression, and social participation worsened during the COVID-19 pandemic. Social isolation is found to be associated with worse anxiety and depression. However, those who attended in-person visits for their MS treatment did not experience negative changes in their emotional or social health. This study highlights the importance of healthcare provider's alertness to MS patients' social health and the interplay between social and emotional health during the COVID-19 pandemic.

The association between autistic traits and excessive smartphone use in Chinese college students: The chain mediating roles of social interaction anxiety and loneliness

This study draws upon a large sample of Chinese college students to examine the chain mediating roles of social interaction anxiety and loneliness in the relation between autistic traits and excessive smartphone use. To test our hypothesis that social interaction anxiety and loneliness mediate the relation between autistic traits and excessive smartphone use, we recruited a sample of 1103 college students and asked them to complete an assessment that measured the degrees of autistic traits, social interaction anxiety, loneliness, and excessive smartphone use. The results showed significant correlations among these variables. More autistic traits, which are correlated with higher levels of social interaction anxiety and higher levels of loneliness, were found to be associated with excessive smartphone use. In conclusion, this study highlights the need for screening for excessive smartphone use among college students who demonstrate autistic traits. Social interaction anxiety and loneliness show great potential in screening for excessive smartphone use among college students with high levels of autistic traits. We discuss the practical implications of the findings and directions for future study.

Social connection and gene regulation during the COVID-19 pandemic: Divergent patterns for online and in-person interaction

BACKGROUND

Social connection has been linked to reduced disease risk and enhanced antiviral immunity, but it is unclear whether online social connections have similar effects to those previously documented for in-person/offline social relationships, or whether online connections can substitute for in-person social relations when the latter are restricted. We examined this question in the context of the COVID-19 pandemic, focusing specifically on an immune system gene regulation profile known as the conserved transcriptional response to adversity (CTRA), which is characterized by up-regulation of proinflammatory genes and down-regulation of genes linked to innate antiviral responses and antibody production.

METHODS

We analyzed CTRA RNA profiles in blood samples from 142 healthy young adults (69% female, 87% white) during the "social distancing" period of the COVID-19 pandemic. Mixed effect linear models quantified the relation of CTRA gene expression to measures of in-person social connection (number of friends, social eudaimonia, loneliness) and online psychosocial connection (online loneliness, perceived social value in online leisure and educational contexts, and internet use) while controlling for demographic and health factors.

RESULTS

Multiple indicators of in-person and generalized social connection were associated with lower CTRA gene expression, whereas no measure of online social connection showed any significant association with CTRA gene expression.

CONCLUSION

Experiences of in-person social connection are associated with reduced CTRA gene expression during a period of restricted social interaction. In contrast, online social relationships show no such association. Digitally mediated social relations do not appear to substantially offset the absence of in-person/offline social connection in the context of immune cell gene regulation.

Social isolation and the role of AgeTech in a post-COVID world

The COVID-19 pandemic particularly affected social connection through enforced social isolation and loss of regular activities. For healthcare systems, various initiatives have sprung up, leveraging existing technologies to connect people with services, activities, and loved ones. Here we review some AgeTech offerings to address social isolation for healthcare leadership and management to consider.

Interactions between the κ opioid system, corticotropin-releasing hormone and oxytocin in partner loss

Selective adult social attachments, or ‘pair bonds’, represent central relationships for individuals in a number of social species, including humans. Loss of a pair mate has emotional consequences that may or may not diminish over time, and that often translate into impaired psychological and physical health. In this paper, we review the literature on the neuroendocrine mechanisms for the emotional consequences of partner loss, with a special focus on hypothesized interactions between oxytocin, corticotropin-releasing hormone and the κ opioid system.

This article is part of the theme issue ‘Interplays between oxytocin and other neuromodulators in shaping complex social behaviours’.

Interpersonal predictors of loneliness in Japanese children: variable- and person-centered approaches

BACKGROUND

Loneliness in children has been a major topic of interest in both clinical and developmental psychology. Further studies to investigate predictors of loneliness are needed for educational practices.

METHODS

A total of 1088 late elementary school-aged children (48.81% boys, M_age = 10.35) participated in a 1-year longitudinal survey. We used hierarchical linear modeling and mover-stayer latent transition analysis.

DISCUSSION

Findings from the variable- and person- centered approaches suggested that less positive peer relations, higher victimization, and higher relational aggression are predictors of higher future loneliness. Meanwhile, both approaches did not reach an agreement concerning predictors to reduce loneliness. This result highlighted a utility of a combined approach and sounded an alarm for overreliance on the variable-centered approach dominating child research.

CONCLUSION

To protect young children from loneliness, it will be more beneficial to prevent the development of loneliness rather than to apply interventions to reduce loneliness once established. Preventive practices need to be implemented to protect children from loneliness.

Exploring the effect of loneliness on fear: Implications for the effect of COVID-19-induced social disconnection on anxiety

The consequences of the COVID-19 pandemic have resulted in many disruptions to daily life, including an abrupt increase in social disconnection. As measures were put in place to combat the spread of COVID-19, people across the globe began living in states of limited social contact, fostering feelings of social isolation and loneliness. Previous literature suggests that these increases in social disconnection can have profound effects on both physical and mental health, perhaps especially in the case of fear disorders. The combination of feeling disconnected from others and the high level of daily threat experienced due to COVID-19 created conditions under which dysfunctional and persistent fears were especially likely to develop. Building on current understanding of the harmful effects of social disconnection on well-being in general as well as specific implications for fear, here we present findings from three preliminary investigations that are the first to directly examine the effects of loneliness on how fears are learned and maintained. The Results of this work show that loneliness impairs the process by which fears are extinguished, which is central to both the regulation of fear and treatment of fear disorders, and provide insight into potential avenues to mitigate such effects.

Online Emotional Support Accompany Group Intervention and Emotional Change of the Public During the COVID-19 Pandemic: A Multi-Period Data Analysis From China

COVID-19 has made it difficult to adopt traditional face-to-face psychological intervention under this situation because of the blocked down and social distancing, which brings big psychological crisis to the public among the global. To explore the emotional change of the public in China at the outburst of the pandemic at different phases, to establish an online working platform and create a new model of an online intervention to hold public emotions under pandemic, and test its effectiveness, so to give advisement for government emergency management system. We established an online organization to work for this program ad innovated a model of online group counseling with online emotional support accompany group (OESAG) right after the outburst of a pandemic. We analyzed 53 OESAGs from February 10 to April 9, including 555 application forms, 253 feedback from members, and 139 feedback from group leaders by using NVivo and SPSS to explore the evolution and characteristics of public emotion during COVID-19 and the effectiveness of OESAG. Our results showed that the emotional changes of members ranged from shock to depression to positive. The public's emotions swiftly changed from stress, anxiety, and isolation, to the hope of returning to work or finding a job during the pandemic with the help of OESAG. OESAG has effectively regulated the negative emotions of members by conducting psychological crisis intervention to provide members a space to communicate with each other, especially the female and frontline staff. Policy makers can set up an online systematic psychological crisis intervention system as soon as possible to make up for the lack of psychological assistance in the emergency management system.

Social isolation and oxytocin antagonism increase emotion-related behaviors and heart rate in female prairie voles

Social isolation influences depression- and anxiety-related disorders and cardiac function. Oxytocin may mediate these conditions through interactions with social behavior, emotion, and cardiovascular function, via central and/or peripheral mechanisms. The present study investigated the influence of oxytocin antagonism using L-368,899, a selective oxytocin receptor antagonist that crosses the blood-brain barrier, on depression- and anxiety-related behaviors and heart rate in prairie voles. This rodent species has translational value for investigating interactions of social stress, behavior, cardiac responses, and oxytocin function. Adult female prairie voles were socially isolated or co-housed with a sibling for 4 weeks. A subset of animals in each housing condition was subjected to 4 sessions of acute L-368,899 (20 mg/kg, ip) or saline administration followed by a depression- or anxiety-related behavioral assessment. A subset of co-housed animals was evaluated for cardiac function following acute administration of L-368,899 (20 mg/kg, ip) and during behavioral assessments. Social isolation (vs. co-housing) increased depression- and anxiety-related behaviors. In isolated animals, L-368,899 (vs. vehicle) did not influence anxiety-related behaviors but exacerbated depression-related behaviors. In co-housed animals, L-368,899 exacerbated depression-related behaviors and increased heart rate at baseline and during behavioral tests. Social isolation produces emotion-related behaviors in prairie voles; central and/or peripheral oxytocin antagonism exacerbates these behavioral signs. Oxytocin antagonism induces depression-relevant behaviors and increases basal and stressor-reactive heart rate in co-housed prairie voles, similar to the consequences of social isolation demonstrated in this model. These results provide translational value for humans who experience behavioral and cardiac consequences of loneliness or social stress.

The immunomodulatory effects of social isolation in mice are linked to temperature control

Living in isolation is considered an emerging societal problem that negatively affects the physical wellbeing of its sufferers in ways that we are just starting to appreciate. This study investigates the immunomodulatory effects of social isolation in mice, utilising a two-week program of sole cage occupancy followed by the testing of immune-inflammatory resilience to bacterial sepsis. Our results revealed that mice housed in social isolation showed an increased ability to clear bacterial infection compared to control socially housed animals. These effects were associated with specific changes in whole blood gene expression profile and an increased production of classical pro-inflammatory cytokines. Interestingly, equipping socially isolated mice with artificial nests as a substitute for their natural huddling behaviour reversed the increased resistance to bacterial sepsis. Together these results suggest that the control of body temperature through social housing and huddling behaviour are important factors in the regulation of the host immune response to infection in mice and might provide another example of the many ways by which living conditions influence immunity.

You Are Not Alone!

Abstract. Experiencing ostracism is a painful situation that can urge a desire to restore social bonds. However, few studies have investigated the conditions under which it leads to ingroup identification. In three studies using minimal groups ( N = 611), we have investigated the consequences of coexperiencing ostracism for group identification and well-being. In Study 1a and 1b ( N = 171; N = 211), the results showed that sharing a common experience of ostracism with an ingroup member increases ingroup identification but does not improve psychological needs during the ostracism experience. In Study 2 ( N = 230), we replicated our results on identification and showed that sharing ostracism fosters psychological closeness with the partner ostracized but does not moderate need recovery.

Are They Still Friends? Friendship Stability of Adolescents With Chronic Pain: 1-Year Follow-Up

Most adolescents identify their best friend as their main source of social support. Adolescents with chronic pain (ACP) report the loss of friendships due to pain. Friendships protect against loneliness and depression, yet adolescents with pain experience increased levels of loneliness and depression compared to peers. This longitudinal study examines the friendship stability of dyads that included an adolescent with chronic pain compared to non-pain friendship dyads as well as the factors contributing to a friendship breakup. Eighty-three participants from 61 same-sex friendship dyads across 3 sites participated in a 1-year follow-up survey designed to capture friendship features, indices of social-emotional well-being, pain characteristics, and friendship stability. Chi-square, repeated measures ANOVA, and logistic regression were used to analyze the data. Dyads that included an ACP experienced higher rates of friendship breakup. The shorter length of friendship and having chronic pain predicted a friendship breakup at time 2. ACP continues to experience worse scores on indices of social-emotional well-being that are not predicted with a friendship breakup. Understanding what contributes to positive long-term friendships for those with pain may inform strategies to maintain and improve friendships for those with pain and who experience social challenges.

Oxytocin and love: Myths, metaphors and mysteries

Oxytocin is a peptide molecule with a multitude of physiological and behavioral functions. Based on its association with reproduction - including social bonding, sexual behavior, birth and maternal behavior - oxytocin also has been called “the love hormone.” This essay specifically examines association and parallels between oxytocin and love. However, many myths and gaps in knowledge remain concerning both. A few of these are described here and we hypothesize that the potential benefits of both love and oxytocin may be better understood in light of interactions with more ancient systems, including specifically vasopressin and the immune system. Oxytocin is anti-inflammatory and is associated with recently evolved, social solutions to a variety of challenges necessary for mammalian survival and reproduction. The shared functions of oxytocin and love have profound implications for health and longevity, including the prevention and treatment of excess inflammation and related disorders, especially those occurring in early life and during periods of chronic threat or disease.

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Oxytocin is a peptide molecule with functions that support a sense of safety, sociality, as well as survival and reproduction.

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Oxytocin is associated with social and neuroimmune solutions to chronic stress.

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The related, but more primitive, peptide vasopressin supports more individualistic survival strategies.

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Controversies and myths surround the properties of oxytocin and love.

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.

Parental Punishment and Adolescents' Loneliness: A Moderated Mediation Model of General Self-Concept and Teacher-Student Relationships

Background: Loneliness adversely affects physical and mental health; therefore, it is necessary to explore its related influencing factors and mechanisms. This study investigated the mediating role of general self-concept in the association between parental punishment (PP) and adolescent loneliness and as well as the moderating role of teacher–student relationships (TSR) in Chinese students.

Methods: Data were obtained from 1,169 Chinese students (10–18years old) using several self-report questionnaires: the Egna Minnen av Barndoms Uppfostran (EMBU), Self-Description Questionnaire (SDQ), Teacher–Student Relationships Scale (TSR), and UCLA Loneliness Scale. Data were analyzed with IBM SPSS 22.0, and the PROCESS macro program.

Results: (1) Parental punishment had a positive predictive effect on adolescent loneliness, (2) parental punishment predicted adolescent loneliness not only directly but also indirectly through the mediating effect of general self-concept, and (3) teacher–student relationships moderated the influence of PP on adolescent loneliness.

Conclusion: Adolescent loneliness is less affected by parental punishment when TSRs are better. Additionally, when adolescents are punished less by their parents and have good teacher–student relationships, they have higher general self-concepts.

Limitations: This study’s cross-sectional research design was unable to show causal relationships among the factors influencing adolescent loneliness.

Solitary Living Brings a Decreased Weight and an Increased Agility to the Domestic Silkworm, Bombyx mori

Simple Summary

We identified and validated that solitary living brings a decreased weight and an increased agility to silkworms. Solitary silkworms have a faster movement in response to food or physical stress than group-living counterparts. These contradict previous thoughts that solitary or lonely life is always harmful to animals or humans. We identified differently expressed genes (DEGs) and microRNAs (DEmiRNAs) resulted from solitary living. These DEGs and DEmiRNAs are functionally associated with the phenotypic changes led by solitary living.

Abstract

The domestic silkworms, Bombyx mori, always live in groups and little is known of the outcomes of solitary living. We bred solitary silkworms and performed a comprehensive investigation of the difference between solitary and group-living silkworms. The results show that solitary silkworms had significantly lower weights than group-living counterparts. Moreover, solitary silkworms had faster movements under food luring or heat stress than the group-living ones, supported by extensive behavior experiments. These findings inferred that an increased agility resulted from solitary living. For an understanding of the molecular mechanism associated with solitary living, we performed integrated mRNA and miRNA (microRNA) sequencing of tissues for solitary and group-living silkworms. We identified 165 differently expressed genes (DEGs) and 6 differently expressed miRNAs between the solitary and group-living silkworms. Functional and pathway analyses indicated that these DEGs are associated with weight loss and agility increase. These findings compose a sketch depicting an association between the phenotypes and genes resulted from solitary living and refresh the understanding of solitary living and loneliness, which has an increased prevalence in our modern society.

Chronic social isolation signals starvation and reduces sleep in Drosophila

Social isolation and loneliness have potent effects on public health1-4. Research in social psychology suggests that compromised sleep quality is a key factor that links persistent loneliness to adverse health conditions5,6. Although experimental manipulations have been widely applied to studying the control of sleep and wakefulness in animal models, how normal sleep is perturbed by social isolation is unknown. Here we report that chronic, but not acute, social isolation reduces sleep in Drosophila. We use quantitative behavioural analysis and transcriptome profiling to differentiate between brain states associated with acute and chronic social isolation. Although the flies had uninterrupted access to food, chronic social isolation altered the expression of metabolic genes and induced a brain state that signals starvation. Chronically isolated animals exhibit sleep loss accompanied by overconsumption of food, which resonates with anecdotal findings of loneliness-associated hyperphagia in humans. Chronic social isolation reduces sleep and promotes feeding through neural activities in the peptidergic fan-shaped body columnar neurons of the fly. Artificial activation of these neurons causes misperception of acute social isolation as chronic social isolation and thereby results in sleep loss and increased feeding. These results present a mechanistic link between chronic social isolation, metabolism, and sleep, addressing a long-standing call for animal models focused on loneliness7.

Effect of Group Cognitive Behavioural Therapy on Loneliness in a Community Sample of Older Adults: A Secondary Analysis of a Randomized Controlled Trial

OBJECTIVES

Research suggests a link between loneliness, depression, and anxiety. Multiple studies have examined treatment programs for loneliness; however, none have examined the efficacy of Cognitive Behavioral Therapy (CBT) for depression and anxiety in reducing loneliness.

METHODS

Change in loneliness in sixty-two older adults (≥60 yrs; 65% female) who took part in a previously reported randomized controlled trial for the treatment of comorbid depression and anxiety was examined. Older adults were randomized to a 12-week group CBT or waitlist control condition. Participants who took part in CBT were followed-up three months later.

RESULTS

Linear Mixed Model analyses indicated that after controlling for baseline cognition, depression, and anxiety, participants who completed CBT experienced a significant decrease in loneliness while the control group did not. This reduction was maintained at follow-up.

CONCLUSIONS

CBT programs for depression and anxiety are likely to be effective at reducing loneliness. This may be due to shared underlying cognitive and behavioral mechanisms between loneliness, depression, and anxiety such as sensitivity to perceived threat and social withdrawal. Further research is needed to understand if specific loneliness interventions are more effective.

CLINICAL IMPLICATIONS

CBT may be effective at reducing loneliness among older adults with depression and anxiety.

Loneliness of the Blind and the Visually Impaired

Loneliness has been termed a social epidemic, especially when experienced by people with disabilities. In order to better understand how loneliness is experienced in vulnerable populations, the present study compared the qualitative dimensions of loneliness of the blind and visually impaired with the general population not on the frequency or intensity of their loneliness, but on its qualitative aspects. One hundred and eighty-seven participants responded to a questionnaire which measured the qualitative aspects of loneliness on five subscales: Emotional distress, social inadequacy, Growth and discovery, social isolation, and emotional alienation. Results indicated that as expected, the two populations differed significantly in their scores on four of the five subscales (except emotional alienation), but in the opposite direction of what was expected. That may indicate that the visually impaired person's ability to transcend their blindness, and connect with those around them, and the larger society, in different-and not necessarily less meaningful-manner than the seeing general population. As expected, the visually impaired scored significantly higher than the general population on the Growth and development subscale.

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.

The social network: Neural control of sex differences in reproductive behaviors, motivation, and response to social isolation

Social animal species present a vast repertoire of social interactions when encountering conspecifics. Reproduction-related behaviors, such as mating, parental care, and aggression, are some of the most rewarding types of social interactions and are also the most sexually dimorphic ones. This review focuses on rodent species and summarizes recent advances in neuroscience research that link sexually dimorphic reproductive behaviors to sexual dimorphism in their underlying neuronal circuits. Specifically, we present a few possible mechanisms governing sexually-dimorphic behaviors, by hypothalamic and reward-related brain regions. Sex differences in the neural response to social isolation in adulthood are also discussed, as well as future directions for comparative studies with naturally solitary species.

Koi (Cyprinus rubrofuscus) Seek Out Tactile Interaction with Humans: General Patterns and Individual Differences

The study of human-animal interactions has provided insights into the welfare of many species. To date, however, research has largely focused on human relationships with captive mammals, with relatively little exploration of interactions between humans and other vertebrates, despite non-mammals constituting the vast majority of animals currently living under human management. With this study, we aimed to address this gap in knowledge by investigating human-fish interactions at a community garden/aquaponics learning-center that is home to approximately 150 goldfish (Carassius auratus) and seven adult and two juvenile koi (Cyprinus rubrofuscus). After a habituation period (July-September 2019) during which time the fish were regularly provided with the opportunity to engage with the researcher's submerged hand, but were not forced to interact with the researcher, we collected video data on 10 non-consecutive study days during the month of October. This procedure produced 18~20-min interaction sessions, 10 during T1 (when the experimenter first arrived and the fish had not been fed) and eight during T2 (20-30 min after the fish had been fed to satiation; two sessions of which were lost due equipment malfunction). Interactions between the researcher and the seven adult koi were coded from video based on location (within reach, on the periphery, or out of reach from the researcher) and instances of physical, tactile interaction. Analyses revealed that overall, koi spent more time than expected within reach of the researcher during both T1 (p < 0.02) and T2 (p < 0.03). There were also substantial differences between individuals' overall propensity for being within-reach and engaging in physical interaction. These results show that koi will voluntarily interact with humans and that individual koi display unique and consistent patterns of interaction. By providing quantitative data to support anecdotal claims that such relationships exist around the world, this research contributes to the ongoing discoveries highlighting the profound dissonance between how humans think about and treat fish and who fish actually are, thereby emphasizing the necessity of stronger moral and legal protections for fishes.

An observational study protocol to explore loneliness and systemic inflammation in an older adult population with chronic venous leg ulcers

BACKGROUND

Chronic venous leg ulcers (CVLUs) are the most common type of lower extremity wound. Even when treated with evidenced-based care, 30-50% of CVLUs fail to heal. A specific gap exists about the association between psychosocial stressors, particularly loneliness, and biomarkers of inflammation and immunity. Loneliness is highly prevalent in persons with CVLUs, has damaging effects on health, and contributes to the development of multiple chronic conditions, promotes aberrant inflammation, and diminishes healing. However, the confluence of loneliness, inflammation and the wound healing trajectory has not been elucidated; specifically whether loneliness substantially mediates systemic inflammation and alters healing over time. This study seeks to address whether there is a specific biomarker profile associated with loneliness, CVLUs, and wound healing that is different from non-lonely persons with CVLUs.

METHODS

An observational prospective study will identify, characterize and explore associations among psychosocial stressors, symptoms and biomarkers between 2 CVLU groups, with loneliness+ (n = 28) and without loneliness- (n = 28) during 4 weeks of wound treatment, measured at 3 time points. We will examine psychosocial stressors and symptoms using psychometrically-sound measures include PROMIS® and other questionnaires for loneliness, social isolation, depression, anxiety, stigma, sleep, fatigue, pain, quality of life, cognition, and function. Demographics data including health history, sex, age, wound type and size, wound age, and treatment will be recorded from the electronic health record. We will characterize a biomarker panel of inflammatory genes including chemotaxic and growth factors, vascular damage, and immune regulators that express in response to loneliness to loneliness and CVLUs using well-established RNA sequence and PCR methods for whole blood samples. In an exploratory aim we will explore whether age and sex/psychological stressors and symptoms indicate potential moderation/mediation of the effect of loneliness on the biomarker profile over the study period.

DISCUSSION

This study will provide insight into the influence of psychosocial stressors, symptoms, and biological mechanisms on wound healing, towards advancing a future healing prediction model and interventions to address these stressors and symptoms experienced by persons with CVLUs.

Genetic risk for major depressive disorder and loneliness in sex-specific associations with coronary artery disease

Major depressive disorder (MDD) and loneliness are phenotypically and genetically correlated with coronary artery disease (CAD), but whether these associations are explained by pleiotropic genetic variants or shared comorbidities is unclear. To tease apart these scenarios, we first assessed the medical morbidity pattern associated with genetic risk factors for MDD and loneliness by conducting a phenome-wide association study in 18,385 European-ancestry individuals in the Vanderbilt University Medical Center biobank, BioVU. Polygenic scores for MDD and loneliness were developed for each person using previously published meta-GWAS summary statistics, and were tested for association with 882 clinical diagnoses ascertained via billing codes in electronic health records. We discovered strong associations with heart disease diagnoses, and next embarked on targeted analyses of CAD in 3893 cases and 4197 controls. We found odds ratios of 1.11 (95% CI, 1.04-1.18; P 8.43 × 10^-4) and 1.13 (95% CI, 1.07-1.20; P 4.51 × 10^-6) per 1-SD increase in the polygenic scores for MDD and loneliness, respectively. Results were similar in patients without psychiatric symptoms, and the increased risk persisted in females even after adjusting for multiple conventional risk factors and a polygenic score for CAD. In a final sensitivity analysis, we statistically adjusted for the genetic correlation between MDD and loneliness and re-computed polygenic scores. The polygenic score unique to loneliness remained associated with CAD (OR 1.09, 95% CI 1.03-1.15; P 0.002), while the polygenic score unique to MDD did not (OR 1.00, 95% CI 0.95-1.06; P 0.97). Our replication sample was the Atherosclerosis Risk in Communities (ARIC) cohort of 7197 European-ancestry participants (1598 incident CAD cases). In ARIC, polygenic scores for MDD and loneliness were associated with hazard ratios of 1.07 (95% CI, 0.99-1.14; P = 0.07) and 1.07 (1.01-1.15; P = 0.03), respectively, and we replicated findings from the BioVU sensitivity analyses. We conclude that genetic risk factors for MDD and loneliness act pleiotropically to increase CAD risk in females.

Effects of Chronic and State Loneliness on Heart Rate Variability in Women

BACKGROUND

Loneliness, the subjective experience of social isolation, represents one of the largest risk factors for physical illness and early death in humans. However, the mechanisms by which loneliness leads to adverse health outcomes are not well understood.

PURPOSE

In this study, we examined altered parasympathetic nervous system function as a potential pathway by which chronic loneliness and state loneliness may "get under the skin" to impact cardiovascular physiology.

METHODS

In a controlled laboratory setting, vagally mediated resting heart rate variability (HRV), HRV reactivity to an induction of state loneliness, and HRV reactivity to a cognitive challenge task were assessed in a sample of 316 healthy women (18-28 years).

RESULTS

Greater chronic loneliness in women predicted lower resting HRV, an independent risk factor for cardiovascular disease and all-cause mortality, after controlling for demographic, psychosocial, and health behavior covariates. Furthermore, women higher in chronic loneliness experienced significantly larger increases in HRV to state loneliness and reported significantly higher levels of negative affect immediately following state loneliness, compared with their less chronically lonely counterparts. Chronic loneliness also predicted blunted HRV reactivity-a maladaptive physiological response-to cognitive challenge.

CONCLUSIONS

The current findings provide evidence that chronic loneliness is associated with altered parasympathetic function (both resting HRV and HRV reactivity) in women, and that the immediate experience of state loneliness is linked to a proximate increase in HRV among chronically lonely women. Results are discussed in terms of implications for cardiovascular health and the evolutionary functions of loneliness.

The role of oxidative stress in cardiovascular disease caused by social isolation and loneliness

Loneliness and social isolation are common sources of chronic stress in modern society. Epidemiological studies have demonstrated that loneliness and social isolation increase mortality risk as much as smoking or alcohol consumption and more than physical inactivity or obesity. Loneliness in human is associated with higher blood pressure whereas enhanced atherosclerosis is observed in animal models of social isolation. Loneliness and social isolation lead to activation of the hypothalamic-pituitary-adrenocortical (HPA) axis, enhanced sympathetic nerve activity, impaired parasympathetic function and a proinflammatory immune response. These mechanisms have been implicated in the development of cardiovascular disease conferred by social isolation although a causal relationship has not been established so far. There is evidence that oxidative stress is likely to be a key molecular mechanism linking chronic psychosocial stress to cardiovascular disease. NADPH oxidase-mediated oxidative stress in the hypothalamus has been shown to be required for social isolation-induced HPA axis activation in socially isolated rats. Oxidative stress in the rostral ventrolateral medulla is also a key regulator of sympathetic nerve activity. In the vasculature, oxidative stress increases vascular tone and promote atherogenesis through multiple mechanisms. Thus, preventing oxidative stress may represent a therapeutic strategy to reduce the detrimental effects of social stress on health.