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

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.

Is loneliness a feasible treatment target in psychosis?

PURPOSE

Loneliness is a challenge for individuals with psychosis; however, interventions rarely target loneliness in this group.

METHOD

We developed a pilot positive psychology group intervention designed to reduce loneliness in psychosis and examined its feasibility and acceptability.

RESULTS

Sixteen participants attended 5.38 (SD = 0.70) out of six sessions, with a dropout rate of 10%. Participants were significantly less lonely at post-treatment (p < 0.001, d = 1.51), and maintained their improvements from post-treatment to follow-up (p = 0.81, d = 0.07).

CONCLUSIONS

Loneliness may be a feasible and acceptable treatment target within psychosocial treatments.

Why Loneliness Interventions Are Unsuccessful: A Call for Precision Health

Background

Loneliness has drawn increasing attention over the past few decades due to rising recognition of its close connection with serious health issues, like dementia. Yet, researchers are failing to find solutions to alleviate the globally experienced burden of loneliness.

Purpose

This review aims to shed light on possible reasons for why interventions have been ineffective. We suggest new directions for research on loneliness as it relates to precision health, emerging technologies, digital phenotyping, and machine learning.

Results

Current loneliness interventions are unsuccessful due to (i) their inconsideration of loneliness as a heterogeneous construct and (ii) not being targeted at individuals' needs and contexts. We propose a model for how loneliness interventions can move towards finding the right solution for the right person at the right time. Taking a precision health approach, we explore how transdisciplinary research can contribute to creating a more holistic picture of loneliness and shift interventions from treatment to prevention.

Conclusions

We urge the field to rethink metrics to account for diverse intra-individual experiences and trajectories of loneliness. Big data sharing and evolving technologies that emphasize human connection raise hope for realizing our model of precision health applied to loneliness. There is an urgent need for precise, integrated, and theory-driven interventions that focus on individuals' needs and the subjective burden of loneliness in the ageing context.

A Clinician and Service User's Perspective on Managing MS: Pleasure, Purpose, Practice

There is a growing body of evidence that points to an important role for modification of lifestyle factors and promotion of health-related quality of life in the secondary prevention of disease progression in multiple sclerosis (D'Hooghe et al., 2010; Weiland et al., 2014; Hadgkiss et al., 2015). As a clinical psychologist diagnosed with multiple sclerosis in 2012 I have gained a unique insight into ways in which people living with MS and clinicians can usefully integrate evidence-based lifestyle modifications that enhance self-efficacy and self-management to improve wider psychological and physical health. The framework presented here enables clinicians to engage in salutogenic health promotion by placing value upon the importance of healthy, evidence-based behavior change. Furthermore, the framework provides a structure which can empower and provide guidance for people living with MS on what and how to implement and sustain behavior change and emotional wellbeing in the face of this life-changing diagnosis.

Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

BACKGROUND

Although a large body of research has focused on social isolation and loneliness, few studies have examined social isolation and loneliness together. The objectives of this study were to examine: 1) the relationship between four groups derived from combining social isolation and loneliness (socially isolated and lonely; only socially isolated; only lonely; neither socially isolated nor lonely) and the desire for more social participation, and social support; and 2) the relationship between the four groups and psychological distress.

METHODS

The study was based on the Comprehensive Cohort of the Canadian Longitudinal Study on Aging. Using CLSA baseline data (unweighted N = 30,079), ordinary and logistic regression analysis was used to examine the cross-sectional relationship between the four social isolation/loneliness groups and desire for more social participation and four types of social support (tangible, positive interaction, affection, and emotional support). Prospective logistic regression analysis was possible for psychological distress, which was derived from the Maintaining Contact Questionnaire administered about 18 months after the baseline questionnaire (unweighted N = 28,789).

RESULTS

Findings indicate that being socially isolated and lonely was associated with the most social support gaps; this group also had an increased likelihood of psychological distress, relative to those who were neither socially isolated nor lonely. Participants who were only socially isolated, and those only lonely also perceived some social support gaps. In addition, the only lonely group was more likely to be psychologically distressed than the only socially isolated group and the neither isolated nor lonely group.

CONCLUSION

Examining the four social isolation/loneliness was useful, as it provided more nuanced risk profiles than would have been possible had we examined social isolation and loneliness separately. Findings may suggest avenues for interventions tailored to the unique needs of at-risk individuals.

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

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

Pro-neurogenic effect of fluoxetine in the olfactory bulb is concomitant to improvements in social memory and depressive-like behavior of socially isolated mice

Although loneliness is a human experience, it can be estimated in laboratory animals deprived from physical contact with conspecifics. Rodents under social isolation (SI) tend to develop emotional distress and cognitive impairment. However, it is still to be determined whether those conditions present a common neural mechanism. Here, we conducted a series of behavioral, morphological, and neurochemical analyses in adult mice that underwent to 1 week of SI. We observed that SI mice display a depressive-like state that can be prevented by enriched environment, and the antidepressants fluoxetine (FLX) and desipramine (DES). Interestingly, chronic administration of FLX, but not DES, was able to counteract the deleterious effect of SI on social memory. We also analyzed cell proliferation, neurogenesis, and astrogenesis after the treatment with antidepressants. Our results showed that the olfactory bulb (OB) was the neurogenic niche with the highest increase in neurogenesis after the treatment with FLX. Considering that after FLX treatment social memory was rescued and depressive-like behavior decreased, we propose neurogenesis in the OB as a possible mechanism to unify the FLX ability to counteract the deleterious effect of SI.

The neuroscience of unmet social needs

John Cacioppo has compared loneliness to hunger or thirst in that it signals that one needs to act and repair what is lacking. This paper reviews Cacioppo's and others' contributions to our understanding of neural mechanisms underlying social motivation in humans and in other social species. We focus particularly on the dopaminergic reward system and try to integrate evidence from animal models and human research. In rodents, objective social isolation leads to increased social motivation, mediated by the brains' mesolimbic dopamine system. In humans, social rejection can lead to either increased or decreased social motivation, and is associated with activity in the insular cortex; while chronic loneliness is typically associated with decreased social motivation but has been associated with altered dopaminergic responses in the striatum. This mixed pattern of cross-species similarities and differences may arise from the substantially different methods used to study unmet social needs across species, and suggests the need for more direct and deliberate cross-species comparative research in this critically important domain.

Does loneliness 'get under the skin'? Associations of loneliness with subsequent change in inflammatory and metabolic markers

Objectives: To expand existing knowledge about the associations of late-life loneliness with subsequent change in inflammation as well as with metabolic dysregulation, using national representative longitudinal data. The current analysis also explores age, gender, and race differences in these pre-disease pathways. Method: The analysis is based on data from the 2005-06 and 2010-11 waves of the National Social Life, Health, and Aging Project (NSHAP)-a longitudinal survey conducted among a representative sample of community-dwelling Americans aged 57-85. Adjusted logistic regression models were used to examine associations of loneliness with changes in C-reactive protein (CRP), Glycated hemoglobin (HbA1c), Body Mass Index (BMI), Waist Circumference (WC), and metabolic burden. Results: Loneliness was found to be associated with a change for the worse in most of the metabolic bio-markers. Specifically, lonely older adults had 39%-71% higher odds of developing prospective risk levels in three out of the four metabolic bio-markers that were measured: HbA1c, BMI, and metabolic burden. Salient differences by race were found in this regard. Whereas loneliness was not significantly associated with HbA1c risk levels and BMI among the Whites, the prospective risk of high HbA1c was more than five times greater and the risk of high BMI scores was three times greater among Hispanics who experienced loneliness than among the not-lonely Hispanic group. Conclusions: The robust impact of loneliness on prospective changes for the worse in levels of various metabolic bio-markers that are closely associated with morbidity highlights the need for prevention, coping with, and reducing loneliness.

Love is a physiological motivation (like hunger, thirst, sleep or sex)

The multitude of terms associated with love has given rise to a false perception of love. In this paper, only maternal and romantic love are considered. Love is usually regarded as a feeling, motivation, addiction, passion, and, above all, an emotion. This confusion has consequences in the lives of human beings, leading not only to divorces, suicides, femicides but possibly also to a number of mental illnesses and suffering. Therefore, it is crucial to first clarify what is meant by emotion, motivation and love. This work aims to finally place love within the category of physiological motivations, such as hunger, thirst, sleep, or sex, on the basis that love is also essential for human survival, especially in childhood. Love is presented from an evolutionary perspective. Some other similarities between love and other physiological motivations are pointed out, such as its importance for appropriate human development, both its ontogeny and its permanence, and the long-lasting consequences of abuse and neglect. There are summarized reasons that account for this, such as the fact that physiological motivations are essential for survival and that love is an essential motivation for the survival of human offspring. Other reasons are that minimum changes in the quantity and quality of love alters development, that there can be a variety of neurophysiological and behavioural states within a motivation, and that motivations (also love) appear and change throughout development. Also, motivations and love sometimes may lead to an addictive behaviour. Finally, it is recognized that once physiological motivations (and love) appear, they become permanent. In a third section, some potential social, cultural, clinical and scientific consequences of the proposed consideration of love as a motivation are discussed. Accordingly, love's recognition as a motivation in the clinical field would imply a better understanding of its disorders and its inclusion in classifications manuals such as The Diagnostic and Statistical Manual of Mental Disorders (DSM), or in the International Classification of Diseases (ICD). Considering love as a motivation rather than an emotion could also impact the results of scientific research (an example is included). A comprehensive understanding of these questions could potentially allow for a new therapeutic approach in the treatment of mental illness, while offering an all-inclusive evolutionary explanation of cultural phenomena such as the origin and diffusion of both language and art. Love should be understood as a physiological motivation, like hunger, sleep or sex, and not as an emotion as it is commonly considered.

Acute social isolation alters neurogenomic state in songbird forebrain

Prolonged social isolation has negative effects on brain and behavior in humans and other social organisms, but neural mechanisms leading to these effects are not understood. Here we tested the hypothesis that even brief periods of social isolation can alter gene expression and DNA methylation in higher cognitive centers of the brain, focusing on the auditory/associative forebrain of the highly social zebra finch. Using RNA sequencing, we first identified genes that individually increase or decrease expression after isolation and observed general repression of gene sets annotated for neurotrophin pathways and axonal guidance functions. We then pursued 4 genes of large effect size: EGR1 and BDNF (decreased by isolation) and FKBP5 and UTS2B (increased). By in situ hybridization, each gene responded in different cell subsets, arguing against a single cellular mechanism. To test whether effects were specific to the social component of the isolation experience, we compared gene expression in birds isolated either alone or with a single familiar partner. Partner inclusion ameliorated the effect of solo isolation on EGR1 and BDNF, but not on FKBP5 and UTS2B nor on circulating corticosterone. By bisulfite sequencing analysis of auditory forebrain DNA, isolation caused changes in methylation of a subset of differentially expressed genes, including BDNF. Thus, social isolation has rapid consequences on gene activity in a higher integrative center of the brain, triggering epigenetic mechanisms that may influence processing of ongoing experience.

Oxytocin administration prevents cellular aging caused by social isolation

Chronic stressors, such as chronic isolation in social mammals, can elevate glucocorticoids, which can affect cellular mechanisms of aging, including increased levels of oxidative stress and shortened telomere lengths. Recent work in the selectively social prairie vole (Microtus ochrogaster) suggests that oxytocin and social support may mitigate some of the negative consequences of social isolation, possibly by reducing glucocorticoid levels. We investigated the influences of isolation, social support, and daily oxytocin injections in female prairie voles. Glucocorticoid levels, oxidative damage, telomere length, and anhedonia, a behavioral index of depression, were measured throughout the study. We found that six weeks of chronic isolation led to increased glucocorticoid levels, oxidative damage, telomere degradation and anhedonia. However, daily oxytocin injections in isolated voles prevented these negative consequences. These findings demonstrate that chronic social isolation in female prairie voles is a potent stressor that results in depression-like behavior and accelerated cellular aging. Importantly, oxytocin can completely prevent the negative consequences of social isolation.

Sexual Activity and Sexual Satisfaction Among Older Adults in Four European Countries

The aim of this article was to describe partnered and non-partnered sexual activity and sexual satisfaction in older men and women from Norway, Denmark, Belgium, and Portugal, and to explore sociodemographic correlates of sexual activity and satisfaction. Data were collected in 2016 using postal, anonymous questionnaires in probability samples of the population aged 60-75 years recruited by phone registers in Norway (676 men, 594 women), Denmark (530 men, 515 women), Belgium (318 men, 672 women), and Portugal (236 men, 273 women). In men, the percentage of sexually active participants in the past year ranged from 83% in Portugal to 91% in Norway. In women, the percentage of sexually active participants during the last year ranged from 61% in Belgium to 78% in Denmark. Regarding frequency of sexual intercourse activity during the past month, men in Norway, Denmark, and Belgium (23-24%) most often reported 2-3 times per month, whereas most men in Portugal (29%) reported 1-3 times per week. Masturbation was most commonly reported among Norwegian men (65%) and women (40%), and least commonly in Portugal. Concerning sexual satisfaction, across all countries, 40-60% of participants reported that they were sexually satisfied. Portuguese men and Danish women reported being most sexually satisfied. Having a partner was the most important positive predictor of sexual activity and sexual satisfaction in all subgroups except Portuguese men. In conclusion, partnered sexual activity was more frequent in the south of Europe, and solitary sexual activity more frequent in Northern Europe.

Neural mechanisms of social homeostasis

Social connections are vital to survival throughout the animal kingdom and are dynamic across the life span. There are debilitating consequences of social isolation and loneliness, and social support is increasingly a primary consideration in health care, disease prevention, and recovery. Considering social connection as an "innate need," it is hypothesized that evolutionarily conserved neural systems underlie the maintenance of social connections: alerting the individual to their absence and coordinating effector mechanisms to restore social contact. This is reminiscent of a homeostatic system designed to maintain social connection. Here, we explore the identity of neural systems regulating "social homeostasis." We review findings from rodent studies evaluating the rapid response to social deficit (in the form of acute social isolation) and propose that parallel, overlapping circuits are engaged to adapt to the vulnerabilities of isolation and restore social connection. By considering the neural systems regulating other homeostatic needs, such as energy and fluid balance, we discuss the potential attributes of social homeostatic circuitry. We reason that uncovering the identity of these circuits/mechanisms will facilitate our understanding of how loneliness perpetuates long-term disease states, which we speculate may result from sustained recruitment of social homeostatic circuits.

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

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

Loneliness in monkeys: Neuroimmune mechanisms

Loneliness, or perceived social isolation, may be evident in any group-living species, although its assessment in nonhumans provides some measurement challenges. It is well-known that loneliness in humans confers significant risk for morbidity and mortality, although mechanisms remain unclear. The authors describe a naturally-occurring model of loneliness in adult male rhesus monkeys that shows many parallels with the phenomenon in humans. Lonely monkeys (those that display high frequencies of social initiations but low frequencies of complex interaction) show elevated sympathetic nervous system activity and down regulated Type I interferon responses. Analysis of data from simian immunodeficiency virus-infected monkeys indicates that these physiological changes have functional consequences. Use of this animal model can help identify mechanisms by which loneliness impacts health.

Daily Affect and Self-Esteem in Early Adolescence: Correlates of Mean Levels and Within-Person Variability

Emotions and self-esteem are critical components of well-being and adaptation during adolescence. People differ in their average levels of affect and self-esteem, as well as in how much their affect and self-esteem fluctuate from moment to moment. Fluctuations in affect in particular have not been extensively examined in relation to adolescent-relevant variables. The present study investigates internalizing symptoms, social functioning, and overt and relational aggression as correlates of average levels and within-person variability in daily positive and negative affect (PA and NA) and self-esteem. Crucially, unique association were examined controlling for the other variables. Early adolescents (mean age 10.8 years, N = 94) completed daily diaries across four days on PA, NA, and self-esteem. They also completed general questionnaires, as did peers. Some key findings were that more internalizing symptoms were significantly associated with more variability in NA. The importance of peer relationships for adolescents' daily mean levels of PA and NA were shown. Peer-perceived social functioning was associated with less fluctuations in self-esteem. Some unexpected, non-significant, findings for aggression appeared. Finally, higher mean NA were associated with more NA fluctuations, whereas higher mean PA and self-esteem were associated with less fluctuations.

Behavioral and cardiovascular consequences of disrupted oxytocin communication in cohabitating pairs of male and female prairie voles

Negative social experiences may influence psychological and physiological health via altered central oxytocin communication. The prairie vole is valuable for investigating the potential influence of oxytocin on responses to social experiences. Prairie voles are socially monogamous, live in pairs or family groups, and respond negatively to changes in the social environment. This study investigated the hypothesis that disruptions of oxytocin in one prairie vole of a cohabitating male-female pair would alter social behavior in that specific animal; and these behavioral changes in turn would influence the untreated partner's behavior and physiology. Pharmacological antagonism of oxytocin with the receptor antagonist L-368,899 in the male prairie vole disrupted social behaviors between the male and his untreated female partner. This manipulation also negatively influenced the behavior and cardiovascular function in the untreated female partner, including increased: (a) depression-relevant behaviors in two behavioral stressors, (b) basal mean arterial pressure and heart rate, and (c) cardiovascular reactivity to the behavioral stressors. These results suggest that disruptions of oxytocin and social behavior in one animal may produce indicators of social stress in an untreated social partner. This preliminary research provides a foundation for future studies to investigate mechanisms underlying responses to social experiences in humans.

Successful aging, change in sexual interest and sexual satisfaction in couples from four European Countries

Although the importance of sexuality and physical intimacy for well-being of older adults has been recognized, the role of sexuality in successful aging (SA) has been largely neglected. Building on our previous work, here we further validated a three-dimensional model of SA and examined its associations with sexual satisfaction and change in sexual interest among older heterosexual couples (aged 60-75 years). Participants were recruited in a probability-based survey, which was carried out in 2016-2017 in four European countries. Using structural equation modeling of the Actor-Partner Interdependence, we observed significant relationships between SA and sexual satisfaction for both male and female partners across countries. Among women, their retrospectively assessed change in sexual interest over the past 10 years was consistently associated with sexual satisfaction. Partner effects were gender-specific: male partners' SA was significantly related to their female partners' change in sexual interest, which in turn was linked to male partners' sexual satisfaction. The findings point to substantial ties between successful aging and sexuality in older European couples. Taking into account the prevalent stereotypes about old age and sexuality, this study's findings can assist professionals working with aging couples.

Naturally Occurring Nonhuman Primate Models of Psychosocial Processes

Human research into psychological processes such as anxiety, depression, or loneliness typically involves accruing cases in which the phenomenon of interest is naturally occurring, and then comparing such a sample with control cases. In contrast, animal research designed to model similar processes to test mechanistic hypotheses typically involves inducing the phenomenon of interest via some exogenously (i.e., human) administered procedure. In the present review, the author proposes that naturally occurring animal models can complement induced models in understanding complex psychological phenomena. Advantages and disadvantages of naturally occurring versus induced models are described, and detailed examples of three naturally occurring models-for loneliness and health, behavioral inhibition and asthma, and social functioning and autism-are described, along with a formal program (the BioBehavioral Assessment program) at the California National Primate Research Center, that is designed to quantify variation in biobehavioral processes in infant rhesus macaques to facilitate development of naturally occurring models. It is argued that, because of the similarity in complex behavioral and psychological processes between macaques and humans, naturally occurring primate models provide a bridge between human studies and induced primate models and have the potential to identify new models for translational research.

Loneliness effects on personality

Individuals feel lonely when they perceive a discrepancy between their desired and their actually experienced quantity and quality of social relationships. Prior research has demonstrated the importance of loneliness for various health-related aspects. In the present article, we extend the existing literature on loneliness by investigating its role for predicting personality traits and their development from late adolescence to early midlife. Using data from a representative German sample ( N = 12,402) sampling individuals from three different birth cohorts, we found loneliness to predict the levels of all Big Five traits except openness five years later. The effects of loneliness on the development of neuroticism and extraversion reached statistical significance but were only marginal in terms of effect size. Furthermore, we found that a self-regulatory focus geared to the prevention of negative events mediated the effects of loneliness on later levels of the Big Five.

Loneliness predicts a preference for larger interpersonal distance within intimate space

Loneliness is thought to serve as an adaptive signal indicating the need to repair or replace salutary social connections. Accordingly, loneliness may influence preferences for interpersonal distance. If loneliness simply motivates a desire to socially reconnect, then loneliness may be associated with a preference for smaller interpersonal distances. According to the evolutionary model of loneliness, however, loneliness also signals an inadequacy of mutual aid and protection, augmenting self-preservation motives. If loneliness both increases the motivation to reconnect and increases the motivation for self-protection, then the resulting approach-avoidance conflict should produce a preference for larger interpersonal distance, at least within intimate (i.e., proximal) space. Here, we report two survey-based studies of participants’ preferences for interpersonal distance to distinguish between these competing hypotheses. In Study 1 (N = 175), loneliness predicted preferences for larger interpersonal distance within intimate space net gender, objective social isolation, anxiety, depressive symptomatology, and marital status. In Study 2 (N = 405), we replicated these results, and mediation analyses indicated that measures of social closeness could not adequately explain our findings. These studies provide compelling evidence that loneliness predicts preferences for larger interpersonal distance within intimate space, consistent with predictions from the evolutionary model of loneliness.

Loneliness Mediates the Relationship Between Pain During Intercourse and Depressive Symptoms Among Young Women

Previous research suggests that women who experience pain during intercourse also experience higher rates of depressive symptoms. Loneliness might be one factor that contributes to this relationship. We hypothesized that women who experience more severe and interfering pain during intercourse would report higher rates of loneliness and higher rates of depressive symptoms. Further, we hypothesized that loneliness would mediate the relationship between pain during intercourse and depressive symptoms. A total of 104 female participants (85.6% white, 74.03% partnered, 20.9 [3.01] years old) completed an online survey including demographic information, PROMIS Vaginal Discomfort Measure, PROMIS Depression Measure, and Revised UCLA Loneliness Scale. Pearson correlations and bootstrapped mediation analysis examined the relationships among pain during intercourse, loneliness, and depressive symptoms. Pain during intercourse, loneliness, and depressive symptoms were all significantly correlated (p < .05). Results of the mediation analysis indicated that loneliness was a significant mediator of the relationship between pain during intercourse and depressive symptoms (indirect effect = 0.077; 95% CI 0.05-0.19). After accounting for loneliness, pain during intercourse was not significantly related to depressive symptoms, suggesting that loneliness fully mediated the relationship between pain during intercourse and depressive symptoms. These findings are consistent with previous studies highlighting that pain during intercourse is related to depressive symptoms. The current study adds to that literature and suggests that more frequent and severe pain during intercourse leads to more loneliness, which then leads to increased depressive symptoms. This line of work has important implications for treating women who experience depressive symptoms and pain during intercourse.

Growing Apart: A Longitudinal Assessment of the Relation Between Post-traumatic Growth and Loneliness Among Combat Veterans

The aftermath of war-related trauma may entail psychological devastation and is typically accompanied by various deleterious phenomena. These include, but are not limited to, high rates of loneliness. However, trauma may also result in positive outcomes such as personal, spiritual, and relational prosperity, which are typically considered under the conceptual framework of post-traumatic growth (PTG). PTG may theoretically contribute to either loneliness amelioration (e.g., via increasing one's appreciation of close relationships) or exacerbation (e.g., by increasing one's sense of undergoing experiences that others do not share). Loneliness, on the other hand, may potentially hinder PTG by fostering negative social cognitions and behaviors, or otherwise lead to personal growth. The relations between the two phenomena, however, have yet to be investigated. Filling this gap, the current study examined the aforementioned potentialities by utilizing an autoregressive cross-lagged modeling strategy (ARCL) with a cohort of 260 Israeli combat veterans assessed 30, 35, and 42 years after their participation in the 1973 Yom Kippur War. Results indicated that higher rates of PTG were consistently related to higher rates of loneliness both cross-sectionally and longitudinally. Loneliness, however, did not longitudinally predict PTG rates. It is suggested that these findings may be understood in light of the observation that veterans' loneliness is primarily related to the experience of being experientially out of sync with people who have not endured war experiences. It is suggested that this experiential loneliness may include not only the negative but also the positive ramifications of undergoing such traumas (i.e., PTG). We, therefore, argue that while PTG may include authentic positive transformations it may also lead to more negative ramifications, and these should be identified and addressed by researchers and clinicians alike. Thus, as study limitations are acknowledged, clinical implications, and future research directions are suggested.

People who need people: Trait loneliness influences positive affect as a function of interpersonal context

Trait loneliness is associated with negative health consequences; understanding involved processes may elucidate its contributory role. Evolutionary and reaffiliative models associate loneliness with negative affect and dysregulated cortisol responding, while the social monitoring system model associates loneliness with heightened salience of social cues. We hypothesized that loneliness would be associated with greater negative affect and cortisol reactivity, comparing a negative-evaluative audience Trier Social Stress Test ("audience condition;" n = 55) versus a no-audience control condition (n = 69) in non-depressed young adults. Opposing hypotheses, multilevel growth curve models indicated that loneliness was not associated with negative affect or cortisol reactivity in the audience versus no-audience condition. Loneliness was, however, associated with greater positive affect reactivity in the audience versus no-audience condition. In particular, the positive affect subfacet "Interest" was heightened in the audience condition but blunted in the no-audience condition as a function of loneliness, echoing a social monitoring system model of loneliness.

Loneliness, Social Isolation, and Cardiovascular Health

SIGNIFICANCE

Social and demographic changes have led to an increased prevalence of loneliness and social isolation in modern society. Recent Advances: Population-based studies have demonstrated that both objective social isolation and the perception of social isolation (loneliness) are correlated with a higher risk of mortality and that both are clearly risk factors for cardiovascular disease (CVD). Lonely individuals have increased peripheral vascular resistance and elevated blood pressure. Socially isolated animals develop more atherosclerosis than those housed in groups.

CRITICAL ISSUES

Molecular mechanisms responsible for the increased cardiovascular risk are poorly understood. In recent reports, loneliness and social stress were associated with activation of the hypothalamic-pituitary-adrenocortical axis and the sympathetic nervous system. Repeated and chronic social stress leads to glucocorticoid resistance, enhanced myelopoiesis, upregulated proinflammatory gene expression, and oxidative stress. However, the causal role of these mechanisms in the development of loneliness-associated CVD remains unclear.

FUTURE DIRECTIONS

Elucidation of the molecular mechanisms of how CVD is induced by loneliness and social isolation requires additional studies. Understanding of the pathomechanisms is essential for the development of therapeutic strategies to prevent the detrimental effects of social stress on health. Antioxid. Redox Signal. 28, 837-851.

Depression subtyping based on evolutionary psychiatry: Proximate mechanisms and ultimate functions

Major depressive disorder constitutes one of the leading causes of disability worldwide. However, it is not a unitary disease-it is a heterogeneous syndrome, with patients differing remarkably in symptom profile, pathophysiology and treatment responsiveness. Previous attempts to subtype major depressive disorder have showed limited clinical applicability. We present a classification of major depressive disorder episodes based on the proximate mechanisms that led to the original mood change that caused the depressive episode. We identify discrete depression subtypes that are induced by: 1) infection, 2) long-term stress, 3) loneliness, 4) traumatic experience, 5) hierarchy conflict, 6) grief, 7) romantic rejection, 8) postpartum events, 9) the season, 10) chemicals, 11) somatic diseases and 12) starvation. We further examine the ultimate functions of these subtypes and show that not all types of mood changes that trigger depression are adaptive. Instead, some are clearly maladaptive and some are byproducts of other adaptations. In modern societies, low mood after adverse life events may turn into a pathological depressive state. Modern lifestyle increases susceptibility to inflammatory dysregulation and chronic stress, both of which increase the amount of proinflammatory cytokines in peripheral blood, leading to low mood and sickness behaviour. Proinflammatory cytokines may aggravate the previously adaptive short-term mood changes to a chronic maladaptive depressive state by preventing the normalization of mood after adverse life events. Subtyping depression enables an effective and intelligent long-term treatment of patients in each subtype by treating the underlying causes of depression.

Traumatization, Loneliness, and Suicidal Ideation among Former Prisoners of War: A Longitudinally Assessed Sequential Mediation Model

Although highly researched among veterans, the underlying mechanisms of suicidal ideation (SI) among former prisoners of war (ex-POWs), especially in the long-term, have rarely been investigated. Furthermore, while posttraumatic stress symptoms (PTSS) and loneliness have been individually associated with veteran SI, and both may be differentially implicated by captivity versus war traumas, the interplay between them has yet to be examined. Filling this gap, the current longitudinal study examined a hypothetical sequential model wherein war captivity, compared with combat-induced trauma, is implicated in worse PTSS, which is then implicated in worse loneliness and PTSS, which together may explain subsequent SI. Two groups of Israeli veterans of the 1973 Yom Kippur War, 163 ex-POWs and 185 matched non-captive veterans were assessed 18 (T1) and 30 (T2) years after the war. Analyses indicated that compared with war, captivity was implicated in worse PTSS, which was implicated in worse loneliness, and these worked in tandem to implicate SI. Loneliness, however, was not directly affected by the type of trauma, nor was its relation to SI linked to its implication in subsequent PTSS. These results may inform future research and clinical practice as the study underscores the importance of both PTSS and loneliness in ex-POWs' long-term SI.

Whites but Not Blacks Gain Life Expectancy from Social Contacts

Background. Recent research suggests that the health gain from economic resources and psychological assets may be systematically larger for Whites than Blacks. Aim. This study aimed to assess whether the life expectancy gain associated with social contacts over a long follow up differs for Blacks and Whites. Methods. Data came from the Americans’ Changing Lives (ACL) Study, 1986–2011. The sample was a nationally representative sample of American adults 25 and older, who were followed for up to 25 years (n = 3361). Outcome was all-cause mortality. The main predictor was social contacts defined as number of regular visits with friends, relatives, and neighbors. Baseline demographics (age and gender), socioeconomic status (education, income, and employment), health behaviors (smoking and drinking), and health (chronic medical conditions, obesity, and depressive symptoms) were controlled. Race was the focal moderator. Cox proportional hazard models were used in the pooled sample and based on race. Results. More social contacts predicted higher life expectancy in the pooled sample. A significant interaction was found between race and social contacts, suggesting that the protective effect of more social contacts is smaller for Blacks than Whites. In stratified models, more social contacts predicted an increased life expectancy for Whites but not Blacks. Conclusion. Social contacts increase life expectancy for White but not Black Americans. This study introduces social contacts as another social resource that differentially affects health of Whites and Blacks.

Loneliness is adversely associated with physical and mental health and lifestyle factors: Results from a Swiss national survey

Introduction

Loneliness is a common, emotionally distressing experience and is associated with adverse physical and mental health and an unhealthy lifestyle. Nevertheless, little is known about the prevalence of loneliness in different age groups in Switzerland. Furthermore, the existing evidence about age and gender as potential effect modifiers of the associations between loneliness, physical and mental health and lifestyle characteristics warrants further investigation. Thus, the aim of the study was to examine the prevalence of loneliness among adults in Switzerland and to assess the associations of loneliness with several physical and mental health and behavioral factors, as well as to assess the modifying effect of sex and age.

Methods

Data from 20,007 participants of the cross-sectional population-based Swiss Health Survey 2012 (SHS) were analyzed. Logistic regression analyses were used to assess associations of loneliness with physical and mental health or lifestyle characteristics (e.g. diabetes, depression, physical activity). Wald tests were used to test for interactions.

Results

Loneliness was distributed in a slight U-shaped form from 15 to 75+ year olds, with 64.1% of participants who had never felt lonely. Lonely individuals were more often affected by physical and mental health problems, such as self-reported chronic diseases (Odds ratio [OR] 1.41, 95% confidence interval [CI] 1.30–1.54), high cholesterol levels (OR 1.31, 95% CI 1.18–1.45), diabetes (OR 1.40, 95% CI 1.16–1.67), moderate and high psychological distress (OR 3.74, 95% CI 3.37–4.16), depression (OR 2.78, 95% CI 2.22–3.48) and impaired self-perceived health (OR 1.94, 95% CI 1.74–2.16). Loneliness was significantly associated with most lifestyle factors (e.g. smoking; OR 1.13, 95% 1.05–1.23). Age, but not sex, moderated loneliness’ association with several variables.

Conclusion

Loneliness is associated with poorer physical and mental health and unhealthy lifestyle, modified by age, but not by sex. Our findings illustrate the importance of considering loneliness for physical and mental health and lifestyle factors, not only in older and younger, but also in middle-aged adults. Longitudinal studies are needed in Switzerland to elucidate the causal relationships of these associations.

Reciprocal Influences Between Loneliness and Self-Centeredness: A Cross-Lagged Panel Analysis in a Population-Based Sample of African American, Hispanic, and Caucasian Adults

Loneliness has been posited to increase the motivation to repair or replace deficient social relationships and, seemingly paradoxically, to increase the implicit motivation for self-preservation. In the current research, we report a cross-lagged panel analysis of 10 waves of longitudinal data ( N = 229) on loneliness and self-centeredness (as gauged by Feeney and Collins's measure of chronic self-focus) in a representative sample of middle-aged and older adults. As predicted by the proposition that loneliness increases the implicit motivation for self-preservation, loneliness in the current year predicts self-centeredness in the subsequent year beyond what is explained by current-year demographic variables, self-centeredness, depressive symptomatology, and overall negative mood. Analyses also show that self-centeredness in the current year (net covariates) predicts loneliness in the subsequent year, a reciprocal relationship that could potentially contribute to the maintenance of loneliness. Theoretical and practical implications are discussed.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Experiential Avoidance Mediates the Association between Emotion Regulation Abilities and Loneliness

Experiential avoidance (EA) involves the unwillingness to remain in contact with aversive experiences such as painful feelings, thoughts, and emotions. EA is often associated with the development and maintenance of emotional problems. Since loneliness is characterized by negative emotions such as sadness and pessimism, which is often linked to emotional problems, this study aims to test the mediating effects of EA on the relationship between emotion regulation abilities (ERA) and loneliness in a sample of Chinese adults. Five hundred undergraduates completed questionnaires measuring EA (Acceptance and Action Questionnaire; AAQ-Ⅱ), ERA (Failure-relate action orientation; Action Control Scale, ACS-90) and loneliness (UCLA Loneliness Scale). Structural equation modeling showed that EA fully-mediated the relationship between ERA and loneliness. The findings suggest EA is a key mechanism in explaining why people with high ERA are prone to feeling lower levels of loneliness. In particular, these findings have important implications for designing effective psychological interventions for loneliness.

Neuropeptide Regulation of Social Attachment: The Prairie Vole Model

Social attachments are ubiquitous among humans and integral to human health. Although great efforts have been made to elucidate the neural underpinnings regulating social attachments, we still know relatively little about the neuronal and neurochemical regulation of social attachments. As a laboratory animal research model, the socially monogamous prairie vole (Microtus ochrogaster) displays behaviors paralleling human social attachments and thus has provided unique insights into the neural regulation of social behaviors. Research in prairie voles has particularly highlighted the significance of neuropeptidergic regulation of social behaviors, especially of the roles of oxytocin (OT) and vasopressin (AVP). This article aims to review these findings. We begin by discussing the role of the OT and AVP systems in regulating social behaviors relevant to social attachments, and thereafter restrict our discussion to studies in prairie voles. Specifically, we discuss the role of OT and AVP in adult mate attachments, biparental care, social isolation, and social buffering as informed by studies utilizing the prairie vole model. Not only do these studies offer insight into social attachments in humans, but they also point to dysregulated mechanisms in several mental disorders. We conclude by discussing these implications for human health. © 2017 American Physiological Society. Compr Physiol 7:81-104, 2017.

A developmental social neuroscience model for understanding loneliness in adolescence

Loneliness is prevalent in adolescents. Although it can be a normative experience, children and adolescents who experience loneliness are often at risk for anxiety, depression, and suicide. Research efforts have been made to identify the neurobiological basis of such distressful feelings in our social brain. In adolescents, the social brain is still undergoing significant development, which may contribute to their increased and differential sensitivity to the social environment. Many behavioral studies have shown the significance of attachment security and social skills in adolescents' interactions with the social world. In this review, we propose a developmental social neuroscience model that extends from the social neuroscience model of loneliness. In particular, we argue that the social brain and social skills are both important for the development of adolescents' perceived loneliness and that adolescents' familial attachment sets the baseline for neurobiological development. By reviewing the related behavioral and neuroimaging literature, we propose a developmental social neuroscience model to explain the heightened perception of loneliness in adolescents using social skills and attachment style as neurobiological moderators. We encourage future researchers to investigate adolescents' perceived social connectedness from the developmental neuroscience perspective.

Challenges to the Pair Bond: Neural and Hormonal Effects of Separation and Reunion in a Monogamous Primate

Social monogamy at its most basic is a group structure in which two adults form a unit and share a territory. However, many socially monogamous pairs display attachment relationships known as pair bonds, in which there is a mutual preference for the partner and distress upon separation. The neural and hormonal basis of this response to separation from the adult pair mate is under-studied. In this project, we examined this response in male titi monkeys (Callicebus cupreus), a socially monogamous New World primate. Males underwent a baseline scan, a short separation (48 h), a long separation (approximately 2 weeks), a reunion with the female pair mate and an encounter with a female stranger (with nine males completing all five conditions). Regional cerebral glucose metabolism was measured via positron emission tomography (PET) imaging using [18F]-fluorodeoxyglucose (FDG) co-registered with structural magnetic resonance imaging (MRI), and region of interest (ROI) analysis was carried out. In addition, plasma was collected and assayed for cortisol, oxytocin (OT), vasopressin (AVP), glucose and insulin concentrations. Cerebrospinal fluid (CSF) was collected and assayed for OT and AVP. We used generalized estimating equations (GEE) to examine significant changes from baseline. Short separations were characterized by decreases in FDG uptake, in comparison to baseline, in the lateral septum (LS), ventral pallidum (VP), paraventricular nucleus of the hypothalamus (PVN), periaqueductal gray (PAG), and cerebellum, as well as increases in CSF OT, and plasma cortisol and insulin. Long separations differed from baseline in reduced FDG uptake in the central amygdala (CeA), reduced whole brain FDG uptake, increased CSF OT and increased plasma insulin. The response on encounter with a stranger female depended on whether or not the male had previously reproduced with his pair mate, suggesting that transitions to fatherhood contribute to the neurobiology underlying response to a novel female. Reunion with the partner appeared to stimulate coordinated release of central and peripheral OT. The observed changes suggest the involvement of OT and AVP systems, as well as limbic and striatal areas, during separation and reunion from the pair mate.

Perceived social isolation, evolutionary fitness and health outcomes: a lifespan approach

Sociality permeates each of the fundamental motives of human existence and plays a critical role in evolutionary fitness across the lifespan. Evidence for this thesis draws from research linking deficits in social relationship--as indexed by perceived social isolation (i.e. loneliness)--with adverse health and fitness consequences at each developmental stage of life. Outcomes include depression, poor sleep quality, impaired executive function, accelerated cognitive decline, unfavourable cardiovascular function, impaired immunity, altered hypothalamic pituitary-adrenocortical activity, a pro-inflammatory gene expression profile and earlier mortality. Gaps in this research are summarized with suggestions for future research. In addition, we argue that a better understanding of naturally occurring variation in loneliness, and its physiological and psychological underpinnings, in non-human species may be a valuable direction to better understand the persistence of a 'lonely' phenotype in social species, and its consequences for health and fitness.

Social instability and immunity in rhesus monkeys: the role of the sympathetic nervous system

Social instability can adversely affect endocrine, immune and health outcomes, and recent evidence suggests that the sympathetic nervous system (SNS) might mediate these effects. We conducted two studies with adult male rhesus monkeys (Macaca mulatta) to understand how social conditions affect measures of SNS activity and immune function. In Experiment 1, animals were socialized in stable social conditions, then were switched to unstable (stressful) social conditions, then were returned to stable conditions. Analysis revealed quadratic effects for measures of behaviour, urinary metabolites of epinephrine and norepinephrine, and expression of immune response genes: as expected, social instability adversely impacted most measures, and the effects remediated upon re-imposition of stable conditions. Cortisol levels were unaffected. In Experiment 2, we used the sympathomimetic drug methamphetamine to challenge the SNS; animals also underwent socialization in stable or unstable groups. Surprisingly, while methamphetamine elevated plasma catecholamines, responses in lymph nodes tracked the social, and not the drug, condition: social instability upregulated the density of SNS fibres in lymph nodes and downregulated Type I interferon gene expression. Together, these results indicate that the SNS is extremely sensitive to social conditions; full understanding of the adverse effects of social instability on health should therefore incorporate measures of this health-relevant system.