Social regulation of leukocyte homeostasis: the role of glucocorticoid sensitivity

Loneliness matters: a theoretical and empirical review of consequences and mechanisms

As a social species, humans rely on a safe, secure social surround to survive and thrive. Perceptions of social isolation, or loneliness, increase vigilance for threat and heighten feelings of vulnerability while also raising the desire to reconnect. Implicit hypervigilance for social threat alters psychological processes that influence physiological functioning, diminish sleep quality, and increase morbidity and mortality. The purpose of this paper is to review the features and consequences of loneliness within a comprehensive theoretical framework that informs interventions to reduce loneliness. We review physical and mental health consequences of loneliness, mechanisms for its effects, and effectiveness of extant interventions. Features of a loneliness regulatory loop are employed to explain cognitive, behavioral, and physiological consequences of loneliness and to discuss interventions to reduce loneliness. Loneliness is not simply being alone. Interventions to reduce loneliness and its health consequences may need to take into account its attentional, confirmatory, and memorial biases as well as its social and behavioral effects.

Elevating the perspective on human stress genomics

Functional genomics strategies have been slow to penetrate research on human stress and coping, but recent conceptual advances have yielded a raft of new findings relating social and psychological conditions to broad alterations in human gene expression. This article reviews the field of human stress genomics, analyzes some of the conceptual and technical issues that initially hampered its progress, and outlines an abstractionist approach to genomic data analysis that has revealed a surprisingly consistent pattern of human transcriptional responses to diverse types of socio-environmental adversity. This field is now poised for another round of significant advances as research begins to incorporate the effects of DNA polymorphism, target a broader array of healthy and diseased tissues, and identify general teleologic and regulatory themes by pooling results over a growing body of studies analyzing the human transcriptional response to stress.

Moderating effect of apolipoprotein genotype on loneliness leading to depressive symptoms in Chinese older adults

OBJECTIVE

Depressive symptoms, which are both common and heritable, are important indicators of the extent of general well-being and health in old age. Identifying risk factors for depressive symptoms may lead to improved intervention and effective prevention. Both the presence of the apolipoprotein (APOE) genotype and loneliness are associated with later life symptoms of depression, and all three share a neuroendocrine signature, namely altered activity in the hypothalamic-pituitary-adrenal axis. The authors expected a positive association of loneliness with depressive symptoms, a negative link between APOE epsilon2 with depressive symptoms, and a significant genotype-environment interaction between loneliness (the social environment) and APOE epsilon2 on symptoms of depression.

DESIGN

This was a cross-sectional observational study.

SETTING AND PARTICIPANTS

A population-based sample of 979 Chinese people from Taiwan aged 54 years and older was examined.

MEASUREMENTS

A short-form of the Center for Epidemiologic Studies of Depression Scale was used and the genotype of APOE was obtained.

RESULTS

The interaction between loneliness and APOE epsilon2 was found to be negatively associated with depressive symptoms in adjusted regression models. Loneliness was also positively correlated with symptoms of depression.

CONCLUSIONS

These data suggest that the APOE epsilon2 genotype decreases vulnerability to symptoms of depression in the presence of a social stressor, namely loneliness in this case, and has implications for the enhancement of well-being among older adults. Future studies are needed to delineate the mechanism underlying this gene-environment interaction.

Close relationships, inflammation, and health

Different aspects of personal relationships including social integration, social support, and social conflict have been related to inflammation. This article summarizes evidence linking the quality and quantity of relationships with gene expression, intracellular signaling mechanisms, and inflammatory biomarkers, and highlights the biological and psychological pathways through which close relationships impact inflammatory responses. Relationship conflict and lower social support can effectively modulate proinflammatory cytokine secretion both directly (via CNS/neural/endocrine/immune biobehavioral pathways), and indirectly, by promoting depression, emotional stress responses, and detrimental health behaviors. Accordingly, thorough assessments of health behaviors and attention to key methodological issues are necessary to identify the contributions of relationships to inflammation, and thus we highlight procedural issues to be considered in the design of studies. Despite some notable methodological challenges, the evidence suggests that learning more about how close relationships influence inflammation will provide important new insights into the ways that relationships impact health.

Perceived social isolation and cognition

Social species, from Drosophila melanogaster to Homo sapiens, fare poorly when isolated. Homo sapiens, an irrepressibly meaning-making species, are, in normal circumstances, dramatically affected by perceived social isolation. Research indicates that perceived social isolation (i.e. loneliness) is a risk factor for, and may contribute to, poorer overall cognitive performance, faster cognitive decline, poorer executive functioning, increased negativity and depressive cognition, heightened sensitivity to social threats, a confirmatory bias in social cognition that is self-protective and paradoxically self-defeating, heightened anthropomorphism and contagion that threatens social cohesion. These differences in attention and cognition impact on emotions, decisions, behaviors and interpersonal interactions that can contribute to the association between loneliness and cognitive decline and between loneliness and morbidity more generally.

Social stress desensitizes lymphocytes to regulation by endogenous glucocorticoids: insights from in vivo cell trafficking dynamics in rhesus macaques

OBJECTIVE

To determine whether chronic social stress can desensitize leukocytes to normal physiologic regulation by endogenous glucocorticoids.

METHODS

We analyzed the longitudinal relationship between plasma cortisol levels and peripheral blood lymphocyte counts over 16 monthly assessments in 18 rhesus macaques randomized to recurrent social encounters with a stable set of conspecifics or continually varying social partners (unstable socialization).

RESULTS

Animals socialized under stable conditions showed the expected inverse relationship between plasma cortisol concentrations and circulating lymphocyte frequencies. That relationship was significantly attenuated in animals subject to unstable social conditions. Differences in leukocyte redistributional sensitivity to endogenous glucocorticoids emerged within the first week of differential socialization, persisted throughout the 60-week study period, and were correlated with other measures of glucocorticoid desensitization (blunted hypothalamic-pituitary-adrenal (HPA) axis response to acute stress and redistributional response to dexamethasone challenge). Effects of unstable social conditions on leukocyte sensitivity to cortisol regulation were not related to physical aggression.

CONCLUSION

Chronic social stress can impair normal physiologic regulation of leukocyte function by the HPA axis in ways that may contribute to the increased physical health risks associated with social adversity.

Health psychology: developing biologically plausible models linking the social world and physical health

Research over the past several decades has documented psychosocial influences on the development and progression of several major medical illnesses. The field is now increasingly focused on identifying the biological and behavioral mechanisms underlying these effects. This review takes stock of the knowledge accumulated in the biological arena to date and highlights conceptual and methodological approaches that have proven especially productive. It emphasizes the value of a disease-centered approach that "reverse engineers" adverse health outcomes into their specific biological determinants and then identifies psychologically modulated neuroendocrine and immunologic dynamics that modulate those pathological processes at the cellular and molecular levels.

Psychobiological responses to social threat: evolution of a psychological model in psychoneuroimmunology

There exists a bidirectional network of interactions between the central nervous system, the endocrine system and the immune system. The existence of these pathways allows stressful life experience to impact the immune system with important implications for health. One powerful elicitor of changes in the autonomic, endocrine and immune systems is threat to social status. This review describes the development of a human model of social status threat that specifies a set of contextual, psychological and biological pathways that may underlie the health consequences of threats to social status and regard. The role of cognitive processes in shaping the physiological response to the social world will be emphasized.