Communication of health in experimentally sick men and women: A pilot study

When and Why People Conceal Infectious Disease

People sick with infectious illnesses face negative social outcomes, like exclusion, and may take steps to conceal their illnesses from others. In 10 studies of past, current, and projected illness, we examined the prevalence and predictors of infection concealment in adult samples of U.S. university students, health-care employees, and online crowdsourced workers (total N = 4,110). About 75% reported concealing illness in interpersonal interactions, possibly placing others in harm's way. Concealment motives were largely social (e.g., wanting to attend events like parties) and achievement oriented (e.g., completing work objectives). Disease characteristics, including potential harm and illness immediacy, also influenced concealment decisions. People imagining harmful (vs. mild) infections concealed illness less frequently, whereas participants who were actually sick concealed frequently regardless of illness harm, suggesting state-specific biases underlying concealment decisions. Disease concealment appears to be a widely prevalent behavior by which concealers trade off risks to others in favor of their own goals, creating potentially important public-health consequences.

Typhoid vaccine does not impact feelings of social connection or social behavior in a randomized crossover trial among middle-aged female breast cancer survivors

BACKGROUND

Inflammation can have social consequences, which may be relevant to inflammation's link with depression. The current study tests whether a typhoid vaccine increases feelings of social disconnection and avoidance behavior.

METHOD

In two full-day visits at least three weeks apart, 172 postmenopausal breast cancer survivors (Stage I-IIIA) each received a typhoid capsular polysaccharide vaccination and a saline placebo injection in a random sequence. Blood was drawn prior to the injection, as well as every 90 min thereafter for 8 h to assess the inflammatory response (interleukin-6, IL-6; interleukin-1 receptor antagonist, IL-1Ra). At both visits, women completed the Social Connection Scale at 0 and 8.5 h post-vaccination as well as implicit and explicit social avoidance tasks at 7 h post-vaccination.

RESULTS

The typhoid vaccine triggered rises in both inflammatory markers (ps < 0.01), but it did not impact feelings of social connection (p = .32), or performance on the implicit (p = .34) or explicit tasks (p = .37). Inflammatory rises did not predict feelings of social connection (ps > 0.64) or performance on explicit (ps > 0.73) or implicit (ps > 0.88) social avoidance tasks.

CONCLUSION

Milder inflammatory stimuli may not affect social processes. Higher levels of inflammation or, relatedly, more sickness symptoms may be necessary to recapitulate prior findings of social avoidance.

The Effects of Cold Exposure Training and a Breathing Exercise on the Inflammatory Response in Humans: A Pilot Study

OBJECTIVE

We previously showed that a training intervention comprising a combination of meditation, exposure to cold, and breathing exercises enables voluntary activation of the sympathetic nervous system, reflected by profoundly increased plasma epinephrine levels, and subsequent attenuation of the lipopolysaccharide (LPS)-induced inflammatory response. Several elements of the intervention may contribute to these effects, namely, two different breathing exercises (either with or without prolonged breath retention) and exposure to cold. We determined the contribution of these different elements to the observed effects.

METHODS

Forty healthy male volunteers were randomized to either a short or an extensive training in both breathing exercises by either the creator of the training intervention or an independent trainer. The primary outcome was plasma epinephrine levels. In a subsequent study, 48 healthy male volunteers were randomized to cold exposure training, training in the established optimal breathing exercise, a combination of both, or no training. These 48 participants were subsequently intravenously challenged with 2 ng/kg LPS. The primary outcome was plasma cytokine levels.

RESULTS

Both breathing exercises were associated with an increase in plasma epinephrine levels, which did not vary as a function of length of training or the trainer (F(4,152) = 0.53, p = .71, and F(4,152) = 0.92, p = .46, respectively). In the second study, the breathing exercise also resulted in increased plasma epinephrine levels. Cold exposure training alone did not relevantly modulate the LPS-induced inflammatory response (F(8,37) = 0.60, p = .77), whereas the breathing exercise led to significantly enhanced anti-inflammatory and attenuated proinflammatory cytokine levels (F(8,37) = 3.80, p = .002). Cold exposure training significantly enhanced the immunomodulatory effects of the breathing exercise (F(8,37) = 2.57, p = .02).

CONCLUSIONS

The combination of cold exposure training and a breathing exercise most potently attenuates the in vivo inflammatory response in healthy young males. Our study demonstrates that the immunomodulatory effects of the intervention can be reproduced in a standardized manner, thereby paving the way for clinical trials.Trial Registration:ClinicalTrials.gov identifiers: NCT02417155 and NCT03240497.

Networks, cultures, and institutions: Toward a social immunology

This paper calls for increased attention to the ways in which immune function – including its behavioral aspects – are responsive to social contexts at multiple levels. Psychoneuroimmunology has demonstrated that the quantity and quality of social connections can affect immune responses, while newer research is finding that sickness temporarily affects these same social networks and that some aspects of culture can potentially “get under the skin” to affect inflammatory responses. Social immunology, the research framework proposed here, unifies these findings and also considers the effects of structural factors – that is, a society's economic, political, and environmental landscape – on exposure to pathogens and subsequent immune responses. As the COVID-19 pandemic has highlighted, a holistic understanding of the effects of social contexts on the patterning of morbidity and mortality is critically important. Social immunology provides such a framework and can highlight important risk factors related to impaired immune function.

Back to the future of psychoneuroimmunology: Studying inflammation-induced sickness behavior

What do we know about sickness behavior? In this article, I guide you through some of the complexity of sickness behavior occurring after an immune challenge. I highlight the many features of behavioral and affective changes induced during experimental endotoxemia in humans, and describe how little we know about many of these features. I argue that we need to dismantle the components of inflammation-induced sickness behavior, and study each component in detail. I also point out the large inter-individual differences in inflammation-induced behavioral and affective changes, and the fact that psychosocial factors likely interact with inflammation to shape inflammation-induced sickness behavior. PNI clearly lacks investigations of the vulnerability and resilient factors underlying the inter-individual variability in sickness behavior. Throughout the article, I base my argument on my published articles, and provide concrete examples from my experience and the data that I have collected over the past 10 years. Given the relevance of inflammation-induced sickness behavior for inflammation-associated depression and for how people react to infections, I encourage current and future psychoneuroimmunologists to return towards basic science of sickness behavior.

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Inflammation-related sickness behavior is relevant for inflammation-associated depression

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The many features of sickness behavior should be investigated in detail

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There are large inter-individual variability in sickness behavior

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Vulnerability and resilient factors predicting sickness responses are little known

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I call for a return towards basic science of sickness behavior.

Beyond social withdrawal: New perspectives on the effects of inflammation on social behavior

Decades of research in animals and humans show that inflammation is an important regulator of social behavior. While much research in this area has concluded that inflammation causes a withdrawal from social interaction, closer examination of the literature reveals that the effects of inflammation on social behavior are much more nuanced. Indeed, while many studies do show that increases in inflammation lead to social withdrawal, other studies show the exact opposite, finding that inflammation leads to an increase in social approach behavior. Critically, whether an organism withdraws or approaches when inflamed may depend on the whether the target of the behavior is a close other or a stranger. In the present paper, we review both animal research and our initial research in humans that has utilized experimental manipulations of inflammation and examined their effects on social approach behavior. We argue, based on complementary theoretical perspectives and supporting evidence from the literature, that there are three critical next steps for translational work examining the effects of inflammation on social behavior: (1) We need to study actual social behavior, as expressed toward both close others and strangers; (2) We should examine not just the social behavior of the inflamed individual, but also the behavior of others interacting with an inflamed individual; and (3) We must consider the relative increases in inflammation (i.e., higher vs. lower) as a contributor to social withdrawal vs. approach. Ultimately, we urge the field to move beyond a singular focus on inflammation and social withdrawal so that we can develop a more comprehensive understanding of the effects of inflammation on a variety of social behaviors.

Signaling sickness: the role of recalled sickness behavior and psychosocial factors in shaping communication style

Background and objectives

Active infection results in several outward signs in humans, including visible symptoms, changes in behavior and possible alterations in skin color and gait. A potential adaptive function of these indicators is to signal distress and elicit care from close others. We hypothesized that sickness behavior, a suite of stereotypical changes in mood and behavior, also serves to communicate health status to others. We further hypothesized that such outward signals/cues of health status would vary based on context and sociocultural norms.

Methodology

We explored self-reported, recalled sickness behavior, communication style, demographics and theoretically relevant cultural factors in a large national US sample (n = 1259) using multinomial probit regressions.

Results

In accordance with predictions, relatively few participants were willing to talk or complain about sickness to strangers. Self-reported, recalled sickness behavior was associated with some communication styles but attention received from others was more consistently associated with potential signaling. Several cultural factors, including stoicism and traditional machismo, were also associated with different sickness signaling styles.

Conclusions and implications

These preliminary, self-reported data lend some tentative support to the sickness behavior signaling hypothesis, though experimental or observational support is needed. The role of cultural norms in shaping how such signals are transmitted and received also deserves further attention as they may have important implications for disease transmission.

Lay Summary

Evolutionary medicine hypothesizes that signs and symptoms of infectious disease—including sickness behavior—have adaptive functions, one of which might be to reliably signal one’s health status to others. Our results suggest that evolved signals like these are likely shaped by cultural factors.

Infectious diseases and social distancing in nature

Spread of contagious pathogens critically depends on the number and types of contacts between infectious and susceptible hosts. Changes in social behavior by susceptible, exposed, or sick individuals thus have far-reaching downstream consequences for infectious disease spread. Although "social distancing" is now an all too familiar strategy for managing COVID-19, nonhuman animals also exhibit pathogen-induced changes in social interactions. Here, we synthesize the effects of infectious pathogens on social interactions in animals (including humans), review what is known about underlying mechanisms, and consider implications for evolution and epidemiology.

Sickness and the Social Brain: Love in the Time of COVID

As a highly social species, inclusion in social networks and the presence of strong social bonds are critical to our health and well-being. Indeed, impaired social functioning is a component of numerous neuropsychiatric disorders including depression, anxiety, and substance use disorder. During the current COVID-19 pandemic, our social networks are at risk of fracture and many are vulnerable to the negative consequences of social isolation. Importantly, infection itself leads to changes in social behavior as a component of "sickness behavior." Furthermore, as in the case of COVID-19, males and females often differ in their immunological response to infection, and, therefore, in their susceptibility to negative outcomes. In this review, we discuss the many ways in which infection changes social behavior-sometimes to the benefit of the host, and in some instances for the sake of the pathogen-in species ranging from eusocial insects to humans. We also explore the neuroimmune mechanisms by which these changes in social behavior occur. Finally, we touch upon the ways in which the social environment (group living, social isolation, etc.) shapes the immune system and its ability to respond to challenge. Throughout we emphasize how males and females differ in their response to immune activation, both behaviorally and physiologically.

Comparison of bacterial lipopolysaccharide-induced sickness behavior in rodents and humans: Relevance for symptoms of anxiety and depression

Increasing evidence from animal and human studies suggests that inflammation may be involved in mood disorders. Sickness behavior and emotional changes induced by experimental inflammatory stimuli have been extensively studied in humans and rodents to better understand the mechanisms underlying inflammation-driven mood alterations. However, research in animals and humans have remained compartmentalized and a comprehensive comparison of inflammation-induced sickness and depressive-like behavior between rodents and humans is lacking. Thus, here, we highlight similarities and differences in the effects of bacterial lipopolysaccharide administration on the physiological (fever and cytokines), behavioral and emotional components of the sickness response in rodents and humans, and discuss the translational challenges involved. We also emphasize the differences between observable sickness behavior and subjective sickness reports, and advocate for the need to obtain both subjective reports and objective measurements of sickness behavior in humans. We aim to provide complementary insights for translational clinical and experimental research on inflammation-induced behavioral and emotional changes, and their relevance for mood disorders such as depression.

Properties of the Sickness Questionnaire in an Australian sample with chronic medically unexplained symptoms

Sickness behavior including malaise, fatigue and increased pain sensitivity is thought to be adaptive and facilitate recovery from disease. However, it may also reduce functioning and health if symptoms persists, which is why validated instruments for its assessment are needed. We evaluated the English translation of the Sickness Questionnaire (SicknessQ) in an Australian population of 156 participants with high level of persistent musculoskeletal pain and/or gastrointestinal symptoms without an organic explanation. The SicknessQ total score had an adequate model fit and no other models were found to fit data better. The SicknessQ correlated most strongly with fatigue, stress, anxiety and depression, which explained 62% of the variance in SicknessQ, but not with physical functioning. The mean score (8.9; 95 %CI: 8.0-9.8) was in between those previously reported in a general population sample and in primary care patients. In conclusion, the evaluation of the English version of the SicknessQ in an Australian sample with significant, chronic unexplained medical symptoms supports the use of the English version of the total SicknessQ score as an overall measure of sickness behavior.

Sex differences in how inflammation affects behavior: What we can learn from experimental inflammatory models in humans

Human models demonstrate that experimental activation of the innate immune system has profound effects on brain activation and behavior, inducing fatigue, worsened mood and pain sensitivity. It has been proposed that inflammation is a mechanism involved in the etiology and maintenance of depression, chronic pain and long-term fatigue. These diseases show a strong female overrepresentation, suggesting that a better understanding of sex differences in how inflammation drives behavior could help the development of individualized treatment interventions. For this purpose, we here review sex differences in studies using experimental inflammatory models to investigate changes in brain activity and behavior. We suggest a model in which inflammation accentuates sex differences in brain networks and pre-existing vulnerability factors. This effect could render women more vulnerable to the detrimental effects of immune-to-brain communication over time. We call for systematic and large scale investigations of vulnerability factors for women in the behavioral response to inflammation.