Neurobiology and systems biology of stress resilience.

Stress resilience is the phenomenon that some people maintain their mental health despite exposure to adversity or show only temporary impairments followed by quick recovery. Resilience research attempts to unravel the factors and mechanisms that make resilience possible and to harness its insights for the development of preventative interventions in individuals at risk for acquiring stress-related dysfunctions. Biological resilience research has been lagging behind the psychological and social sciences but has seen a massive surge in recent years. At the same time, progress in this field has been hampered by methodological challenges related to finding suitable operationalizations and study designs, replicating findings, and modeling resilience in animals. We embed a review of behavioral, neuroimaging, neurobiological, and systems biological findings in adults in a critical methods discussion. We find preliminary evidence that hippocampus-based pattern separation and prefrontal-based cognitive control functions protect against the development of pathological fears in the aftermath of singular, event-type stressors [as found in fear-related disorders, including simpler forms of posttraumatic stress disorder (PTSD)] by facilitating the perception of safety. Reward system-based pursuit and savoring of positive reinforcers appear to protect against the development of more generalized dysfunctions of the anxious-depressive spectrum resulting from more severe or longer-lasting stressors (as in depression, generalized or comorbid anxiety, or severe PTSD). Links between preserved functioning of these neural systems under stress and neuroplasticity, immunoregulation, gut microbiome composition, and integrity of the gut barrier and the blood-brain barrier are beginning to emerge. On this basis, avenues for biological interventions are pointed out.

DNA methylation signatures of early-life adversity are exposure-dependent in wild baboons.

The early-life environment can profoundly shape the trajectory of an animal's life, even years or decades later. One mechanism proposed to contribute to these early-life effects is DNA methylation. However, the frequency and functional importance of DNA methylation in shaping early-life effects on adult outcomes is poorly understood, especially in natural populations. Here, we integrate prospectively collected data on fitness-associated variation in the early environment with DNA methylation estimates at 477,270 CpG sites in 256 wild baboons. We find highly heterogeneous relationships between the early-life environment and DNA methylation in adulthood: aspects of the environment linked to resource limitation (e.g., low-quality habitat, early-life drought) are associated with many more CpG sites than other types of environmental stressors (e.g., low maternal social status). Sites associated with early resource limitation are enriched in gene bodies and putative enhancers, suggesting they are functionally relevant. Indeed, by deploying a baboon-specific, massively parallel reporter assay, we show that a subset of windows containing these sites are capable of regulatory activity, and that, for 88% of early drought-associated sites in these regulatory windows, enhancer activity is DNA methylation-dependent. Together, our results support the idea that DNA methylation patterns contain a persistent signature of the early-life environment. However, they also indicate that not all environmental exposures leave an equivalent mark and suggest that socioenvironmental variation at the time of sampling is more likely to be functionally important. Thus, multiple mechanisms must converge to explain early-life effects on fitness-related traits.

The adaptive stochasticity hypothesis: Modeling equifinality, multifinality, and adaptation to adversity.

Neural phenotypes are the result of probabilistic developmental processes. This means that stochasticity is an intrinsic aspect of the brain as it self-organizes over a protracted period. In other words, while both genomic and environmental factors shape the developing nervous system, another significant-though often neglected-contributor is the randomness introduced by probability distributions. Using generative modeling of brain networks, we provide a framework for probing the contribution of stochasticity to neurodevelopmental diversity. To mimic the prenatal scaffold of brain structure set by activity-independent mechanisms, we start our simulations from the medio-posterior neonatal rich club (Developing Human Connectome Project, n = 630). From this initial starting point, models implementing Hebbian-like wiring processes generate variable yet consistently plausible brain network topologies. By analyzing repeated runs of the generative process (>107 simulations), we identify critical determinants and effects of stochasticity. Namely, we find that stochastic variation has a greater impact on brain organization when networks develop under weaker constraints. This heightened stochasticity makes brain networks more robust to random and targeted attacks, but more often results in non-normative phenotypic outcomes. To test our framework empirically, we evaluated whether stochasticity varies according to the experience of early-life deprivation using a cohort of neurodiverse children (Centre for Attention, Learning and Memory; n = 357). We show that low-socioeconomic status predicts more stochastic brain wiring. We conclude that stochasticity may be an unappreciated contributor to relevant developmental outcomes and make specific predictions for future research.

Multigenerational adversity impacts on human gut microbiome composition and socioemotional functioning in early childhood.

Adversity exposures in the prenatal and postnatal period are associated with an increased risk for psychopathology, which can be perpetuated across generations. Nonhuman animal research highlights the gut microbiome as a putative biological mechanism underlying such generational risks. In a sample of 450 mother-child dyads living in Singapore, we examined associations between three distinct adversity exposures experienced across two generations-maternal childhood maltreatment, maternal prenatal anxiety, and second-generation children's exposure to stressful life events-and the gut microbiome composition of second-generation children at 2 y of age. We found distinct differences in gut microbiome profiles linked to each adversity exposure, as well as some nonaffected microbiome features (e.g., beta diversity). Remarkably, some of the microbial taxa associated with concurrent and prospective child socioemotional functioning shared overlapping putative functions with those affected by adversity, suggesting that the intergenerational transmission of adversity may have a lasting impact on children's mental health via alterations to gut microbiome functions. Our findings open up a new avenue of research into the underlying mechanisms of intergenerational transmission of mental health risks and the potential of the gut microbiome as a target for intervention.

Transcriptional signatures of early-life stress and antidepressant treatment efficacy.

Individuals with a history of early-life stress (ELS) tend to have an altered course of depression and lower treatment response rates. Research suggests that ELS alters brain development, but the molecular changes in the brain following ELS that may mediate altered antidepressant response have not been systematically studied. Sex and gender also impact the risk of depression and treatment response. Here, we leveraged existing RNA sequencing datasets from 1) blood samples from depressed female- and male-identifying patients treated with escitalopram or desvenlafaxine and assessed for treatment response or failure; 2) the nucleus accumbens (NAc) of female and male mice exposed to ELS and/or adult stress; and 3) the NAc of mice after adult stress, antidepressant treatment with imipramine or ketamine, and assessed for treatment response or failure. We find that transcriptomic signatures of adult stress after a history of ELS correspond with transcriptomic signatures of treatment nonresponse, across species and multiple classes of antidepressants. Transcriptomic correspondence with treatment outcome was stronger among females and weaker among males. We next pharmacologically tested these predictions in our mouse model of early-life and adult social defeat stress and treatment with either chronic escitalopram or acute ketamine. Among female mice, the strongest predictor of behavior was an interaction between ELS and ketamine treatment. Among males, however, early experience and treatment were poor predictors of behavior, mirroring our bioinformatic predictions. These studies provide neurobiological evidence for molecular adaptations in the brain related to sex and ELS that contribute to antidepressant treatment response.

Neuroendocrine mechanisms in the links between early life stress, affect, and youth substance use: A conceptual model for the study of sex and gender differences.

Early life stress (ELS) is defined as an acute or chronic stressor that negatively impacts a child's development. ELS is associated with substance use and mental health problems. This narrative literature review focuses on sex and gender differences in the effects of ELS on 1) adolescent neuroendocrine development; 2) pubertal brain maturation; and 3) development of internalizing symptoms and subsequent substance use. We posit that ELS may generate larger hormonal dysregulation in females than males during puberty, increasing internalizing symptoms and substance use. Future research should consider sex and gender differences in neuroendocrine developmental processes when studying the link between ELS and negative health outcomes.

Can you remember silence? Epigenetic memory and reversibility as a site of intervention.

Just over 20 years ago, molecular biologists Leonie Ringrose and Renato Paro published an article with a provocative title, "Remembering Silence", in BioEssays. The article focused on how epigenetic elements could return to their silent state, operationally defined as their epigenetic status before their modulation by experimental or environmental factors. Though Ringrose and Paro's article was on fruit flies and factors affecting embryological growth, the article asked a question of considerable importance to rapidly expanding research in neuroepigenetics on the correlation between trauma and neuropsychiatric risk: If you experience a traumatic event and, as a result, acquire an epigenetic trait that is considered pathological, can you free yourself of that trait? Ultimately, we are interested in how a return to silence is envisioned in neuroepigenetics research, how interventions purported to bring about that silence might function, and what this might mean for people who live in the aftermath of trauma.

Reactivation of Early-Life Stress-Sensitive Neuronal Ensembles Contributes to Lifelong Stress Hypersensitivity.

Early-life stress (ELS) is one of the strongest lifetime risk factors for depression, anxiety, suicide, and other psychiatric disorders, particularly after facing additional stressful events later in life. Human and animal studies demonstrate that ELS sensitizes individuals to subsequent stress. However, the neurobiological basis of such stress sensitization remains largely unexplored. We hypothesized that ELS-induced stress sensitization would be detectable at the level of neuronal ensembles, such that cells activated by ELS would be more reactive to adult stress. To test this, we leveraged transgenic mice to genetically tag, track, and manipulate experience-activated neurons. We found that in both male and female mice, ELS-activated neurons within the nucleus accumbens (NAc), and to a lesser extent the medial prefrontal cortex, were preferentially reactivated by adult stress. To test whether reactivation of ELS-activated ensembles in the NAc contributes to stress hypersensitivity, we expressed hM4Dis receptor in control or ELS-activated neurons of pups and chemogenetically inhibited their activity during experience of adult stress. Inhibition of ELS-activated NAc neurons, but not control-tagged neurons, ameliorated social avoidance behavior following chronic social defeat stress in males. These data provide evidence that ELS-induced stress hypersensitivity is encoded at the level of corticolimbic neuronal ensembles.SIGNIFICANCE STATEMENT Early-life stress enhances sensitivity to stress later in life, yet the mechanisms of such stress sensitization are largely unknown. Here, we show that neuronal ensembles in corticolimbic brain regions remain hypersensitive to stress across the life span, and quieting these ensembles during experience of adult stress rescues stress hypersensitivity.

Do Adverse Childhood Experiences Modify the Association Between Disaster-Related Trauma and Cognitive Disability?

Identifying subpopulations that are particularly vulnerable to long-term adverse health consequences of disaster-related trauma is needed. We examined whether adverse childhood experiences (ACEs) potentiate the association between disaster-related trauma and subsequent cognitive disability among older adult disaster survivors. Data were from a prospective cohort study of older adults who survived the 2011 Great East Japan Earthquake. The baseline survey pre-dated the disaster by 7 months. We included participants who completed follow-up surveys (2013 and 2016) and did not have a cognitive disability before the disaster (n = 602). Disaster-related traumas (i.e., home loss, loss of friends or pets) and ACEs were retrospectively assessed in 2013. Cognitive disability levels in 2016 were objectively assessed. After adjusting for pre-disaster characteristics using a machine learning-based estimation approach, home loss (0.19, 95% confidence interval (CI): 0.09, 0.28) was, on average, associated with greater cognitive disability. Among individuals with ACEs, home loss was associated with even higher cognitive disability levels (0.64, 95% CI: 0.24, 1.03). Losses of friends (0.18, 95% CI: 0.05, 0.32) and pets (0.13, 95% CI: 0.02, 0.25) were associated with higher cognitive disability levels only among those with ACEs. Our findings suggest that individuals with a history of ACEs may be particularly vulnerable to adverse health consequences related to disasters.

A hypothetical intervention to reduce inequities in anxiety for Multiracial people: simulating an intervention on childhood adversity.

Multiracial people report higher mean Adverse Childhood Experiences (ACEs) scores and prevalence of anxiety than other racial groups. Studies using statistical interactions to estimate racial differences in ACEs-anxiety associations do not show stronger associations for Multiracial people. Using data from Waves 1 (1995-97) through 4 (2008-09) of the National Longitudinal Study of Adolescent to Adult Health (Add Health), we simulated a stochastic intervention over 1,000 resampled datasets to estimate the race-specific cases averted per 1,000 of anxiety if all racial groups had the same exposure distribution of ACEs as Whites. Simulated cases averted were greatest for the Multiracial group, (median = -4.17 cases per 1,000, 95% CI: -7.42, -1.86). The model also predicted smaller risk reductions for Black participants (-0.76, 95% CI: -1.53, -0.19). CIs around estimates for other racial groups included the null. An intervention to reduce racial disparities in exposure to ACEs could help reduce the inequitable burden of anxiety on the Multiracial population. Stochastic methods support consequentialist approaches to racial health equity, and can encourage greater dialogue between public health researchers, policymakers, and practitioners.

Childhood adversity and time-to-pregnancy in a preconception cohort.

We examined the association between childhood adversity and fecundability (the per-cycle probability of conception), and the extent to which childhood social support modified this association. We used data from 6,318 female participants aged 21-45 years in Pregnancy Study Online (PRESTO), a North American prospective preconception cohort study (2013-2022). Participants completed a baseline questionnaire, bimonthly follow-up questionnaires (until pregnancy or a censoring event), and a supplemental questionnaire on experiences across the life course including adverse childhood experiences (ACE) and social support (using the modified Berkman-Syme Social Network Index [SNI]). We used proportional probabilities regression models to compute fecundability ratios (FR) and 95% confidence intervals (CI), adjusting for potential confounders and precision variables. Adjusted FRs for ACE scores 1-3 and ≥4 vs. 0 were 0.91 (95% CI: 0.85, 0.97) and 0.84 (95% CI: 0.77, 0.91), respectively. FRs for ACE scores ≥4 vs. 0 were 0.86 (95% CI: 0.78, 0.94) among participants reporting high childhood social support (SNI ≥4) and 0.78 (95% CI: 0.56, 1.07) among participants reporting low childhood social support (SNI <4). Our findings confirm results from two previous studies and indicate that high childhood social support slightly buffered the effects of childhood adversity on fecundability.

DNA methylation as a possible causal mechanism linking childhood adversity and health: Results from two-sample mendelian randomization study.

Childhood adversity is an important risk factor for adverse health across the life course. Epigenetic modifications, such as DNA methylation (DNAm), are one hypothesized mechanism linking adversity to disease susceptibility. Yet, few studies have determined whether adversity-related DNAm alterations are causally related to future health outcomes or if their developmental timing plays a role in these relationships. Here, we used two-sample Mendelian Randomization to obtain stronger causal inferences about the association between adversity-associated DNAm loci across development (i.e., birth; childhood; adolescence; young adulthood) and 24 mental, physical, and behavioral health outcomes. We identified particularly strong associations between adversity-associated DNAm and ADHD, depression, obsessive-compulsive disorder, suicide attempts, asthma, coronary artery disease, and chronic kidney disease. A greater number of associations were identified for birth and childhood DNAm, while adolescent and young adulthood DNAm were more closely linked to mental health. Childhood DNAm loci also showed primarily risk suppressing relationships with health outcomes, suggesting that DNAm might reflect compensatory or buffering mechanisms against childhood adversity, rather than acting solely as an indicator of disease risk. Together, our results suggest adversity-related DNAm alterations are linked to both physical and mental health outcomes, with particularly strong impacts of DNAm differences emerging earlier in development.

A future food boom rescues the negative effects of early-life adversity on adult lifespan in a small mammal.

Early-life adversity, even when transient, can have lasting effects on individual phenotypes and reduce lifespan across species. If these effects can be mitigated by a high-quality later-life environment, then differences in future resources may explain variable resilience to early-life adversity. Using data from over 1000 wild North American red squirrels, we tested the hypothesis that the costs of early-life adversity for adult lifespan could be offset by later-life food abundance. We identified six adversities that reduced juvenile survival in the first year of life, though only one-birth date-had continued independent effects on adult lifespan. We then built a weighted early-life adversity (wELA) index integrating the sum of adversities and their effect sizes. Greater weighted early-life adversity predicted shorter adult lifespans in males and females, but a naturally occurring food boom in the second year of life ameliorated this effect. Experimental food supplementation did not replicate this pattern, despite increasing lifespan, indicating that the buffering effect of a future food boom may hinge on more than an increase in available calories. Our results suggest a non-deterministic role of early-life conditions for later-life phenotype, highlighting the importance of evaluating the consequences of early-life adversity in the context of an animal's entire life course.

Childhood trauma moderates schizotypy-related brain morphology: analyses of 1182 healthy individuals from the ENIGMA schizotypy working group.

BACKGROUND: Schizotypy represents an index of psychosis-proneness in the general population, often associated with childhood trauma exposure. Both schizotypy and childhood trauma are linked to structural brain alterations, and it is possible that trauma exposure moderates the extent of brain morphological differences associated with schizotypy. METHODS: We addressed this question using data from a total of 1182 healthy adults (age range: 18-65 years old, 647 females/535 males), pooled from nine sites worldwide, contributing to the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Schizotypy working group. All participants completed both the Schizotypal Personality Questionnaire Brief version (SPQ-B), and the Childhood Trauma Questionnaire (CTQ), and underwent a 3D T1-weighted brain MRI scan from which regional indices of subcortical gray matter volume and cortical thickness were determined. RESULTS: A series of multiple linear regressions revealed that differences in cortical thickness in four regions-of-interest were significantly associated with interactions between schizotypy and trauma; subsequent moderation analyses indicated that increasing levels of schizotypy were associated with thicker left caudal anterior cingulate gyrus, right middle temporal gyrus and insula, and thinner left caudal middle frontal gyrus, in people exposed to higher (but not low or average) levels of childhood trauma. This was found in the context of morphological changes directly associated with increasing levels of schizotypy or increasing levels of childhood trauma exposure. CONCLUSIONS: These results suggest that alterations in brain regions critical for higher cognitive and integrative processes that are associated with schizotypy may be enhanced in individuals exposed to high levels of trauma.

Youth adversity and trajectories of depression/anxiety symptoms in adolescence in the context of intersectionality in the United Kingdom.

BACKGROUND: Youth adversity is associated with persistence of depression and anxiety symptoms. This association may be greater for disadvantaged societal groups (such as females) compared with advantaged groups (e.g. males). Given that persistent symptoms are observed across a range of disadvantaged, minoritized, and neurodivergent groups (e.g. low compared with high socio-economic status [SES]), the intersection of individual characteristics may be an important moderator of inequality. METHODS: Data from HeadStart Cornwall (N = 4441) was used to assess the effect of youth adversity on combined symptoms of depression and anxiety (Strengths and Difficulties Questionnaire emotional problems subscale) measured at three time-points in 11-14-year-olds. Latent trajectories and regressions were estimated for eight intersectionality profiles (based on gender, SES, and hyperactivity/inattention), and moderating effects of the individual characteristics and their intersections were estimated. RESULTS: Youth adversity was associated with higher average depression/anxiety symptoms at baseline (11-12-years) across all intersectionality profiles. The magnitude of effects differed across profiles, with suggestive evidence for a moderating effect of youth adversity on change over time in depression/anxiety symptoms attributable to the intersection between (i) gender and SES; and (ii) gender, SES, and hyperactivity/inattention. CONCLUSIONS: The detrimental effects of youth adversity pervade across intersectionality profiles. The extent to which these effects are moderated by intersectionality is discussed in terms of operational factors. The current results provide a platform for further research, which is needed to determine the importance of intersectionality as a moderator of youth adversity on the development of depression and anxiety symptoms in adolescence.

Environmental risk factors for schizophrenia and bipolar disorder from childhood to diagnosis: a Swedish nested case-control study.

BACKGROUND: Shared genetic risk between schizophrenia (SCZ) and bipolar disorder (BD) is well-established, yet the extent to which they share environmental risk factors remains unclear. We compare the associations between environmental exposures during childhood/prior to disorder onset with the risk of developing SCZ and BD. METHODS: We conducted a Swedish register-based nested case-control study using 4184 SCZ cases and 18 681 BD cases diagnosed 1988-2013. Cases were matched to five controls by birth year, birth region, and sex. Conditional logistic regression was used to estimate incidence rate ratios (IRR) for SCZ and BD for each exposure (severe childhood infections, adverse childhood experiences (ACEs), substance use disorders (SUDs), urban birth/longest residence). RESULTS: All SUD types were associated with very high risk (IRR 4.9-25.5), and all forms of ACEs with higher risk (IRR 1.5-4.3) for both disorders. In the mutually adjusted models, ACEs demonstrated slightly higher risk for BD (SCZ IRR 1.30, 1.19-1.42; BD IRR 1.49, 1.44-1.55), while for SUD, risk was higher for SCZ (SCZ IRR 9.43, 8.15-10.92; BD IRR 5.50, 5.15-5.88). Infections were associated with increased risk of BD (IRR 1.21, 1.17-1.26) but not SCZ. Urban birth and urban longest residence were associated with higher risk of SCZ (IRR 1.19, 1.03-1.37), while only the combination of urban birth and rural longest residence showed higher risk for BD (IRR 1.24, 1.13-1.35). CONCLUSIONS: There were both shared and unique environmental risk factors: SUDs and ACEs were risk factors for both disorders, while infections were more strongly associated with BD and urbanicity with SCZ.

Effects of inflammation, childhood adversity, and psychiatric symptoms on brain morphometrical phenotypes in bipolar II depression.

BACKGROUND: The neuroanatomical alteration in bipolar II depression (BDII-D) and its associations with inflammation, childhood adversity, and psychiatric symptoms are currently unclear. We hypothesize that neuroanatomical deficits will be related to higher inflammation, greater childhood adversity, and worse psychiatric symptoms in BDII-D. METHODS: Voxel- and surface-based morphometry was performed using the CAT toolbox in 150 BDII-D patients and 155 healthy controls (HCs). Partial Pearson correlations followed by multiple comparison correction was used to indicate significant relationships between neuroanatomy and inflammation, childhood adversity, and psychiatric symptoms. RESULTS: Compared with HCs, the BDII-D group demonstrated significantly smaller gray matter volumes (GMVs) in frontostriatal and fronto-cerebellar area, insula, rectus, and temporal gyrus, while significantly thinner cortices were found in frontal and temporal areas. In BDII-D, smaller GMV in the right middle frontal gyrus (MFG) was correlated with greater sexual abuse (r = -0.348, q < 0.001) while larger GMV in the right orbital MFG was correlated with greater physical neglect (r = 0.254, q = 0.03). Higher WBC count (r = -0.227, q = 0.015) and IL-6 levels (r = -0.266, q = 0.015) was associated with smaller GMVs in fronto-cerebellar area in BDII-D. Greater positive symptoms was correlated with larger GMVs of the left middle temporal pole (r = 0.245, q = 0.03). CONCLUSIONS: Neuroanatomical alterations in frontostriatal and fronto-cerebellar area, insula, rectus, temporal gyrus volumes, and frontal-temporal thickness may reflect a core pathophysiological mechanism of BDII-D, which are related to inflammation, trauma, and psychiatric symptoms in BDII-D.

The association of adverse childhood experiences with long-term outcomes of psychosis: a 21-year prospective cohort study after a first episode of psychosis.

BACKGROUND: Evidence suggests a possible relationship between exposure to childhood adversity (CA) and functional impairment in psychosis. However, the impact of CA on long-term outcomes of psychotic disorders remains poorly understood. METHODS: Two hundred and forty-three patients were assessed at their first episode of psychosis for CA and re-assessed after a mean of 21 years of follow-up for several outcome domains, including symptoms, functioning, quality of life, cognitive performance, neurological dysfunction, and comorbidity. The unique predictive ability of CA exposure for outcomes was examined using linear regression analysis controlling for relevant confounders, including socioeconomic status, family risk of schizophrenia, and obstetric complications. RESULTS: There were 54% of the patients with a documented history of CA at mild or higher levels. CA experiences were more prevalent and severe in schizophrenia than in other psychotic disorders (p < 0.001). Large to very large effect sizes were observed for CA predicting most role functioning variables and negative symptoms (ΔR2 between 0.105 and 0.181). Moderate effect sizes were observed for positive symptoms, personal functioning, impaired social cognition, impaired immediate verbal learning, poor global cognition, internalized stigma, poor personal recovery, and drug abuse severity (ΔR2 between 0.040 and 0.066). A dose-response relationship was observed between levels of CA and severity of outcome domains. CONCLUSION: Our results suggest a strong and widespread link between early adversity exposure and outcomes of psychotic disorders. Awareness of the serious long-term consequences of CA should encourage better identification of those at risk and the development of effective interventions.

Early life adversity is associated with differential gene expression in immune cells: A cluster-based analysis across an acute psychosocial stressor.

Elucidating mechanisms by which early-life adversity (ELA) contributes to increased disease risk is important for mitigating adverse health outcomes. Prior work has found differences in immune cell gene expression related to inflammation and mitochondrial activity. Using a within-person between-group experimental design, we investigated differences in gene expression clusters across acute psychosocial stress and no-stress conditions. Participants were young adults (N = 29, aged 18 - 25 years, 62 % female, 47 % with a history of ELA). Gene expression was assessed in peripheral blood mononuclear cells collected at 8 blood draws spanning two 5-hour sessions (stress vs. no-stress) separated by a week, 4 across each session (number of observations = 221). We applied two unsupervised gene clustering methods - latent profile analysis (LPA) and weighted gene co-expression analysis (WGCNA) - to cluster genes with similar expression patterns across participants. LPA identified 11 clusters, 7 of which were significantly associated with ELA-status. WGCNA identified 5 clusters, 3 of which were significantly associated with ELA-status. LPA- and WGCNA-identified clusters were correlated, and all clusters were highly preserved across sessions and time. There was no significant effect of acute stress on cluster gene expression, but there was a significant effect of time, and significant differences by ELA-status. ELA-associated clusters related to RNA splicing/processing, inflammation, leukocyte differentiation and division, and mitochondrial activity were differentially expressed across time: ELA-exposed individuals showed decreased expression of these clusters at 90-minutes while controls showed increased expression. Our findings replicate previous work in this area and highlight additional mechanisms by which ELA may contribute to disease risk.

Stress-related gene regulation: Do isolated and connected individuals differ?

BACKGROUND: Social isolation and loneliness (known as social disconnection, collectively) lead to serious downstream health effects, including shortening of lifespan and higher risk for cardiac disease. We must better understand how isolation and loneliness lead to these negative health outcomes. Previous literature has demonstrated that social motivation and social ability are contributors to the likelihood of social isolation and loneliness. We examined the effect of the above social factors on immune gene expression in socially-connected and -isolated individuals. METHODS: Recruitment occurred via two online advertisements, one for socially isolated individuals and another for general research participants. Participants (n = 102) were separated into groups (isolated versus connected) based on which ad they responded to, and provided data on isolation, loneliness, social motivation, and social ability. The Conserved Transcriptional Response to Adversity (CTRA) stress gene regulation program was assessed with genome-wide transcriptional profiling. RESULTS: CTRA gene expression patterns were reversed between connected and isolated groups across several variables. Social isolation was associated with higher CTRA levels in the connected group, but lower levels in the isolated group. Social approach was associated with lower CTRA levels in the connected group, but higher in the isolated group, and the converse was true for social avoidance. CTRA levels were minimally affected by social ability measures. CONCLUSION: Prior work on social isolation and loneliness has focused on loneliness and has identified many negative downstream health effects. In this study we demonstrate that objective social isolation may not be associated with the same negative downstream health effects, and in fact, social interaction may be more stressful than social isolation for some socially-isolated individuals.