Early life stress sensitizes youth to the influence of stress-induced cortisol on memory for affective words

Pitfalls and potential: Translating the two-hit model of early life stress from pre-clinical non-human experiments to human samples

Exposure to early life stress (ELS) has been linked to at least double the risk of psychopathology as well as higher morbidity and earlier mortality across the lifespan. For this reason, the field of developmental psychopathology has spent decades identifying factors that explain which individuals are at risk for negative health outcomes. Preclinical experiments in this field commonly test the "two-hit hypothesis", which explores how ELS potentiates vulnerability to pathogenic physiological and behavioral outcomes when an individual is exposed to a stressor later in development. Yet, translation of the two-hit hypothesis to humans is conceptually and practically challenging, thus impeding progress in the field. This review summarizes the two-hit hypothesis used in preclinical experiments as it pertains to two putative pathways linking ELS to psychopathology: the innate immune and neuroendocrine systems. This review also identifies important considerations when translating this model to humans and provides several recommendations. Specifically, attention to the "biological salience" of different forms of ELA and the concordance of that salience with later probes of the system are needed. Further, the consequences of ELS may be context-specific rather than ubiquitous, at least among young people. Within this conceptualization, "second hits" may be best operationalized using standardized acute challenges to the innate immune and neuroendocrine systems (e.g., psychosocial stress). Third, more explicit reporting of sex differences in the human literature is needed. Finally, preclinical experimental designs that more accurately reflect the natural occurrence of ELS in community samples will more effectively advance the understanding of developmental mechanisms that occur as a consequence of ELS.

Early life stress lastingly alters the function and AMPA-receptor composition of glutamatergic synapses in the hippocampus of male mice

Early postnatal life is a sensitive period of development that shapes brain structure and function later in life. Exposure to stress during this critical time window can alter brain development and may enhance the susceptibility to psychopathology and neurodegenerative disorders later in life. The developmental effects of early life stress (ELS) on synaptic function are not fully understood, but could provide mechanistic insights into how ELS modifies later brain function and disease risk. We here assessed the effects of ELS on synaptic function and composition in the hippocampus of male mice. Mice were subjected to ELS by housing dams and pups with limited bedding and nesting material from postnatal days (P) 2-9. Synaptic strength was measured in terms of miniature excitatory postsynaptic currents (mEPSCs) in the hippocampal dentate gyrus at three different developmental stages: the early postnatal phase (P9), preadolescence (P21, at weaning) and adulthood at 3 months of age (3MO). Hippocampal synaptosome fractions were isolated from P9 and 3MO tissue and analyzed for protein content to assess postsynaptic composition. Finally, dendritic spine density was assessed in the DG at 3MO. At P9, ELS increased mEPSC frequency and amplitude. In parallel, synaptic composition was altered as PSD-95, GluA3 and GluN2B content were significantly decreased. The increased mEPSC frequency was sustained up to 3MO, at which age, GluA3 content was significantly increased. No differences were found in dendritic spine density. These findings highlight how ELS affects the development of hippocampal synapses, which could provide valuable insight into mechanisms how ELS alters brain function later in life.

The Influence of COVID-19 in Endocrine Research: Critical Overview, Methodological Implications and a Guideline for Future Designs

The COVID-19 pandemic has changed many aspects of people's lives, including not only individual social behavior, healthcare procedures, and altered physiological and pathophysiological responses. As a result, some medical studies may be influenced by one or more hidden factors brought about by the COVID-19 pandemic. Using the literature review method, we are briefly discussing the studies that are confounded by COVID-19 and facemask-induced partiality and how these factors can be further complicated with other confounding variables. Facemask wearing has been reported to produce partiality in studies of ophthalmology (particularly dry eye and related ocular diseases), sleep studies, cognitive studies (such as emotion-recognition accuracy research, etc.), and gender-influenced studies, to mention a few. There is a possibility that some other COVID-19 related influences remain unrecognized in medical research. To account for heterogeneity, current and future studies need to consider the severity of the initial illness (such as diabetes, other endocrine disorders), and COVID-19 infection, the timing of analysis, or the presence of a control group. Face mask-induced influences may confound the results of diabetes studies in many ways.

The role of early life adversity and inflammation in stress-induced change in reward and risk processes among adolescents

BACKGROUND

Early life adversity (ELA) has long been associated with increased risk for stress-related psychopathology, particularly depression. The neuroimmune network hypothesis posits that ELA increases sensitivity to psychosocial stress, moderating the association between increases in peripheral markers of inflammation and decreases in reward outcomes linked to anhedonia and risk-taking behaviors. The present study examined this hypothesis in a sample of adolescents by using acute psychosocial stress to probe the role of inflammatory signaling in behavioral measures of reward and risk processing.

METHOD

80 adolescents [13.86 years (SD = 1.54); 45 % female], oversampled for ELA, underwent the Trier Social Stress Test for Children while providing blood samples immediately before and 60-minutes after stress onset. Blood samples were assayed for plasma IL-6. One hour before stress onset, and then 60 min after, participants completed computer-administered behavioral tasks measuring reward (Pirate Task) and risk (Balloon Analog Risk Task).

RESULTS

ELA moderated the association between increases in IL-6 and decreases in risk tolerance in pursuit of rewards (p = 0.003) and reward response bias (p = 0.04). Stress-induced increases in IL-6 were associated with decreases in pumps for rewards among adolescents exposed to high, relative to little or no, ELA. Further, greater IL-6 increases were associated with increases in bias toward high relative to low value rewards among adolescents with low adversity exposure but not among those exposed to higher adversity.

CONCLUSIONS

The present study provides the first evidence in a pediatric sample that ELA may alter the role of stress-induced inflammation in reward and risk processing, and may extend our understanding of why stress leads to depression in this high-risk population.

Childhood maltreatment and within-person associations between cortisol and affective experience

Glucocorticoids exert profound effects on the brain and behavior, but cortisol concentrations are rarely linked to subjectively reported emotional states in humans. This study examined whether the link between cortisol and subjective anxiety varied by childhood maltreatment history. To do this, 97 individuals (60.8% female) participated in a standardized stress task in the laboratory (Trier Social Stress Test, TSST) while providing serial ratings of their feelings of anxiety as well as cortisol samples in blood. These measurements were collected nine times across the laboratory visit, from immediately before the TSST to 65 minutes after stress initiation. We estimated the within-person association between cortisol concentrations and momentary feelings of anxiety for individuals with and without exposure to childhood maltreatment, measured via self-report on the Childhood Trauma Questionnaire (CTQ). Individuals exposed to maltreatment during childhood reported the greatest feelings of anxiety when cortisol concentrations were lowest. This pattern was exaggerated among female participants, those with posttraumatic stress disorder (PTSD), and those exposed to emotional neglect relative to other forms of maltreatment. Early life adversity, such as parental maltreatment, may alter the role of cortisol in affective experiences. This observation may provide preliminary, translational evidence of a novel pathway through which stress may lead to and maintain internalizing symptoms in humans. More studies accounting for the moderating role of childhood maltreatment in biobehavioral pathways are needed.