Interactions Between Experience, Genotype and Sex in the Development of Individual Coping Strategies

How can sleep disorders affect our reaction towards external stressors: a lesson from the COVID-19 outbreak

BACKGROUND

The COVID-19 outbreak produced extensive psychological consequences, especially among vulnerable populations. Sleep was identified as one of the most common "indirect targets" of the pandemia, with up to 74.8% of patients surviving from COVID-19 complaining of new-onset sleep disorders. However, so far, the clinic-psychological impact of the outbreak in patients affected by pre-existing sleep disorders has not been examined in details.

MATERIALS AND METHODS

In the present study, we aim to assess the effect of the COVID-19 outbreak in a cohort of 190 adult patients affected by sleep disorders, compared to 265 age and sex-matched healthy sleepers. The assessment was implemented throughout the use of ad hoc anamnestic questions, exploration of dream content, and validated questionnaires, aiming to capture the broad range of the neuropsychological nuances of the COVID-19 impact.

RESULTS

Subjects with pre-existent sleep disorders faced a more severe impact in terms of sleep quality and amount compared to healthy sleepers, presenting longer sleep latency, reduced sleep efficacy, and greater use of hypnotics and medications. On the other hand, healthy sleepers experienced deeper variation in sleeping habits, sleep duration, and greater impact on dream activity in terms of content, emotionality, and presence of recurrent dreams. Finally, in our sample, being female represents an important aggravating factor in the pandemic experience, both in terms of sleep deterioration and with respect to physical and mental health. For instance, females indeed presented the highest scores of Pittsburgh Sleep Quality Index (PSQI) both in cases and control groups (respectively 10 ± 3.8 vs 7.3 ± 3.9 in cases and 6.6 ± 3.6 vs 6.0 ± 3.4 in controls, p-value < 0.001).

CONCLUSION

Pre-existent sleep disorders and the female sex might represent risk factors increasing the clinic-psychological burden in dramatic scenarios, such as the COVID-19 pandemia, requiring dedicated attention from clinicians.

The cortisol switch between vulnerability and resilience

In concert with neuropeptides and transmitters, the end products of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone (CORT), promote resilience: i.e., the ability to cope with threats, adversity, and trauma. To exert this protective action, CORT activates mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) that operate in a complementary manner -as an on/off switch- to coordinate circadian events, stress-coping, and adaptation. The evolutionary older limbic MR facilitates contextual memory retrieval and supports an on-switch in the selection of stress-coping styles at a low cost. The rise in circulating CORT concentration after stress subsequently activates a GR-mediated off-switch underlying recovery of homeostasis by providing the energy for restraining the primary stress reactions and promoting cognitive control over emotional reactivity. GR activation facilitates contextual memory storage of the experience to enable future stress-coping. Such complementary MR-GR-mediated actions involve rapid non-genomic and slower gene-mediated mechanisms; they are time-dependent, conditional, and sexually dimorphic, and depend on genetic background and prior experience. If coping fails, GR activation impairs cognitive control and promotes emotional arousal which eventually may compromise resilience. Such breakdown of resilience involves a transition to a chronic stress construct, where information processing is crashed; it leads to an imbalanced MR-GR switch and hence increased vulnerability. Novel MR-GR modulators are becoming available that may reset a dysregulated stress response system to reinstate the cognitive flexibility required for resilience.

A mouse model of the 3-hit effects of stress: Genotype controls the effects of life adversities in females

Helplessness is a dysfunctional coping response to stressors associated with different psychiatric conditions. The present study tested the hypothesis that early and adult adversities cumulate to produce helplessness depending on the genotype (3-hit hypothesis of psychopathology). To this aim, we evaluated whether Chronic Unpredictable Stress (CUS) differently affected coping and mesoaccumbens dopamine (DA) responses to stress challenge by adult mice of the C57BL/6J (B6) and DBA/2J (D2) inbred strains depending on early life experience (Repeated Cross Fostering, RCF). Three weeks of CUS increased the helplessness expressed in the Forced Swimming Test (FST) and the Tail Suspension Test by RCF-exposed female mice of the D2 strain. Moreover, female D2 mice with both RCF and CUS experiences showed inhibition of the stress-induced extracellular DA outflow in the Nucleus Accumbens, as measured by in vivo microdialysis, during and after FST. RCF-exposed B6 mice, instead, showed reduced helplessness and increased mesoaccumbens DA release. The present results support genotype-dependent additive effects of early experiences and adult adversities on behavioral and neural responses to stress by female mice. To our knowledge, this is the first report of a 3-hit effect in an animal model. Finally, the comparative analyses of behavioral and neural phenotypes expressed by B6 and D2 mice suggest some translationally relevant hypotheses of genetic risk factors for psychiatric disorders.

Role of Stress-Related Dopamine Transmission in Building and Maintaining a Protective Cognitive Reserve

This short review presents the hypothesis that stress-dependent dopamine (DA) transmission contributes to developing and maintaining the brain network supporting a cognitive reserve. Research has shown that people with a greater cognitive reserve are better able to avoid symptoms of degenerative brain changes. The paper will review evidence that: (1) successful adaptation to stressors involves development and stabilization of effective but flexible coping strategies; (2) this process requires dynamic reorganization of functional networks in the adult brain; (3) DA transmission is amongst the principal mediators of this process; (4) age- and disease-dependent cognitive impairment is associated with dysfunctional connectivity both between and within these same networks as well as with reduced DA transmission.