Background: The Coronavirus disease 2019 (COVID-19) pandemic is an unprecedented traumatic event influencing the healthcare, economic, and social welfare systems worldwide. In order to slow the infection rates, lockdown has been implemented almost everywhere. Italy, one of the countries most severely affected, entered the “lockdown” on March 8, 2020.Methods: The COvid Mental hEalth Trial (COMET) network includes 10 Italian university sites and the National Institute of Health. The whole study has three different phases. The first phase includes an online survey conducted between March and May 2020 in the Italian population. Recruitment took place through email invitation letters, social media, mailing lists of universities, national medical associations, and associations of stakeholders (e.g., associations of users/carers). In order to evaluate the impact of lockdown on depressive, anxiety and stress symptoms, multivariate linear regression models were performed, weighted for the propensity score.Results: The final sample consisted of 20,720 participants. Among them, 12.4% of respondents (N = 2,555) reported severe or extremely severe levels of depressive symptoms, 17.6% (N = 3,627) of anxiety symptoms and 41.6% (N = 8,619) reported to feel at least moderately stressed by the situation at the DASS-21.According to the multivariate regression models, the depressive, anxiety and stress symptoms significantly worsened from the week April 9–15 to the week April 30 to May 4 (p < 0.0001). Moreover, female respondents and people with pre-existing mental health problems were at higher risk of developing severe depression and anxiety symptoms (p < 0.0001).Conclusions: Although physical isolation and lockdown represent essential public health measures for containing the spread of the COVID-19 pandemic, they are a serious threat for mental health and well-being of the general population. As an integral part of COVID-19 response, mental health needs should be addressed.

Stress and glucocorticoid hormones regulate hippocampal neurogenesis, but the molecular mechanisms underlying their effects are unknown. We, therefore, investigated the molecular signaling pathways mediating the effects of cortisol on proliferation, neuronal differentiation, and astrogliogenesis, in an immortalized human hippocampal progenitor cell line. In addition, we examined the molecular signaling pathways activated in the hippocampus of prenatally stressed rats, characterized by persistently elevated glucocorticoid levels in adulthood. In human hippocampal progenitor cells, we found that low concentrations of cortisol (100 nM) increased proliferation (+16%), decreased neurogenesis into microtubule-associated protein 2 (MAP2)-positive neurons (−24%) and doublecortin (Dcx)-positive neuroblasts (−21%), and increased differentiation into S100β-positive astrocytes (+23%). These effects were dependent on the mineralocorticoid receptor (MR) as they were abolished by the MR antagonist, spironolactone, and mimicked by the MR-agonist, aldosterone. In contrast, high concentrations of cortisol (100 μM) decreased proliferation (−17%) and neuronal differentiation into MAP2-positive neurons (−22%) and into Dcx-positive neuroblasts (−27%), without regulating astrogliogenesis. These effects were dependent on the glucocorticoid receptor (GR), blocked by the GR antagonist RU486, and mimicked by the GR-agonist, dexamethasone. Gene expression microarray and pathway analysis showed that the low concentration of cortisol enhances Notch/Hes-signaling, the high concentration inhibits TGFβ-SMAD2/3-signaling, and both concentrations inhibit Hedgehog signaling. Mechanistically, we show that reduced Hedgehog signaling indeed critically contributes to the cortisol-induced reduction in neuronal differentiation. Accordingly, TGFβ-SMAD2/3 and Hedgehog signaling were also inhibited in the hippocampus of adult prenatally stressed rats with high glucocorticoid levels. In conclusion, our data demonstrate novel molecular signaling pathways that are regulated by glucocorticoids in vitro, in human hippocampal progenitor cells, and by stress in vivo, in the rat hippocampus.