Introduction The COVID-19 (coronavirus disease 2019)-related pandemic represents a global source of societal and health burden. Yet, the impact of the pandemic on people with severe mental illness, including bipolar disorder (BD), remains unclear, warranting scoping review on the matter. Methods The MEDLINE and EMBASE databases were systematically searched from inception up to April 24, 2021, adopting broad inclusion criteria to assess a variety of clinical and public health themes related to people with a primary diagnosis of BD during the COVID-19 pandemics. The present work complying with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) registered in the Open Science Framework (OSF) repository ( https://osf.io/7evpx/ ). Results Fourteen papers informed the present scoping review. Four major themes were identified: i) impact of COVID-19-related stressors on BD; ii) impact of COVID-19 on mental health service utilization among people with BD; iii) impact of BD on the risk of acquiring SARS-CoV-2 infection; iv) engagement in preventative behaviors among people with BD. Additional themes warranting further research were nonetheless detected. Limitations Further original studies are needed. Conclusion The present study confirmed the high-vulnerability hypothesis concerning people with BD versus the general population, reinforcing the need for further research related to the COVID-19 pandemic. Additional information is warranted to compare the impact of the pandemic period among BD people against pre-pandemic records, the general population, and other severe mental illnesses, namely people with schizophrenia or major depressive disorder, to inform the public health and the delivery of patient-tailored interventions.

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Few longitudinal studies have so far investigated the impact of sustained COVID‐19 among people with pre‐existing psychiatric disorders. We conducted a prospective study involving people with serious mental illness ( n = 114) and healthy controls ( n = 41) to assess changes in the Perceived Stress Scale, Generalized Anxiety Disorder Scale, Patient Health Questionnaire, and Specific Psychotic Experiences Questionnaire scores 18 months after the COVID‐19 pandemic outset. Subjects underwent interviews with a mental health professional in April 2020 and at the end of the local third wave (October 2021). A significant increase in perceived stress was found in healthy controls, especially females. Psychiatric patients showed a significant worsening of anxiety symptoms compared to baseline records ( t = −2.3, p = 0.036). Patients who rejected vaccination had significantly higher paranoia scores compared to those willing to get vaccinated ( U = 649.5, z = −2.02, p = 0.04). These findings indicate that COVID‐19's sustained emergency may cause enduring consequences on mental health, soliciting further investigations.

Background Homelessness has been associated with multiple detrimental health outcomes across observational studies. However, relatively few randomized controlled trials (RCTs) have been conducted on people who experience homelessness (PEH). Thus, this umbrella review ranked the credibility of evidence derived from systematic reviews (SRs) and meta-analyses (MAs) of observational studies investigating the associations between homelessness and any health outcome as well as RCTs targeting health needs in this population. Methods Several databases were systematically searched from inception through April 28, 2021. Any SR and/or MA reporting quantitative data and providing a control group were eligible for inclusion. The credibility of the evidence derived from observational studies was appraised by considering the significance level of the association and the largest study, the degree of heterogeneity, the presence of small-study effects as well as excess significance bias. The credibility of evidence was then ranked in five classes. For SRs and/or MAs of RCTs, we considered the level of significance and whether the prediction interval crossed the null. The AMSTAR-2 and AMSTAR-plus instruments were adopted to further assess the methodological quality of SRs and/or MAs. The Newcastle-Ottawa Scale (NOS) was employed to further appraise the methodological quality of prospective cohort studies only; a sensitivity analysis limited to higher quality studies was conducted. Results Out of 1549 references, 8 MAs and 2 SRs were included. Among those considering observational studies, 23 unique associations were appraised. Twelve of them were statistically significant at the p≤0.005 level. Included cases had worst health-related outcomes than controls, but only two associations reached a priori-defined criteria for convincing (class I) evidence namely hospitalization due to any cause among PEH diagnosed with HIV infection, and the occurrence of falls within the past year among PEH. According to the AMSTAR-2 instrument, the methodological quality of all included SRs and/or MAs was “critically low.” Interventional studies were scant. Conclusion While homelessness has been repeatedly associated with detrimental health outcomes, only two associations met the criteria for convincing evidence. Furthermore, few RCTs were appraised by SRs and/or MAs. Our umbrella review also highlights the need to standardize definitions of homelessness to be incorporated by forthcoming studies to improve the external validity of the findings in this vulnerable population.

Impairment of insulin action and metabolic dysregulation have traditionally been associated with schizophrenia, although the molecular basis of such association remains still elusive. The present meta-analysis aims to assess the impact of insulin action manipulations (i.e., hyperinsulinemia, hypoinsulinemia, systemic or brain insulin resistance) on glutamatergic, dopaminergic, γ-aminobutyric acid (GABA)ergic, and serotonergic pathways in the central nervous system. More than one hundred outcomes, including transcript or protein levels, kinetic parameters, and other components of the neurotransmitter pathways, were collected from cultured cells, animals, or humans, and meta-analyzed by applying a random-effects model and adopting Hedges’g to compare means. Two hundred fifteen studies met the inclusion criteria, of which 180 entered the quantitative synthesis. Significant impairments in key regulators of synaptic plasticity processes were detected as the result of insulin handlings. Specifically, protein levels of N-methyl-D-aspartate receptor (NMDAR) subunits including type 2A (NR2A) (Hedges’ g = −0.95, 95%C.I. = −1.50, −0.39; p = 0.001; I2 = 47.46%) and 2B (NR2B) (Hedges’g = −0.69, 95%C.I. = −1.35, −0.02; p = 0.043; I2 = 62.09%), and Postsynaptic density protein 95 (PSD-95) (Hedges’g = −0.91, 95%C.I. = −1.51, −0.32; p = 0.003; I2 = 77.81%) were found reduced in insulin-resistant animal models. Moreover, insulin-resistant animals showed significantly impaired dopamine transporter activity, whereas the dopamine D2 receptor mRNA expression (Hedges’g = 3.259; 95%C.I. = 0.497, 6.020; p = 0.021; I2 = 90.61%) increased under insulin deficiency conditions. Insulin action modulated glutamate and GABA release, as well as several enzymes involved in GABA and serotonin synthesis. These results suggest that brain neurotransmitter systems are susceptible to insulin signaling abnormalities, resembling the discrete psychotic disorders’ neurobiology and possibly contributing to the development of neurobiological hallmarks of treatment-resistant schizophrenia.