Psychological and cognitive impact of stress: examining economic stressors and mnemonic discrimination as predictors of PTSD and cognitive decline

This dissertation explores the profound impact of traumatic and stressful events, such as the COVID-19 pandemic, on mental health and cognitive functions, with a specific focus on the Italian population in the post-pandemic context. Economic downturns, such as the one that followed the pandemic, have widespread effects on public health and well-being, leading to significant mental health challenges tied to socioeconomic stressors like job insecurity, financial strain, and unemployment (Wang & Fattore, 2020). During economic downturns people lose their jobs, increasing the likelihood that they will struggle to afford basic necessities, pay bills, or handle unexpected expenses. All these conditions induce psychological distress and increase the prevalence of mental health disorders, dysfunctional behaviors, and even suicide rates (Frasquilho et al., 2016). Financial stressors are particularly damaging because they are ongoing, and their psychological effects may extend well beyond the acute phase of a crisis. As Lanz et al. (2023) noted, persistent financial stress has a lasting impact on mental health, continuing to drive psychological distress over time. Chronic stress and trauma can lead to neurobiological changes, particularly in systems that regulate stress responses, such as the hypothalamic-pituitary-adrenal (HPA) axis. According to Sherin and Nemeroff (2011), these changes often affect the structural and functional integrity of the hippocampus, a brain region critical for memory and learning, which is especially susceptible to stress-induced damages. These alterations have been linked not only to stress-related disorders, such as PTSD but also to neurodegenerative diseases like Alzheimer’s Disease (AD; Greenberg et al., 2014). Also, past research highlighted that there is an association between these disorders, as individuals with PTSD face more than double the risk of being diagnosed with dementia compared to those without PTSD (Günak et al., 2020). According to the World Health Organization, AD currently ranks as the seventh leading cause of death worldwide and is a major contributor to disability and dependency in older adults. In addition, individuals’ socioeconomic condition may be a risk factor for the development of dementia: in fact, approximately 60% of AD cases occur in low- and middle-income countries (WHO, 2023). Each year, nearly 10 million new dementia cases are 3 diagnosed, thus it is crucial to find interventions that could slow symptoms progression and ease the burden on healthcare systems (Belliart-Guérin & Planche, 2023). Understanding how stress affects cognitive functions, particularly mnemonic discrimination, is essential for uncovering potential early warning signs of mental health issues and cognitive decline. Mnemonic discrimination refers to the ability to distinguish between similar but distinct memories, a skill crucial for everyday cognitive functions (Stark et al., 2013). When this ability is compromised, it can contribute to increased generalization, where similar but not identical experiences are mistakenly associates (Lange et al., 2017). The Mnemonic Similarity Task (MST) has emerged as a promising tool for assessing this specific cognitive function, as is highly sensitive to hippocampal function (Stark et al., 2013). As demonstrated in numerous studies, MST can identify deficits in mnemonic discrimination that may serve as early indicators, or prodromal signs, of disorders associated with hippocampal alterations, like Post- Traumatic Stress Disorder (PTSD) and forms of cognitive decline, such as those seen in the early stages of dementia (Lange et al., 2017; Vandelip et al., 2024). By detecting these deficits early, MST offers a valuable means of anticipating conditions before they fully develop, allowing for timely interventions. Early detection of mnemonic discrimination deficits opens up important opportunities for targeted prevention strategies. Such strategies could include both therapeutic and policy-driven interventions aimed at preserving cognitive functions and mitigating the adverse effects of prolonged stress, such as economic stress, and trauma on mental health. Preventative measures and timely support can not only improve individual well-being but also reduce the societal and economic burdens associated with mental health conditions. The present study, we aim to contribute to the growing body of research on the role of mnemonic discrimination in mental health and cognitive functions. Our goal is to further validate the MST as a diagnostic tool and to emphasize the importance of early interventions, ultimately fostering a better understanding of how stress-related cognitive changes can be identified and addressed in a preventative context. The present work is organized into three distinct studies. 4 The first study, titled "Cross-Sectional Study of Economic Stressors in the Post- Pandemic Era: Insights from the Italian Population", investigates how economic stressors, such as financial hardship and perceived job insecurity, contribute to the development of PTSD-related outcomes. Despite experiencing multiple economic downturns in recent years, limited research exists in the Italian context examining the post-pandemic implications of these stressors on mental health. The present study contributes to fill this gap by analyzing data from an online questionnaire, revealing that financial hardship and perceived job insecurity significantly correlate with the intensity of PTSD-related manifestations referred. Moreover, perceived job insecurity was associated with employment and salary satisfaction, but not with professional growth satisfaction. The second study, titled "Exploring the Relationship Between Mnemonic Discrimination and PTSD-Related Symptoms in a General Population Sample", explores the cognitive repercussions of potentially traumatic events. Given that a significant portion of individuals experience a considerable number of potentially traumatic events, there is an elevated risk of developing PTSD, especially during crises like the COVID-19 pandemic (Yunitri et al., 2022). This study focuses on the cognitive ability to discriminate similar stimuli, known as mnemonic discrimination ability, which can contribute to fear overgeneralization symptoms in PTSD patients (Lange et al., 2017; Bernstein et al., 2020). Using the object version of the MST (Stark et al., 2013), the study found no significant correlation between mnemonic discrimination of neutral everyday objects and the intensity of PTSD-related symptoms, suggesting that PTSD-related mnemonic deficits may be more specific to emotional stimuli. The third study, titled "Mnemonic Discrimination in Cognitive Decline and NeuroCOVID", explores how mnemonic discrimination ability is affected across various neurological conditions. Mnemonic discrimination is a process heavily dependent on the dentate gyrus of the hippocampus (Yassa & Stark, 2011; Leal & Yassa, 2018). This study emphasizes how mnemonic discrimination deficits manifest in conditions such as Subjective Cognitive Decline (SCD), Mild Cognitive Impairment (MCI), Alzheimer’s Disease (AD), and long-term neurocognitive complications of COVID-19, often referred to as NeuroCOVID. Recent literature has highlighted that the persistent cognitive symptoms following COVID-19 may parallel those observed in AD, with similar 5 neuroinflammatory mechanisms (Nouraeinejad, 2023). The results demonstrated significant impairments in mnemonic discrimination among MCI and AD groups compared to control group. No significant differences in MST performance were observed between NeuroCOVID, SCD and control groups. However, the data collection is still underway, and the results presented should be considered preliminary. Given the increasing relevance of mental health in the face of ongoing global challenges, these studies provide critical insights into how socio-economic, psychological, and neurological factors interplay in shaping mental health outcomes. By focusing on these issues in the Italian post-pandemic context, this dissertation contributes to a growing body of literature aimed at understanding the long-term impact of both economic and health-related crises on cognitive and psychological well-being. In the following chapters, each study will be discussed in detail.