Stress Biomarkers in Young Adult University Students Before, During, and After the COVID-19 Pandemic: A Longitudinal...

Although life expectancy has increased, modern life has intensified stress factors, affecting both physiology and mental health. The COVID-19 pandemic has been a prolonged, stressful event with significant implications for young adults, especially students. The hypothalamic-pituitary-adrenal (HPA) axis and related hormonal markers such as cortisol and free cortisol are important biomarkers of the body's response to stress, while dopamine and serotonin are neurochemical biomarkers of mood and pleasure.

This study aims to assess and correlate hormonal stress biomarkers and neurotransmitters with behavioral factors over time, to investigate the effects of the pandemic on the neurobiology and behavior of young adult university students.

This is a prospective non-interventional cohort study that examines the levels of key stress hormones (cortisol, free cortisol), mood and pleasure neurotransmitters (serotonin, dopamine), as well as behavioral and demographic parameters (screen exposure, BMI, physical activity) in students from health faculties of various universities in northern Greece, aged 18-25 years, in three time periods: before (2019-2020), during (2020-2022), and after the pandemic (2023-2025). The biomarkers were measured in serum samples, using immunoenzymatic methods for dopamine and serotonin and immunochemiluminescence for cortisol and free cortisol.

The findings showed a significant increase in total and free cortisol levels and mobile phone use during and after the pandemic, as well as a sustained decrease in serotonin and dopamine. In contrast, regular physical exercise was associated with a more favorable hormonal profile, regardless of the epoch.

The findings highlight the impact of long-term stressors on the biochemical balance of stress-hormones and neurotransmitters and the long-term biological and behavioral effects of the pandemic on university students, with potential consequences for their future somatic and mental health. Physical exercise emerges as an important protective factor against the effects of chronic stress, as does timely mental health monitoring and support.