This article examines the role of the stress hormone Cortisol in modulating brain structure and function within the context of stress and the nervous system. Cortisol, produced via activation of the Hypothalamic–Pituitary–Adrenal axis (HPA) in response to stress, exerts a range of acute and chronic effects on neural circuits, cognitive processes, and emotional regulation. In the short term, cortisol may support adaptive responses to stress by enhancing alertness and memory consolidation; however, persistent elevation of cortisol levels is associated with structural brain changes, particularly in key regions such as the Hippocampus, Prefrontal cortex (PFC) and Amygdala, and with impaired cognitive function, mood disorders and increased risk of neurodegenerative disease. A review of current literature highlights mechanisms by which cortisol impacts neuronal plasticity, dendritic architecture, neuroinflammation and connectivity within brain networks. Methodological issues in human research—such as measurement of cortisol, imaging techniques, and controlling for confounders—are addressed. A hypothetical research design is proposed for investigating cortisol’s effect on functional connectivity in young adults exposed to chronic psychosocial stress, employing salivary cortisol assays, fMRI resting-state scans, and cognitive assessments. Expected outcomes include associations between higher cortisol reactivity and reduced connectivity in PFC networks, along with poorer executive performance. The findings underscore the importance of integrative approaches combining endocrinology, neuroimaging and cognitive neuroscience to understand the neurobiological consequences of stress. The article concludes by discussing implications for stress management, prevention of brain dysfunction, and potential interventions aimed at modulating cortisol dynamics to preserve brain health. Keywords: cortisol, brain, hippocampus, prefrontal cortex, amygdala, stress, nervous system, neuroplasticity, cognitive function, neurodegeneration.

Cortisol, brain, hippocampus, prefrontal cortex, amygdala, stress, nervous system, neuroplasticity, cognitive function, neurodegeneration.

Harrewijn A, Vidal-Ribas P, Clore-Gronenborn K, et al. Associations between brain activity and endogenous and exogenous cortisol – a systematic review. Psychoneuroendocrinology. 2020;120:104775.

Ouanes S, Popp J. High cortisol and the risk of dementia and Alzheimer’s disease: a review of the literature. Frontiers in Aging Neuroscience. 2019;11:43.

Ouanes S, Popp J. Interrelationships between cortisol, cognition and dementia : A review of the literature and new own findings. European Psychiatry. 2020;41(S1).

Chaminade T, et al. Neurobiological implications of chronic stress and metabolic dysregulation in inflammatory bowel diseases. Biomedicines. 2022;10(9):220.

The cortisol axis and psychiatric disorders: an updated review. Pharmacological Reports. 2025.

Neurobiological effects of perceived stress are different between adolescents and middle-aged adults. Brain Imaging and Behavior. 2020;14:1888-1901.

Lasting effects of stress physiology on the brain: Cortisol reactivity during preschool predicts hippocampal functional connectivity at school age. Developmental Cognitive Neuroscience. 2019;[e-pub ahead].

Hypertcortisolism in the brain, a highly dynamic process with stable and detrimental consequences. The Journal of Clinical Endocrinology & Metabolism. 2020;105(5):e2084.

Stress, while a natural part of life, can affect brain structure and function (Verywell Mind).

Stressed-Out People May Have Smaller Brains, Study Says. TIME. 2018.

“10 weirdly specific signs you have high cortisol because of stress” (NY Post).

“Cortisol: everything you need to know about the ‘stress hormone’”. The Times. 2024.

Research on functional connectivity during emotion processing in women with depression: cortisol effects. Psychoneuroendocrinology. 2021;129:105271.

Stress monitoring using low-cost EEG devices: linking neuro-markers to cortisol. (Preprint) 2024.