Bite-Sized Neuroscience of Cortisol and Stress (or Why Does Stress Management Matter?)
The Role of Cortisol in the Stress Response
The brain regulation mechanisms involve neuroendocrine and neurohormonal processes that adjust levels of arousal or alertness. Cortisol, often referred to as a ‘“stress” hormone , plays a prominent role in these processes. It belongs to the corticosteroid group of adrenal steroids produced by the adrenal glands.
A stressful situation triggers a signalling cascade in the brain, from the prefrontal cortex (PFC) or limbic regions (including the amygdala and hypothalamus) to the hypothalamic-pituitary-adrenal axis (HPA), which is the main hormonal stress-response system. This signalling results in an increased release of cortisol, which is known as a ‘’stress hormone’’. The function of cortisol is to prepare the body for action in response to stress. Its effects include increased blood pressure, elevated blood sugar and suppressed immune system.
Effects of Stress-Evoked Cortisol on Cognition
“Stress” commonly refers to feeling frustrated, anxious and overwhelmed due to circumstances in which we cannot cope effectively. Accordingly, stressors are those factors that provoke our inability to adjust to or manage a stressful situation and cope effectively. The stress factor induces a response such as hormonal release and other mediating processes. This reaction can promote coping when the response is successfully switched off or evoke pathological reactions when the stress response is overlong. It is the case that even though the originating stressor passes, the pathophysiological reaction can continue beyond.
Stress causes complex structural alterations in various brain regions. It can generate either plasticity-improving reactions related to enhanced cognition or toxic reactions that lead to impairments in brain functioning. These reactions depend on the form, saturation and duration of the stressful episode. Experiencing a lot of stress, cortisol can be elevated or over-secreted.
Stress-evoked release of cortisol leads to several changes in glutamatergic neurotransmission. Glutamate is the main excitatory neurotransmitter in the brain, highly concentrated within the central nervous system (CNS). Stress causes a rapid increase in glutamate release in the prefrontal cortex (PFC) and hippocampus in the brain. Thus, cortisol particularly affects those parts of the brain involved in cognition and thinking (PFC) and remembering (hippocampi).
The Impact of Acute and Chronic Stress on Brain Function
In terms of acute stress (over hours, short-term), both higher levels of glutamate and augmented glutamate receptors could promote adaptive responses to stress and enhanced cognitive processes, facilitating classical conditioning, working memory and associative learning. Adaptive responses refer to a biologically ‘tuned’ system allowing survival and thriving in a constantly changing environment.
However, in the condition of chronic stress (over days and longer), increases in cortisol result in excitotoxicity and damage to brain cells. Glutamate becomes toxic to brain cells as, chronically, glial cells can not clear the overabundant neurotransmitter from the extracellular space. Raised cortisol levels and increased glutamate released over the long term cause alterations in cell gene expression resulting in shrinkage and reduction of dendrites and a reduction of spine synaptic density on nerve cells in the PFC.
Long-term or chronic stress-induced cortisol elevations may become a pathophysiological mechanism causing various critical alterations. These changes have been observed in the brains of people with stress-related psychiatric illnesses, such as anxiety disorders and depression, leading to mental health struggles, relationship problems and other difficulties. In addition, chronic cortisol release weakens the immune system by diverting responses away from anti-inflammatory processes to instant needs. As a result, our immune system is impaired, leading to getting colds, catching the flu and other infections. This highlights that cortisol is essential for immune response and other critical systems but only in the right amounts.
The Importance of Managing Stress at Home and Work
Resolving difficulties that cause stress at home and work is often a challenge. Moreover, it is sometimes impossible without the professional guidance of a counsellor, psychotherapist or stress-management coach to develop proper coping strategies or even change your lifestyle. But it is worth the effort. Preventing chronic stress keeps cortisol levels fine-tuned, leading to a strong immune system, good sleep, motivation, improved metabolism and memory and reduced pain sensitivity. These factors are crucial to prevent illness and to maintain a pleasurable life.
HPA Axis Image by brgfx on Freepik
