Effects of Stress On The Brain: How stress can affect the human brain in different stressful situations 

By: Maryam Abro


To understand the common feeling of “stress” on the human brain, we need to understand the definition.

Carter (2007) defines stress as:

“A person-environment, biopsychosocial interaction, wherein environmental events (known as “stressors”) are appraised first as either positive or unwanted and negative. If the appraisal is that the stressor is unwanted and negative, some action to cope and adapt is needed. If coping and adaptation fail, one is to experience stress reactions.”

Stress is a result of uncertain, adverse, random, and overwhelming events. Stress is  greater if there are already problems and struggles in one’s life. Stress reactions arise regardless if stressors are “objective” or “subjective” and long-term exposure can result in negative psychological consequences, ranging from mild to severe.

It is believed by Carlson, (1997), that people who are experiencing severe stress react in one or more of the three fundamental reactions that are presented by one or more “physiological, emotional, cognitive, or behavioral modalities. The core reactions are:

  1. Intrusion or reexperiencing
  2. Arousal or hyperactivity
  3. Avoidance, or maybe even physical numbing”

Unfortunately, stress is a word used frequently in modern-day society, often used to describe the experiences that cause anxiety and frustration because they make individuals feel insecure and leave them with the feeling that they wouldn’t be able to successfully cope with situations that they may be facing. 

 Nowadays, there are many different stressors, especially during the Covid-19 global pandemic. Some of the stressors that may occur due to Covid are new rules causing changes and making new normal for individuals, social distancing, problems at an individual’s job or home, financial worries, etc. It is certain that these stressors would be, or have been deeply amplified due to our current circumstances with Covid-19 as well. Sometimes, these stressors can have serious implications, for example, effects of social distancing and isolation on mental health, loss of livelihood because of shutting down businesses, deaths caused by drugs and alcohol during the pandemic, increase in domestic violence, etc. Also, they may trigger the human “flight or fight response”. Besides creating daily annoyances in life, these stressors can lead to chronic stress, or maybe even PTSD (post-traumatic stress disorder), which is an aftereffect of a tragic experience.

The life experiences described above are the most common stressors that trigger human beings and cause their behavior to change in a certain way. For instance, being “stressed out” may create anxiety and depression, insomnia, and excessive substance abuse like drinking, or smoking. Some individuals may even resort to using medications such as “anxiolytics”, benzodiazepines, and sleeping pills to get rid of stressful thoughts. The prolonged use of such self-medication can result in various negative health outcomes.

The human brain itself is responsible to select the experiences that cause stress and it also categorizes the behavioral and physiological reactions to the stressful events, which can promote or deteriorate health. Acute and Chronic Stress has been shown to cause changes in the brain and affect many systems in the body like “neuroendocrine, autonomic, metabolic, cardiovascular, and immune”. 

As discussed earlier, it is well believed that stress causes changes in the brain. Now, the question at hand is: what Kind of change does stress cause in the human brain? To find out what kind of changes take place in the human brain, we need to explore the effects of stress in different parts of the brain. 

Extreme Acute and chronic stress may cause effects on the amygdala’s stress response through three core regulatory systems: “the serotonergic system”, “the catecholaminergic system” and the “HPA axis”.

The advancement of brain imaging techniques has enabled researchers to examine the neural circuit activity changed by acute stress in humans. MRI studies have revealed that the subjects who listened to stressful events related to their life had increased response of blood oxygen level-dependent (BOLD) in the medial PFC (anterior cingulate cortex), particularly in the right hemisphere indicating the anterior cingulate cortex’s part in processing mental suffering. Studies conducted on humans also reported how drastic stress affects the dlPFC operations, participants who had been exposed to stressful videos, displayed poor performance of N-back working memory, and reduced BOLD activity over dlPFC. Results also revealed that severe stress ended the normal deactivation of the default mode network. The subjects who had greater levels of catecholamine had more stress causing damage to working memory performance and reduction in dlPFC activity. There is a correlation between stress-induced catecholamine release and poor working memory performance. Exposure to unmanageable stress and higher catecholamine levels together impair the higher cognitive functions of PFC.

The hippocampus performs some of the higher tasks in the brain, such as encoding, storing, and retrieving information.  Once it receives the messages from the axons, this information is processed through different synaptic mechanisms. The hippocampus sorts out the information and differentiates between important and less important information. Exposure to acute stress makes the hippocampus open to attack. Minor and short-duration stress normally increases hippocampal operation by increasing “synaptic plasticity”.

Stress impacts learning and memory tasks in humans and animals by changing the structure of hippocampal neurons . These alterations occur in different stages, starting from the changes in the synaptic memory to the changes in the dendritic branches . Most drastic effects of long-lasting stress on the hippocampus is a decrease in the pyramidal cell dendrites branches. The amount and form of “synapse-bearing spines” are active and are controlled by “factors including neurotransmitters, growth factors and hormones that, in turn, are governed by environmental signals, including stress”.

The information discussed above highlights some of the crucial structures of the brain and their response to stressful events. Many other areas need to be examined in this connection, such as loss of synaptic connections, dendrites, spine and “the generality of the stress response to other high-ordering association cortices, and how genetic insults interact with stress signaling pathways to hasten disease”. Stress and its effects on the brain is a vast area of research. The crucial point for future research is to unravel how different mechanisms few of those mentioned above (CRH, neuropeptides, neurotransmitters) respond to stress hormones such as adrenal and stress-associated neurotransmitters. It could be a challenging task to study the joint role played by these mechanisms to alter the hippocampus in response to stress. Further research would be required to uncover some of the effective treatments and helpful approaches to handle the drastic effects of both acute and short-term stress.