Understanding stress as a feedback loop

by Valtteri Wikström

Stress plays an important role in everyday functioning. Healthy stress directs us to act and to deal with what is happening around us. Anytime we encounter a stressor our body activates, our energy increases, and our focus improves to a suitable level for us to deal with the situation.

The "stress hormone"

Our brain and nervous system controls the appropriate level of stress through the production of cortisol. Cortisol is a hormone, a naturally occuring substance in the human body, produced by the adrenal gland. When cortisol gets released, additional energy reserves become available, preparing the body for action. Cortisol gets released based on the magnitude of the stressor. If the stressor is large, the amount of cortisol released is also higher.

Encountering an immediate and grave danger, like a dangerous beast, pumps our body full of cortisol and we spring into action, we enter a mode of fight or flight. On the other hand, a small stressor, such as unexpectedly encountering a small rodent, might only trigger a small response that allows us to identify the animal and determine that no further action is needed. Similarly, physical injury leads to an increase in cortisol production in proportion to the severity of the injury. Cortisol reduces inflammation and increases blood flow to the injured area to facilitate healing.

The release of cortisol makes sugar available for cells to use as fuel, which is known as a catabolic state. Bodily and mental activation as a response to the stressful situation uses up the sugar. Quickly accessible sugar reserves are limited, and if the stress becomes prolonged, the body starts to crave quick sources of fuel in the form of sugary and fatty foods.

The healthy stress system is a negative feedback loop

Cortisol limits its own production. Once cortisol gets released, it acts to suppress the same neural pathways which control its release. This leads to a negative feedback loop, returning the body to a more energy conserving state once the stressor has been dealt with. Like an automatic kettle which turns off once water starts to boil.

The healthy stress response has a transient nature, meaning that once the appropriate activation level has been reached, the stress subsides and the body can return to a resting state. This mechanism is extremely important for the replenishment of energy reserves, which have been used up during the stress reaction.

Stress-related disorders disrupt the cortisol system

Sometimes the stress system goes into a dysfunctional state, usually involving excess cortisol production. In post-traumatic stress disorder (PTSD), an enormously stressful event such as a severe danger, accident, or injury, creates such a strong memory imprint, that an excessive stress response becomes triggered by stimuli that are related to the memory. Sometimes the response can occur also to seemingly unrelated stimuli that happen to activate the relevant memory pathways, or even spontaneously.

Anxiety and stress are deeply related. In some sense, anxiety is the state in which the body is expecting stress. Anxiety could be seen as a base level of cortisol production, keeping the mind vigilant and the body ready for action. Constant anxiety due to a stressful environment, PTSD, prolonged stress, or other causes such as major depression, is due to the transient stress system having become broken.

Stress system malfunction occurs when the neural pathways initiating cortisol production are constantly active, and the feedback pathways which allow cortisol to limit its own production become resistant to cortisol itself. This leads to the negative feedback loop becoming inactive or even turning into a positive feedback loop. If the feedback loop becomes positive, stress itself leads to even more stress. When this type of self-reinforcing loop is created, "the kettle boils over", leading to disproportionate and uncontrolled reactions, such as panic attacks, extreme anger, or debilitating sadness.

A result of both an inactive and a positive feedback loop is a constant production of cortisol on a higher than usual level. The constant flow of cortisol keeps the body active without breaks, making it hard or impossible to enter into a resting state. In turn, this hinders energy conservation and the replenishment of energy reserves. The end result is a constant strung-out fatigue, trouble sleeping, shortened temper, lowered cognition, feelings of anxiety, depression, as well as a weakened immune system.

How to manage stress

Properly managing psychological stress needs to take into account also physical wellbeing. Cortisol teaches us that the same system is activated in response to both physical and psychological stressors. In a very real sense, they are both using the same reserves, and their effects cumulate.

To keep functioning at an optimal level, it is important to recognize the telltale signs of excessive stress. Some of these signs are an inability to relax, sleeping issues, fatigue, headaches, muscle tension, digestive issues, and increased anxiety. Early recognition of excessive stress followed by preventive action shortens the recovery time and decreases the risk and seriousness of disability.

Often the best first aid to a disrupted stress system is relaxation in a calm and safe environment. Hydrating and replenishing the body's reserves with nutrient-rich food is important. Stressing the body through heavy exercise has a risk of increasing cortisol production and depleting the energy reserves further, but calm movement and activity, especially in a safe and familiar social setting can be very beneficial to wind down. The aim is essentially to eat and sleep, but non-demanding activity can help to calm the stress response and make this possible.

After proper rest and a full sleep, the cortisol system has had an opportunity to reset and the body has restored its energy reserves. This energy is best used to evaluate the situation and determine whether the initial recovery has been successful. If the immediate stress reaction has subsided, now is a good time to do actions to target the root causes of the stress, and consider further treatment for example in the form of therapy, diagnosis, and/or medical leave.