The human stress response is adaptive. Everything that goes on in the brain and body has one core interest in mind–ensuring you stay alive and successfully adapt to changing conditions, even stressful conditions. 

Allostasis ensures that various systems turn up and down to match the demands of the world around us. 

Therefore, our stress response will continue responding for as long as is needed to match the demands of the outside world, for as long as the stressor is present.

When we confront stress or a threat, the brain and body mobilize the defensive responses we discussed before. 

And when the stressor does not go away, the body will continue responding to that stressor and its constant presence. 

Think for a moment. The stress response is similar to a faucet. Faucets are designed to make water available quickly and efficiently whenever needed. You can turn the faucet on, releasing all the water you need, and when you no longer need water, you can turn it off tight. 

A faucet also has a sort of allostasis. It constantly adapts to the needs of the environment, turning on fully, turning on a little bit to release just a trickle, or turning off to stop the water flow. The faucet, like the stress response, is always ready when needed, to the degree needed.

But, faucets are not supposed to be left on. A faucet left on will drain all the water from the tank. A faucet left on will damage the walls or floor, corrupting the foundation of the house or flooding the garden. 

The stress response system functions similarly. When stress or threat come our way, the brain and body adapt and adjust all our systems–including the HPA axis and the autonomic nervous system–to confront the current and immediate situation until things once again change. 

For many people, the stress they confront in their lives comes and goes in waves. 

Stress exists for a short period of time and then fades away into more calm or “normal” circumstances. 

For many people, stress is abnormal, an aberration from their daily lives. 

Unfortunately though, sometimes stress stays. Sometimes, the source of stress does not go away. The stressor or threat does not pass and lingers for a long time. 

In this case it is called chronic stress, which is the stress that does not dissipate.

In such cases, the stress response remains turned “on.” The faucet stays open. 

In situations of chronic stress, systems are turned on high for extended periods of time. 

• The HPA axis is hyperactive. 
• The sympathetic nervous system is hyperactive. 
• Bodily systems operate in “stress mode” for extended periods of time.

And while the brain and body’s initial response to stress and threat help us cope temporarily, a continuation of the stress response over an extended period of time can end up having some negative, unwanted, and unintended consequences. 

Let’s have a look together at what exactly goes on when stress becomes chronic.