The Window of Tolerance


Key points:

  • Trauma is a breakdown in our ability to make sense of our experience
  • Making sense of our experience is dependent out our mental capacity
  • Mental capacity changes depending on our arousal level; it is highest when we are inside our Window of Tolerance and declines greatly when we are outside our Window of Tolerance
  • Trauma, overwhelming emotional experiences and chronic stress tend to narrow our Window of Tolerance, and therefore our mental capacity
  • With a narrowed Window of Tolerance, we are more prone to emotional dysregulation, anxiety, panic, depression and dissociation
  • A key first step in treatment is expanding the Window of Tolerance in order to increase mental capacity. This both reduces symptoms and helps clients to tolerate the emotional memories enough to work though them in therapy

Recently, I wrote about redefining trauma as a psychological process - or, more specifically, the failure of a psychological process - rather than an event.

Under normal circumstances, our brain links together sensory, emotional and cognitive data to make sense of our experience. This process is dependent on our mental capacity to link these different pieces of information together.

Trauma is a “system overload” that causes this process to beak down. 

Trauma overwhelms our mental capacity to take in, interpret and and make sense of what’s going on. 

Which begs the question, what determines our mental capacity?

Just like everything else biological, our nervous system has an ideal climate; a Goldilocks zone in which it operates best. This zone is called the Window of Tolerance. 

Sandwiched between the chaotic arctic pole of hyperarousal and the barren antarctic shelf of hypoarousal, the Window of Tolerance is that temperate area around the equator. Within the Window of Tolerance, our mental capacity is optimized. Information flows smoothly between the different processing centres of the brain, we are able to process and integrate information, and can respond to situations appropriately. While our level of arousal rises and falls throughout the day depending on the circumstances (that deep sigh of relief when you get home after a long day, that moment of alarm when you realize you have company coming for dinner and have no groceries), the fluctuations are moderate and adaptive, prompting the appropriate response (a glass of wine on the couch, a fast-paced jaunt to the store).

Above and below our Window of Tolerance, our mental capacity rapidly diminishes. 

When we are hyperaroused, the system is flooded with more information than it is able to process and integrate. Without the ability to organize, interpret and make sense of our experience, the system is rapidly overloaded. Sensing a threat, our defensive operating system is triggered and our active survival responses (fight, flight, freeze) take over, leaving us feeling enraged, irritable, anxious or panicked.

If left unresolved, this hyperarousal often plummets into hypoarousal, which can be thought of as a type of burn-out that follows the energy-intensive hyperarousal state. We are still unable to process and integrate our experience, but with our active survival responses not having rectified the situation, we turn to our passive survival responses (submit, collapse, dissociate). When we are hypoaroused, the system is essentially tuning out the internal chaos, leaving us feeling numb, cut off and depressed.

All of this is very adaptive if, in fact, the threat is real. 

The difficulty is that those who have experienced trauma, persistent stress and chronic attachment inadequacies tend to have a narrowed Window of Tolerance. 

They have, in effect, been taught that the world is not safe, and therefore have set their barometer for adaptive survival actions fairly low. In a world that is not safe, having a defensive operating system with a hair-trigger is the best way to survive. Even more significant, being in the Window of Tolerance may not actually feel safe because the nervous system has learned that this is where you’re vulnerable. 

This narrowed Window of Tolerance often causes people to routinely misinterpret innocuous situations as dangerous, leading to the experience of their system continually being hijacked by defensive operating systems.

The relationship between the Window of Tolerance and our ability to make sense out our experience makes it a key element of treatment. If we have a narrowed Window of Tolerance or do not feel safe inhabiting it, we will not have the mental capacity to work through the events that have led us here. Instead, the traumatic memories will overload our mental capacity, push us outside our Window of Tolerance and lead us into the realms of re-experiencing the trauma, rather than working through it.

Recalibrating the nervous system to expand the Window of Tolerance not only reduces the symptoms of emotional dysregulation, such as anxiety, panic, dissociation and depression, it also opens the door for the deeper work of healing the emotional wounds that caused its narrowing in the first place.