Hyperarousal and Hypoarousal After Trauma
When people picture PTSD, they often imagine someone who is constantly on edge. They might think of panic, nightmares, flashbacks, anger, or being easily startled.
Those can absolutely be experiences of PTSD. But trauma does not always make the nervous system feel more activated.
Sometimes, it does the opposite.
A person may feel numb, disconnected, exhausted, foggy, or far away from themselves and the world around them.
These experiences are often described as hyperarousal and hypoarousal. They are not separate diagnoses or official subtypes of PTSD. Instead, they are useful ways of understanding how our nervous systems may respond when something feels overwhelming or unsafe.
Hyperarousal: When Your System Is Doing Too Much
Hyperarousal happens when the nervous system is highly activated and prepared to respond to danger.
You might experience:
- Feeling anxious or on edge
- Irritability or anger
- Difficulty sleeping
- Racing thoughts
- Feeling easily startled
- Difficulty sitting still or relaxing
- Constantly watching your surroundings
- Feeling like something bad is about to happen
- A racing heart, muscle tension, or other physical signs of stress
In this state, your nervous system is essentially saying: “Something might happen. I need to be ready.”
This response makes sense during danger. The problem is that after trauma, the nervous system may continue responding as though danger is present even when the immediate threat has passed.
Hypoarousal: When Your System Shuts Things Down
Trauma can also produce a very different response.
Instead of becoming more activated, the nervous system may become less activated. This is often called hypoarousal.
You might experience:
- Emotional numbness
- Feeling disconnected from other people
- Feeling detached from your body
- Difficulty thinking or concentrating
- Feeling exhausted or heavy
- Going blank during stressful situations
- Feeling like you are just going through the motions
- Feeling unreal or as though the world around you is unreal
- Difficulty accessing emotions
- Rather than preparing you to fight or escape, your system may try to protect you by reducing how much you feel or experience.
The message becomes something closer to: “This is too much. I need to shut some of this out.”
Some forms of this disconnection are called dissociation. PTSD can include a dissociative presentation involving experiences such as depersonalization, feeling detached from yourself, or derealization, feeling as though the world around you is unreal or dreamlike.
You Can Experience Both
Hyperarousal and hypoarousal are not personality types, and you do not necessarily belong in one category.
Many people move between the two.
You might feel anxious and hypervigilant throughout the day and then completely shut down afterward. You might become intensely activated during conflict and suddenly go blank. Or you might generally feel disconnected until something reminds you of a traumatic experience and your nervous system rapidly shifts into high alert.
This is one reason trauma can feel confusing.
You may wonder: “Why am I overreacting sometimes and feeling absolutely nothing at other times?”
Both experiences can be attempts by the nervous system to manage something it has learned to perceive as overwhelming.
The Window of Tolerance
One way therapists conceptualize these experiences is through the window of tolerance.
Inside this window, you can experience emotions without becoming completely overwhelmed or shutting down. You can think, feel, communicate, make decisions, and remain connected to what is happening around you.
Above the window is hyperarousal.
Below the window is hypoarousal.
Trauma can make that window feel very small. Experiences that other people seem able to tolerate may quickly push your nervous system into high alert or shutdown.
Trauma therapy is not simply about making difficult feelings disappear. Part of the work can involve gradually increasing your ability to stay present with thoughts, emotions, memories, sensations, and relationships without becoming overwhelmed or disconnected.
Over time, the goal is not to never become activated again.
It is to develop greater flexibility.
To notice what your nervous system is doing, understand why it may be happening, and have more options for responding when it does.
Sometimes healing looks like learning how to calm down, other times it looks like learning how to safely come back online.
Resources with more information about PTSD:
