Understanding Hyperarousal and Hypoarousal: What’s Happening in Your Nervous System?
Please note that this blog post reflects the author’s perspective is not a substitute for individual therapy or support. If you need immediate support, please connect with your local crisis support (such as calling or texting 9-8-8 within Canada) or emergency services (such as 9-1-1).
Have you ever felt completely on edge, like your mind won’t stop racing and you can’t seem to relax? Or perhaps you notice that you often feel numb, detached, or too exhausted to be present to what’s happening around you.
Whether you notice that you are often in one of these states or find yourself oscillating between the two, these are signs that your nervous system may be outside of its optimal range — also known as the window of tolerance — and instead in survival-focused patterns of hyperarousal or hypoarousal.
Understanding the difference between these two nervous system states can help you make sense of your reactions to stress, anxiety, and trauma. Let’s explore what hyperarousal and hypoarousal mean, how they show up in everyday life, and what’s happening inside your nervous system when you experience them.
What Is the Window of Tolerance?
The Window of Tolerance, a term coined by Dr. Dan Siegel, refers to the range in which we can handle stress and emotions without becoming overwhelmed. When we’re within this window, we feel grounded, present, and capable of responding to challenges. We might feel stressed, anxious, or upset, but can tolerate being present with these emotions. However, when we experience something that is too much for us to handle without overwhelm, our nervous system shifts outside of this window into either hyperarousal (above the window) or hypoarousal (below the window).
When we’re in our Window of Tolerance, our prefrontal cortex — the part of our brain responsible for rational thinking and creative problem solving — stays online. But when we move outside the Window of Tolerance, our survival responses take over. These survival responses – fight, flight, freeze, and submit – are not conscious choices but often automatic patterns of feeling, sensation, and behaviour.
Hyperarousal: The Fight-or-Flight State
Hyperarousal occurs when our sympathetic nervous system is activated. In this state, our body and mind are on high alert, ready to respond to perceived danger. This is often referred to as the fight-or-flight response.
Some Signs of Hyperarousal
Feeling emotionally overwhelmed
Racing thoughts or overthinking
Panic attacks or anxiety
Hypervigilance (constantly scanning for danger)
Impulsive or reactive behavior
Difficulty sleeping
What’s Happening in Your Nervous System?
When the amygdala (the brain’s alarm system) perceives a threat, it activates the sympathetic nervous system. This triggers the release of adrenaline, increasing our heart rate and breathing to prepare the body for action. The body is ready to fight or flee.
While this response is helpful in real danger, it can be confusing when activated in everyday situations. For example, if we’ve experienced trauma, our nervous system may become hyperalert, even when there is no immediate threat. We might feel the need to overperform at work, constantly try to please others, or avoid conflict at all costs — not because we logically want to, but because our nervous system perceives these situations as dangerous.
Hypoarousal: The Freeze or Shutdown State
Hypoarousal happens when the parasympathetic nervous system dominates. In this state, we may feel disconnected, numb, or unable to take action. It’s often referred to as the freeze or submit response.
Some Signs of Hypoarousal
Feeling foggy or numb
Difficulty thinking or making decisions
Feeling disconnected from emotions
Low energy or exhaustion
Passivity or compliance
Oversleeping or overeating
What’s Happening in Your Nervous System?
When our nervous system perceives that fighting or fleeing isn’t possible or a safe option, it shifts into hypoarousal to protect us. This is a survival mechanism — a way of ‘playing dead’ or submitting to avoid further harm. The body slows down, our heart rate decreases, and we may feel a sense of emotional shutdown.
When we have had a history of trauma where we felt stuck or where taking action didn’t feel safe or possible, hypoarousal can become a chronic state. We might feel unable to take action or assert ourselves, even when we want to. This can show up as, for example, not saying no to something that doesn’t feel right to us, not because we truly agree, but because our nervous system has learned that it is threatening or dangerous to go against what others have expressed.
Trauma and Nervous System Dysregulation
When we are children, our Window of Tolerance is not very big. Our brain is still developing, and along with it, our ability to tolerate emotions. We rely on adults around us to help us develop our emotional muscles, and in turn, increase our ability to tolerate stress and big emotions. In other words, when we are children, our Window of Tolerance is not very wide and we rely on those around us to help us expand it.
However, when we have not had consistent connection with safe and attuned adults to build these emotional muscles, our Window of Tolerance may not have had an opportunity to grow to be wide enough to tolerate stress and big emotions as adults without feeling overwhelmed.
Additionally, when we have experienced trauma or a traumatic environment in the past, having a narrow Window of Tolerance – that is, a nervous system that is sensitized to quickly detect and respond to danger or threat through hyperarousal or hypoarousal responses – was adaptive to us making it through the situation or environment. This means that we may not have had the opportunity to widen our Window of Tolerance because our system was focused on surviving.
When we haven’t had the chance to expand our Window of Tolerance or strengthen our emotional muscles, it means that our system shifts into survival responses (think fight, flight, freeze, submit) quickly. This can show up for us in our everyday lives as adults in ways that leave us feeling confused or out of control. We may experience feelings or behaviours that we don’t feel logically fit the situation or that aren’t aligned with the people we want to be, yet feel like we don’t have control over doing something differently. When we aren’t aware that our system is in chronic survival patterns of hyperarousal or hypoarousal, it is really common to feel down on ourselves, feel hopeless, or feel like there’s something wrong with us. We might see ourselves as “just being anxious” or as “being lazy or unmotivated”.
However, when we think about these automatic feelings and behaviours in the context of how the nervous system works, we can begin to understand that these reactions aren’t defects or flaws or character traits – rather, they are patterns of automatic survival responses that once had a big role in keeping us safe or getting through difficult things.
Moving Toward a Regulated Nervous System
The goal is not to eliminate hyperarousal or hypoarousal — these states are natural and sometimes necessary. Instead, the goal is to build our emotional muscles and expand our window of tolerance so we can stay more grounded and present, even when faced with stress or triggers.
Some Ways to Start Building your Emotional Muscles
Start Small: Take small steps, for example, if trying the ideas below or in my previous posts. Know that you can pause at any time, and choose to come back to an activity if it feels overwhelming.
Notice Your State: See if you can invite some curiosity when feelings of anxiety, overwhelm, or disconnection are present. Maybe you can curiously ask yourself, “Where am I above, within, or below my window of tolerance?” You can learn more about different ways to notice which state you are in within my previous post.
Grounding Techniques: Practices like deep breathing, progressive muscle relaxation, or sensory grounding can help bring your nervous system back toward the window of tolerance.
Seek Support: Connecting with support such as therapy can help you recognize your nervous system patterns and learn strategies to regulate your responses.
From Automatic Survival Pattern to Awareness and Agency
Recognizing the difference between hyperarousal and hypoarousal can empower you to better understand your anxiety, people-pleasing tendencies, and trauma responses.
With practice and support, you can build new habits and ways to respond to stress from a place of more choice rather than automatic survival mode.
I know first-hand that deciding to be curious about our automatic nervous system patterns can feel really scary or difficult. I also know first-hand that it can be really, really rewarding.
About the Author
Sabrina Sibbald (MSW, RSW) is a Registered Social Worker and Psychotherapist. She supports adults in Burlington, Toronto, and across Ontario to overcome anxiety, people pleasing, and trauma so they can move forward in a way that feels true to who they are.
References
Fisher, J. (2021). Transforming the Living Legacy of Trauma Workbook.
Fisher, J. (Flip Chart). Psychoeducation Tools for Trauma-Informed Therapy.
Ogden, P. (2006). Sensorimotor Psychotherapy: Interventions for Trauma and Attachment.
Siegel, D. (1999). The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are.
