What exactly is hypoarousal, and how does it differ from hyperarousal? In my experience as a clinician, understanding these nervous system states can empower you to regain a sense of control over your body’s responses. By learning about the nervous system, you can better observe what’s happening within and respond to your body’s needs in the moment.

In this article, we’ll explore hypoarousal, hyperarousal, and the window of tolerance. With this understanding, you can start tracking your nervous system and introducing practices that expand your capacity to stay present, grounded, and engaged. And if you’re looking for more of a deep dive, check out our comprehensive article on nervous system basics.

The Window of Tolerance

Before diving into hypoarousal and hyperarousal, it's helpful to understand the concept of the window of tolerance. This is a way to think about our capacity to handle intense emotions and stress.

When we’re within our window of tolerance, we’re able to navigate life’s challenges with resilience and adaptability. In this state, our sympathetic nervous system (which helps us respond to stress) and parasympathetic nervous system (which helps us rest and recover) work together harmoniously. This balance allows us to stay present, calm, and engaged, even in the face of stress.

A large window of tolerance means you have a greater capacity to manage stress and emotions without becoming overwhelmed. It’s like driving a car smoothly, with the gas and brake pedals working in sync. However, when stress exceeds what we can handle within this window, we may become dysregulated, leading to either hyperarousal (where we’re revved up and anxious) or hypoarousal (where we shut down and disconnect).

For example, when you’ve had a good night’s sleep, eaten well, and moved regularly, you likely notice it takes more stressors to cause you to "blow a fuse." This is because your window of tolerance is wider, giving you more capacity to handle challenges without becoming overwhelmed.

Let’s explore what happens when we move beyond our window of tolerance.

Hypoarousal

When people think of stress, they often imagine the fight-or-flight response. But our bodies have another way of coping with overwhelming stress—by slowing down into a state of hypoarousal. This is when our nervous system essentially hits the brakes, lowering overall activity to protect us from too much stimulation.

Hypoarousal can show up in different ways. Some people might feel mildly foggy, disconnected, or fatigued, while others might experience more intense symptoms like dissociation. It's important to note that hypoarousal is different from the freeze response, which involves both sympathetic and parasympathetic activation and leads to full-body immobilization.

For example, when I experience sensory overload, my body shifts into a hypoarousal state. My senses dull, I feel heavy and tired, and a sense of fogginess takes over. This is a mild form of hypoarousal, but for many ADHDers and Autistic individuals, sensory overload can push us out of our window of tolerance and into this state.

Let’s take a closer look at the signs of hypoarousal.

Traits of Hypoarousal

Mental and Emotional Traits:

• brain fog

• dissociation

• lack of focus

• sleepiness

• fatigue

• shut down

• low energy

• numbness

• depression

• technology addiction

• cravings for substances

Physiological Traits

• irregular heartbeat

• shallow and irregular breathing

• digestive issues

• over or under-active immune system

• sensitivities to the cold

Purpose of Hypoarousal

Hypoarousal occurs when the body slows down in response to overwhelming stress. It’s as if your nervous system is saying, “This is too much; let’s power down for a while.” This response can manifest as fatigue, numbness, or a sense of disconnection. Unlike the freeze response, hypoarousal isn't about immediate survival; it's more about conserving energy when stress becomes too much. In today’s world, hypoarousal might kick in during less threatening situations, like work stress, leading to unhelpful shutdowns.

In modern life, hypoarousal often kicks in during prolonged stress, leading to feelings of being stuck or unmotivated. For instance, facing an overwhelming project might trigger a shutdown, making it difficult to start. Though maladaptive in contemporary contexts, recognizing hypoarousal as the body's attempt to manage stress can foster self-compassion and encourage strategies to expand one’s window of tolerance.

Even though hypoarousal may be less adaptive now, it's still the body's way of protecting itself. Recognizing this can foster self-compassion and encourage strategies to expand your window of tolerance.

Hyperarousal

When we enter a hyperaroused state, our sympathetic nervous system kicks into high gear. This means we’re mobilized to either confront a threat (fight) or escape from it (flight). In this state, we become hypervigilant and energized, but often also anxious or reactive.

Traits of Hyperarousal

Mental and Emotional Traits

• panic

• fear

• worry

• irritation

• anger

• frustration

• impulsivity

• high energy

• stress

• aggression

• anxiety

• reckless behavior

Physiological Traits

• fast heart rate

• shallow and quick breaths

• high blood pressure

• high levels of cortisol and adrenaline

• muscle tension

The Purpose of Hyperarousal

Most people understand the fight-or-flight response as a survival mechanism—it’s what gives us the energy to either confront a threat or escape from it. Whether we’re being chased by a wild animal or facing danger in a city, hyperarousal kicks in to help us survive by boosting our energy, alertness, and physical capabilities.

In the animal kingdom, when an animal escapes a threat and enters a state of hyperarousal, it doesn't just carry that energy indefinitely. For example, imagine an impala that narrowly escapes a lion in the African savanna. Once safe, the impala shakes off the excess energy, literally shaking its body to discharge the built-up stress. This behavior is observed across many species, including squirrels, birds, and even our pets, who may shake, bark, or run around after a stressful event.

Humans also need to release this built-up energy. In various indigenous cultures around the world, practices like singing, dancing, chanting, and drumming serve this purpose. These cultural rituals help discharge the energy of hyperarousal, allowing individuals to return to a state of calm and re-enter their window of tolerance.

Hyperarousal and Modernity

In today’s world, hyperarousal is almost unavoidable. Unlike our ancestors, who faced immediate dangers like predators, we now deal with long-term stressors—work deadlines, bills, and financial pressures—that our bodies aren’t really designed for. Because these stressors are constant, our fight-or-flight response can get stuck in the "on" position, leaving us in a state of hyperarousal with no clear way to release that built-up energy.

Adding to the challenge, many cultural practices that helped our ancestors discharge this energy, like communal dances or rituals, have faded in modern society. Without these outlets, it's easy to remain trapped in a heightened state of stress, struggling to find ways to wind down and return to a more balanced state.

How Large is your Window of Tolerance?

Ideally, you’d have a wide window of tolerance, giving you plenty of bandwidth to handle stressors as they come. But for many people, especially those seeking mental health support, that window can be pretty narrow.

If you grew up in a home filled with constant stress or trauma, your nervous system might have stayed in a heightened state of alert as a protective mechanism. Unfortunately, this can leave you with a smaller window of tolerance in adulthood.

For neurodivergent individuals, like those with OCD, ADHD, or Autism, that window is often more narrow due to factors like vulnerable neurology, sensory sensitivities, and higher rates of victimization.

Similarly, people with PTSD or trauma-related personality disorders may find their window of tolerance limited. It’s important to remember that this isn’t a failure on your part—it’s your body’s way of protecting you based on past experiences.

If you find yourself getting stressed or overwhelmed more easily than others, it’s likely connected to your nervous system, not something within your immediate control. Understanding this can be a powerful step toward self-compassion. And the good news is, with intentional practice, your window of tolerance can be expanded over time.

Nervous System Check-Ins

If you're aiming to expand your window of tolerance and spend less time in hyperarousal or hypoarousal, one way to do this is by getting to know your nervous system through regular check-ins. By observing how your body responds to stress, you can recognize patterns and better understand your nervous system.

For example, if your heart rate speeds up and anxiety creeps in, you might be entering hyperarousal. Taking deep breaths or going for a walk can help bring you back to a regulated state. Alternatively, if you feel foggy and disconnected, engaging in an upregulating activity, like a brisk walk, might help.

While these check-ins and nervous system exercises are valuable, it's important to remember that they don’t replace the deeper work needed to heal underlying trauma, attachment wounds, or chronic stress. Depth work—such as therapy focusing on trauma and emotional processing—is crucial for achieving lasting regulation and resilience.

Start with daily check-ins, taking a moment to scan your body, mind, and emotions. Are you noticing signs of hyperarousal or hypoarousal? Tracking these patterns gives you insight into your stress triggers and provides you with more agency in how you respond to stress.

To dive deeper into this practice and access tools like worksheets for nervous system mapping, you can check out our Nervous System Workbook.

Summary: Hypoarousal and Hyperarousal

When we’re grounded and engaged, we’re in our window of tolerance. But when stress overwhelms us, we can become dysregulated, either hypoaroused (shut down) or hyperaroused (on edge). Recognizing these states is key to expanding your window of tolerance. By regularly checking in with your body, you can start to see patterns and understand what your body needs to regulate itself.

While understanding these states is crucial, it’s just the beginning. For more insights and tools, consider exploring the Nervous System Workbook, which offers in-depth information and practical worksheets to support your journey toward nervous system regulation.

References

Beauchaine, T. P., Gatzke-Kopp, L., Neuhaus, E., Chipman, J., Reid, M. J., & Webster-Stratton, C. (2013). Sympathetic- and parasympathetic-linked cardiac function and prediction of externalizing behavior, emotion regulation, and prosocial behavior among preschoolers treated for ADHD. Journal of consulting and clinical psychology, 81(3), 481–493. https://doi.org/10.1037/a0032302

Bellato, A., Arora, I., Hollis, C., & Groom, M. J. (2020). Is autonomic nervous system function atypical in attention deficit hyperactivity disorder (ADHD)? A systematic review of the evidence. Neuroscience & Biobehavioral Reviews, 108, 182-206.

Beutler, S., Mertens, Y. L., Ladner, L., Schellong, J., Croy, I., & Daniels, J. K. (2022). Trauma-related dissociation and the autonomic nervous system: a systematic literature review of psychophysiological correlates of dissociative experiencing in PTSD patients. European Journal of Psychotraumatology, 13(2).

Fenning, R. M., Erath, S. A., Baker, J. K., Messinger, D. S., Moffitt, J., Baucom, B. R., & Kaeppler, A. K. (2019). Sympathetic-Parasympathetic Interaction and Externalizing Problems in Children with Autism Spectrum Disorder. Autism research : official journal of the International Society for Autism Research, 12(12), 1805–1816.

Gourine, A. V., & Ackland, G. L. (2018). Cardiac vagus and exercise. Physiology, 33(6), 486-487.

Spratt, E. G., Nicholas, J. S., Brady, K. T., & et al. (2012). Enhanced cortisol response to stress in children with autism. Journal of Autism and Developmental Disorders, 42(1), 75-81.