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The Interconnectedness between Stress and Sleep: Dismantling the “Fight or Flight” Response

Written by: Dr. Elaine Lewis, ND



Our ability to have a good quality sleep is directly influenced by our daily and ongoing levels of stress and vice versa. In order to better understand this, I find it helpful to first understand the two main systems that drive our body: the Sympathetic Nervous System and the Parasympathetic Nervous System.


The Sympathetic Nervous System (SNS) is also called the “Fight or Flight” system and is enacted when our body perceives there to be stress of any kind. This system is designed to help us cope with acute, high intensity stress, for example if we were being chased by a tiger or faced with an immediately life threatening situation. In these situations, the “Fight or Flight” system perceives the stressor, signals the brain of this major stressor, and the brain then causes a cascade of responses throughout the body in order to help prepare us for survival.


When “survival” is the brain’s priority, it causes some body systems to get more attention and others to get less. Our heart rate elevates, allowing blood to travel quickly throughout the body. Our blood pressure also elevates, forcing blood to get to the distant places that require it (for example our brain, so we can think more efficiently, and our legs, so we can run quickly). Our vital organs like the brain, heart, and lungs all work to their most efficient levels during survival mode. On the other hand, processes like digestion and relaxation are no longer priorities, and function at reduced efficiency in order to prioritize the acute stress response for as long as the threat is no longer perceived.


This Sympathetic Nervous System is up-regulated anytime there is a perceived stress to the body, so unfortunately it occurs even when that stress is ongoing/chronic and even when that stress is a lower intensity. Think of your daily life and reflect on what your body might be categorizing as stressful. Do you wake up abruptly, anxious about being late or being too tired to tackle the day? Do you rush through your morning routine, quickly running from task to task until you get out the door? Do you sit in traffic, annoyed at the other cars or at yourself for not planning ahead? Are you having to manage others like your kids, your partner, your colleagues and their pace in the morning? Do you move through your work day, juggling email notifications and mini catastrophes? Do you eat your meals in a rush, distracted? All of these mini stressors prompt our body to hang out in “Fight or Flight” and deal with these perceived threats, while preventing activities that reside within the secondary system.


The Parasympathetic Nervous System (PSNS) works in opposition to the SNS. It’s called the “Rest and Digest” system, because it prioritizes these functional areas of the body. Our ability to efficiently process our food through the digestive system and our ability to have a good night’s sleep are both facilitated through this system. Unfortunately both systems cannot work well at the same time, and what’s also unfortunate (but understandable) is that the body will always prioritize the Fight or Flight system at the expense of the Rest and Digest system when it perceives a stress or threat.


This PSNS system allows for restoration and resilience building. Think of the PSNS as the “Ready, Set” before the “Go” that happens in the SNS. Our bodies need sufficient balance between these two systems in order for both to operate optimally. We cannot efficiently handle the constant rush of our SNS, and in times of chronic stress, this system begins to fail and cause ripple effects throughout the body. You may notice that in chronic stress, you begin to feel more tired and less mentally sharp, both indicators of a body that is struggling to keep up. Other symptoms may include insomnia, weight gain, poor digestion, poor immune function, suboptimal hormonal function, and mood concerns like anxiety and depression.


Knowing that the body’s top priority will always be our safety, we need to be consciously aware of the impact that stress can have on our whole system and make adjustments to how we perceive and manage our levels of stress. Luckily we do have the power to influence this default setting, and in this article, I’ll be reviewing a few ways to impact your levels of stress in order to support a healthier system overall and to improve your sleep.


1. Reflect on your stressors

Sit down in a quiet moment at the end of your day and allow yourself to rewind through your past day, week, month, and year. Jot down all of the mini stressors you experience on a daily basis. Then expand out to a macro level - what are the larger stressors that weigh on you. As the saying goes, knowing is half the battle.


2. Set a productive morning routine

The way you start your day influences not only your behaviour for the rest of the day, but also your physiology. Aim to create a window of normalcy in your day to help signal to the brain that everything is okay. The key requirement to this routine is a state of calm - the details of how you achieve this can vary. Perhaps this includes 5 minutes of meditation, prayer, or intention setting. It may include a slowly savoured cup of tea or coffee. Or maybe it includes listening to your favourite songs that help set the tone. You get to decide.


3. Create pauses for deep breathing throughout the day

A simple way to shift your physiology into PSNS land is through deep and slow breathing. Shallow and fast breathing signals stress and anxiety to your brain, whereas deep and slow breathing does the opposite. Bring your attention to your breath during stress to help calm you down, and try repeating this throughout the day to promote a calmer state of being.


4. Purge your mental stress nightly

Stream of Consciousness Journaling. An empty page in your notebook or an empty Word document - either works. Open the page, set a timer for 15-30 minutes, and start writing anything and everything that comes to your mind. The purpose is to free-flow, and not to structure these thoughts in any way. We often carry our thoughts from day to day and do not process or purge them. It is incredibly important to declutter the inside of your mind, and do so on a nightly basis to avoid these thoughts plaguing you overnight. If you haven’t yet used this strategy, it’s one that I highly recommend and urge you to put into practice for mental/emotional stress reduction, especially if you notice difficulties with sleep.


5. Move your body in ways that are fun and empowering

I’m sure you’ve heard the saying that our bodies are designed to move. Think through this concept and reflect on just how intentionally you are in supporting the physical capabilities your body has. Are you allowing the joints, muscles, and ligaments to do what they are designed to? Are you forcing your body to remain stagnant and stationary? Physical exercise and regular movement are two separate but equally important concepts. In order to reduce physical stress, it is important to build strength and deplete physical energy through exercise, while also supporting the health of our structures through daily movement. Start with 20-30 minutes of exercise, and incorporate walking throughout your day in between sedentary tasks.


6. Consider targeted supplementation and herbs when indicated

After supporting foundational health habits, it may be warranted to use targeted nutrients, herbs, or other supplements to improve the way your body handles the two systems: SNS and PSNS. We may consider some supplements to reduce the burden or build resilience to stress, and other supplements to improve your body’s ability to rest, digest, and sleep. Some of the commonly used therapies for managing sympathetic overdrive are adaptogenic herbs, B vitamins, vitamin C, and essential fatty acids like Omega 3 from fish oil. For supporting PSNS activity, we may use anxiolytic and nervine herbs, neurotransmitter modulators like GABA and Glycine, or calming supplements like melatonin, lavender, magnesium, or valerian root.


I hope this article helped you understand how connected the stress and sleep systems are, and the way they link to the workings of the Fight or Flight (SNS) and Rest and Digest (PSNS) systems.


If you would like support with determining which targeted supplements or interventions are best to support your body’s unique needs, book an appointment with me to discuss these options further.


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