The Stress Hormone Cortisol And Sleep

Last updated: December 5, 2019

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Cortisol has an impact on how you sleep, wake up, and even learn. It has many important roles in the body, but it seems that many of us with our hectic lives and not-so-good sleep schedules may have more cortisol than we should.

Too much cortisol is linked with anxiety and sleep disturbances. Bringing balance to your life and daily rhythm can help normalize your cortisol levels and offer you restful sleep.

What is cortisol?

Cortisol is best known for being a “stress hormone”, that is, it’s mainly released via the hypothalamic-pituitary-adrenal (HPA) axis as a response to stress. It also regulates blood sugar, aids in metabolism and is released daily as a part of our circadian rhythm

Cortisol and sleep – what’s healthy and what’s not

Being in line with circadian rhythm means that its levels fluctuate in a predictable pattern every day. Cortisol typically peaks early in the morning at about 9 am (or about 30 minutes after waking up) and it slowly decreases throughout the day and night. It drops to the lowest point at about midnight after which it rises again. 

Cortisol should not be elevated at night although prolonged stress can lead to high cortisol. Hyperactivity of the main stress response system (HPA axis) is associated with sleep disturbances, such as chronic insomnia. People with chronic insomnia have elevated cortisol in the evening and at their bedtime. 

Cortisol and sleep disturbances

High cortisol can shorten your sleep time and fragment your sleep, which means it’ll cause short sleep interruptions that you won’t even remember. Fragmented sleep means you have to go through light sleep stages much more frequently, leaving less time for deep, restorative sleep. Sleep fragmentation causes excessive daytime sleepiness (EDS) and all the problems that come with it.

Cortisol can be elevated at night even if you were sleep-deprived the night before. High cortisol is also found in people with obstructive sleep apnea (OSA).

Sleep problems can further bring imbalance to cortisol secretion which can throw you into a vicious cycle of elevated stress and sleep disturbances.

Waking up and cortisol – the cortisol awakening response

For the majority of people, cortisol levels increase sharply by about 50% within an hour of waking up, peaking about 30 minutes after waking. Some research suggests that the cortisol awakening response (CAR) is genetically set for each of us.

Some factors can increase cortisol in the morning even more. For example, waking up in the light causes a higher cortisol awakening response than waking up in the darkness as well as waking up earlier than usual. The cortisol response to awakening is higher on a working day than on a day off. 

Science is still looking for clear answers to why exactly most of us have the CAR but one suggestion says that it could be a way for our body to prepare us for the expected stress and high demands during the day.

The role of cortisol and sleep in memory and learning

Sleep plays an important role in our memory. During sleep, all the memories and knowledge we acquired while awake consolidate – that is, the information labeled as important gets strengthened and the “unimportant” memories weaken. Memories and emotions get connected and arranged while you enjoy your shuteye and cortisol can help you in the process.

A group of scientists wanted to see whether cortisol that’s present in the system at the time of learning affects memory. As it turned out, people who took some cortisol prior to learning and then went to sleep had much better chances of keeping those memories than those who didn’t take any cortisol. Cortisol seemed to “tag” memories, especially if they were related to emotions. This “tag” helped the brain retain those memories. 

High cortisol? Here’s how to lower it naturally

If you’ve been under a lot of stress and are dealing with poor sleep, you may want to think about managing the stress and lowering your cortisol levels. Here are some ways to do that:

  • Make your evenings relaxing. Don’t expose yourself to social media and gadget screens prior to your bedtime. Artificial light keeps you awake longer by suppressing melatonin, the sleep hormone, and social media is known to cause anxiety.
  • Don’t let the racing thoughts win. If you’re having problems with them, try breathing exercises and focus on muscle relaxation rather than giving in to your thoughts. They can just add to your stress.
  • Avoid alcohol and caffeine. Have a calming drink like chamomile or warm milk.
  • Do a hobby you love. Reading, writing, crafts, sports – it doesn’t matter – you need to vent.

Plenty of data tells us about certain things you can consume to lower your cortisol.

  • Make sure you have enough vitamin B5, B6, and vitamin C. 
  • For more support add calcium, magnesium, potassium, manganese, and zinc to your diet.

These nutrients are important because a stressed person is likely to lack them due to an overworked system.

  • Ashwagandha is widely recommended because it reduces cortisol and anxiety, improving mood and energy levels.
  • Magnolia also increases relaxation and helps in getting restful sleep. 
  • Phosphatidylserine lowers cortisol after physical stress.
  • Focus on GABA – the neurotransmitter that neutralizes stress. Foods and nutrients that help increase GABA are vitamin B6, magnesium, zinc, fermented foods (yogurt, kefir, kimchi), glutamine-rich foods (beef, chicken, cabbage), flavonoids (apples, tea, cocoa).

Another great way to relieve stress and increase GABA is exercise, especially when you also expose yourself to sunlight. Of course, this doesn’t mean excessively strenuous exercise – just the recommended amount for you. 

Additional resources

  1. Determinants of cortisol awakening responses to naps and nighttime sleep. https://www.sciencedirect.com/science/article/abs/pii/S0306453015009191?via%3Dihub
  2. Sleep and Cortisol Interact to Support Memory Consolidation. https://academic.oup.com/cercor/article/25/3/646/346948
  3. The Role of Cortisol in Sleep. https://www.naturalmedicinejournal.com/journal/2010-06/role-cortisol-sleep
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