Cortisol Wake Response: Stress and Sleep

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No one—unless you’ve cracked some sort of superhuman code—maintains the same levels of energy throughout the day. But our ebbs and flows are largely genetic and determined by the internal sleep-wake cycle known as your circadian rhythm.

This daily pattern lasts roughly 24 hours and is regulated by the rise and fall of certain hormones, including cortisol. Cortisol is your body’s main stress hormone, and it may play a crucial role in how energized you feel first thing in the morning.

What is the Cortisol Wake Response (Cortisol Awakening Response)

The cortisol awakening response, or CAR, refers to a sharp increase in cortisol that happens within the first hour after waking up. This 38 to 75 percent spike in cortisol is generally highest between 30 and 45 minutes after waking.

Normally, the biggest cortisol spike happens during the second half of the night when you’re fast asleep. Since CAR seems to be independent of that spike, some scientists have theorized that it’s the result of anticipating “demands of the upcoming day (stress anticipation) and could support coping with daily life stress.” So, in a sense, it’s like a shot of espresso for the brain—a way to help you face the day ahead.

It’s important to note that not everyone experiences CAR and it may come with downsides. Some research links larger early morning cortisol spikes to future clinical depression and an increased risk of cardiovascular diseases.

Cortisol and Stress

Cortisol is often referred to as the “stress hormone” because it’s involved in the fight-or-flight response. When you’re under stress, your adrenal glands release adrenaline and cortisol into your bloodstream to give you the energy and strength you need to deal with the perceived threat.

But chronic stress can lead to high cortisol levels that stay elevated long after the initial threat has passed. This can lead to health problems, including:

  • Headaches
  • Memory impairment
  • Concentration impairment
  • Digestive issues
  • Weight gain
  • Muscle tension
  • Muscle pain
  • High blood pressure
  • Anxiety
  • Depression
  • Heart disease
  • Heart attack
  • Stroke

While scientists are still working to understand the role CAR plays in overall health, managing your stress levels and getting enough sleep to maintain a healthy balance of cortisol in the body are both beneficial. Normal ranges of cortisol vary throughout the day, but generally, they are:

  • 6-8 a.m.: 10 to 20 micrograms per deciliter (mcg/dL)
  • 4 p.m.: 3 to 10 mcg/dL

Some studies have found that on more demanding days, CAR levels are higher. However, researchers are still learning the best ways to measure this morning cortisol spike and its effects on health.

To reduce your stress levels and keep your cortisol in check, try engaging in some mindfulness activities like gentle yoga, meditation, or deep breathing exercises. You can’t eliminate stress completely, but making a conscious effort to minimize the major stressors in your life can have a big impact on your health.

Cortisol and Sleep

Cortisol plays an important role in your sleep-wake cycle. Levels are highest in the morning and fall throughout the day, hitting their lowest point around midnight. Most people will also experience around 15 to 22 smaller pulses of cortisol throughout the day.

This natural rise and fall of cortisol may help regulate your internal clock and make you feel sleepy and alert at the appropriate times. Cortisol levels also increase in response to stress, which is why you may have trouble falling asleep when you’re anxious or under pressure.

Cortisol is produced by what’s called your hypothalamic pituitary adrenal (HPA) axis. And studies show that an overactive HPA axis can seriously mess with your sleep cycles, resulting in:

  • Fewer hours of sleep
  • Fragmented sleep
  • Insomnia

This, in turn, has a ripple effect on how—and when—your body produces cortisol. For example, a few studies have reported that sleep conditions like sleep deprivation and insomnia can actually trigger your body to produce more cortisol.

While the relationship between cortisol and sleep is still being explored, it’s clear that getting enough quality shut-eye is crucial for maintaining a healthy balance of the stress hormone.

To keep your cortisol levels in check, aim for 7 to 8 hours of sleep each night. You should also avoid working late into the evening or staring at screens right before bed. If you have trouble sleeping, talk to your doctor about possible treatment options.

What Factors Affect Cortisol Levels?

Cortisol doesn’t spike or drop randomly. There’s almost always a reason behind it. Here are some of the most common causes.

  • Poor diet: A diet high in refined sugars, salt, fat, and animal proteins can impact the circadian production of cortisol.
  • Stress: Cortisol is released in response to stress, both physical and psychological, but usually, the spike is temporary. When repeated stressors lead to persistently high cortisol, it can disrupt many of the body’s processes.
  • Trauma: Studies have found that people who experienced traumatic events can have irregular cortisol levels for years afterward. Both high and low cortisol levels have been found in survivors, leading researchers to believe that their stress responses may have adapted to their environment.
  • Sleep disorders: Sleep apnea obstructs your breathing while you sleep, resulting in fragmented sleep and higher cortisol levels.
  • Cushing’s syndrome: This rare disorder occurs when your body is exposed to high levels of the hormone cortisol for a long period of time. It is usually caused by a long-term, high dosage of corticosteroid medications.
  • Cushing’s disease: Unlike Cushing’s syndrome, Cushing’s disease is not caused by medication. It’s the result of a tumor on the pituitary gland that leads to high cortisol levels.
  • Addison’s disease: This rare disorder is caused by damage to the adrenal glands, resulting in cortisol deficiency. It can be caused by an infection, an autoimmune condition, or cancer.


Your body is an amazing, intuitive machine that’s capable of adapting and responding to the environment around you. The cortisol awakening response can help you wake up in the morning, but having consistently high cortisol levels may lead to complications.

Taking care of your body by eating a nutritious diet, getting enough sleep, and managing stress can help keep cortisol levels in check. And if you think you may have a hormone imbalance, talk to your doctor. They can help you get to the root of the problem and find a treatment plan that works for you.

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