According to the Centers for Disease Control and Prevention (CDC), 35.2% of adults in the United States are getting less than 7 hours of sleep each night. It is recommended that adults get 7-9 hours of sleep a day, so that’s a staggering fraction of the population walking around sleep-deprived in their day-to-day lives; this is mostly due to longer working hours and round-the-clock entertainment available at our fingertips.

After exploring the physiology of the stress response and whether there is any such thing as an “ideal amount” of stress, we set out to answer a few slumber-related questions in this one.

What is the function of sleep?

We spend about a third of our lives sleeping, and it has a critical role to play in our health.

Besides giving your body and mind some much-needed rest, a healthy amount of sleep is vital for “brain plasticity,” or the brain’s ability to adapt to input(1). With inadequate sleep, we are not able to process properly what we have learned and also face more trouble remembering it. Sleep may also be responsible for consolidating new memories, and helping you forget the unimportant parts of your day, making ‘space’ for new learning the next day(2). Researchers also believe that sleep may promote the removal of toxins from brain cells—which seems to occur less efficiently when the brain is awake.

“It turns out that sleep is a period during which the brain is engaged in a number of activities necessary to life — which are closely linked to quality of life,” says Johns Hopkins sleep expert and neurologist Mark Wu, M.D., Ph.D. 

So what does sleep have to do with stress, or the elevated cortisol levels that come with it? 

Are cortisol levels affected by sleep?

Your cortisol levels start to rise about an hour before you wake up, and, shortly after waking up, a sharp 38–75% (average 50%)(3) increase occurs in the blood level of cortisol in about 77% of healthy people of all ages. This is likely because your body is preparing itself for the anticipated stressors of the day. Read more about the cortisol awakening response here

Cortisol also inhibits the secretion of hormones like melatonin and others, which modulate the sleep–wake cycle, while their dysfunction can disrupt sleep. In turn, sleep loss influences the Hypothalamus-Pituitary-Adrenal axis, or the HPA axis, leading to hyperactivation(4).

You might have noticed difficulties in learning and memory when you’re sleep-deprived – this is because the hippocampus(5) in the brain, which controls these abilities, is super sensitive to cortisol. If your glucocorticoid levels are very high (due to factors like lack of sleep) – you won’t be able to consolidate information as effectively when you are sleep-deprived. 

What is the effect of deep sleep on stress and anxiety?

Elevated cortisol levels lead to less delta-wave sleep or deep sleep; researchers have found that the type of sleep most apt to calm and reset the anxious brain is deep sleep, a state in which neural oscillations become highly synchronised, and heart rates and blood pressure drop(6)

“We have identified a new function of deep sleep, one that decreases anxiety overnight by reorganising connections in the brain,” said study senior author Matthew Walker, a UC Berkeley professor of neuroscience and psychology. “Deep sleep seems to be a natural anxiolytic (anxiety inhibitor), so long as we get it each and every night.”

Simply put-

The next time you’re feeling overwhelmed with an issue, consider calling it a day and tackling the problem again after a good night’s rest. There’s a reason ‘sleeping on it’ has become such popular advice to destress!

What happens when you are sleep-deprived?

If you’ve been facing a lot of stress at work recently and have been struggling to get enough shut-eye, you might have to deal with trouble concentrating, low energy, a negative mood and an overall inability to function as you normally do.

Chronic sleep deprivation, however, can increase the risk of several chronic health conditions, with a report by the Centers for Disease Control and Prevention (CDC) stating that people who get less than seven hours of sleep per night face an increased risk of developing:

  • obesity
  • heart disease
  • diabetes
  • stroke
  • depression
  • arthritis
  • kidney disease

There is data supporting the view that insufficient sleep, by acting on stress systems, may sensitise individuals to stress-related disorders(7). In fact, epidemiological studies suggest that sleep complaints and sleep restriction may be important risk factors for a variety of diseases that are often linked to stress, including cardiovascular diseases and mood disorders.

Studies have also shown as association between sleep duration and obesity(8), both in children and adults, suggesting that shorter sleep durations may be able to predict weight gain and even lead to decreased insulin sensitivity(9) (indicating a risk factor for insulin resistance). You can read more about the relationship between stress, sleep and metabolism here.

In the end, besides getting enough sleep, other lifestyle choices such yoga and meditation, regular physical exercise and better food habits too can contribute towards stress relief and a healthier life in which stress can be effectively managed.