What is REM sleep vs. deep sleep?

When in doubt, ask an expert.  Dr. Michael Breus, PhD, simplifies and differentiates REM sleep vs. deep sleep for us.

REM sleep = Mental restoration


Deep sleep = Physical restoration


REM sleep is imperative because of its mental restoration benefits.

Mental restoration is predominately related to:

#1 Memory consolidation

It serves as a shuttle bus moving data from your short-term memory to long-term memory.

#2 Emotional processing

So much impacts us emotionally in a single day, big and small.

REM sleep allows you to “emotionally process whatever emotional stressor is in your life.”

The most agonizing part can be reliving the same nightmare. Curious why that happens?

“When someone has a nightmare and they wake up, they stop the processing of that emotion until they go back to sleep again and they go to that point again.”

Breus said, “People with nightmares are often tortured because it keeps going on and on and on.” This is even more elevated for individuals with PTSD, as this is a primary symptom. The trouble is that PTSD clients “get a lot less REM sleep.”

Now let’s turn to deep sleep.

Two things happen during deep sleep leading to physical restoration:

#1 “The lymphatic system kicks into gear.” Breus refers to this as the “waste management system of the brain.”

Deep sleep is beneficial because it “scoops out all these proteins that start to build up over time (Beta-amyloid and Tao) and wrap around the nerves, which cause Alzheimer’s.”

# 2 “We get our largest bolus of growth hormone.” Breus likens it to taking your car into the body shop to get the dings, dents, and scratches out.

REM sleep and deep sleep are both critical to our health and well-being. So how do you know if you got REM sleep and / or deep sleep?

REM sleep is noted to start about 90 minutes into your sleep. “During a typical night, about 18 to 23% of sleep time is spent”* in this state.

Health conditions, medications and substances (alcohol/marijuana etc.) “can impact the length and quality of REM sleep.”*

When REM sleep is minimal, it “can affect their childhood development, learning, memory and even pain tolerance.”*

Deep sleep on the other hand is often what makes you feel refreshed the next morning, indicating you had a high-quality sleep. As you age, the time spent in deep sleep declines. Prior to that we spend about 10-20% of our sleep time in deep sleep.*

Now we have a better understanding of the difference between REM sleep and deep sleep – thanks to an expert in the field.

Dr. Michael Breus, PhD, is a clinical psychologist and both a diplomate of the American Board of Sleep Medicine and a fellow of the American Academy of Sleep Medicine.



This website does not provide medical advice. No material on this site is intended to be a substitute for professional medical advice, diagnosis or treatment. It is for informational purposes only.  Always seek the advice of a medical professional or other qualified health care provider on any health matter or question.


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