Why Do We Sleep At Night? Theories of Sleep Explained


🌙 Written by Kai Riverstone, international lucid dreaming expert and teacher. Learn how to lucid dream in 7 days or less.

Scientists estimate that we spend approximately 33% of our life asleep. Yes, 33%! That’s a lot of time spent getting our ZZZs in… but have you ever stopped to wonder WHY we spend so much of our lives asleep?

By the way, 33% of our lives is a LONG time, so wouldn’t it make sense to spend that time experiencing incredible things and living out our fantasies, WHILE you’re asleep? You’re gonna spend the time doing nothing anyway.. Learn to lucid dream! Anyway, on with the post…

If we need so much sleep then why does western culture seem to place such a strong emphasis on being super busy and productive? And while we’re on the subject, what exactly is sleep and how do we adequately define sleep and everything that the process entails?

What is Sleep?

Loosely speaking, sleep is defined as the rest and relaxation of the mind and body, characterised by the absence of conscious thought and movement.

When we sleep contact between the brain and the external world is lost and many spiritual seekers believe that when this happens we descend closer to our own inner power/consciousness.

Despite the rapid advancements of modern technology and the fact that sleep is the most basic and natural thing in the world, theories on why we sleep are still shrouded in mystery.

In fact, it wasn’t until the early 20th century that scientists started conducting tests to find out more about sleep and sleep cycles.

What is a Sleep Cycle?

Until relatively recently, primitive man assumed that the mind switched off during sleep and that dreams were the result of some mysterious, otherworldly phenomena that defied any rational explanation.

Despite this or rather, in spite of this, primitive man held dreams in extremely high regard. From the Aboriginals of Australia to the Ancient Greeks and Romans, the night world of dreams held a special place in the spiritual evolution of mankind.

When scientists started delving deeper into the world of sleep, they discovered that the brain doesn’t just switch off while we sleep but is in fact, highly active.

More tests and experiments revealed that sleep has two phases:

  • REM Sleep (Rapid Eye Movement)
  • Non-Rapid Eye Movement Cycle NREM sleep or Slow Wave Sleep

What is the Difference between each Sleep Cycle?

We go from NREM to REM cycle several times in one night (approximately 5 cycles if we are getting 8 hours of sleep a night). 5 cycles seems to be the ideal time, where MORE than that or LESS than that leaves us feeling tired or lethargic. 

A complete cycle (meaning a NREM-REM cycle) lasts anywhere from 90 to 110 minutes, however, NREM cycles decrease and REM cycles increase as the night goes on. This is why the best time to lucid dream is early morning when your REM cycles are at their longest. 

The NREM Phase

The NREM sleep cycle is characterised by marked physical and physiological changes that prepare you for going into a deep sleep.

It can be broken up into four main stages.

  • Stage 1: At this stage you are just drifting off to sleep. Because you have not yet reached the deepest stage of sleep, you can easily be wakened by ambient noise. Have you ever been drifting off when you suddenly feel like you are falling? This happens in stage 1 of the NREM sleep cycle.
  • Stage 2: At this stage, your body prepares itself for deep sleep. Your body temperature and heart rate drop. You are now sleeping lightly, as you would if you were taking a “cat nap.”
  • Stage 3: Stage 3 is when deep sleep takes hold. It is hard to wake someone up who is in stage 3. This is a deep, dreamless sleep that strengthens your immune system and allows your bones and tissues to do some vital repair work.
  • Stage 4: This is the deepest sleep there is. You do not dream during this stage and your body continues with its repair work.

The REM Phase

The REM cycle occurs roughly 70-90 minutes after you fall asleep. During the REM sleep cycle your eyes dart about quickly beneath your closed eyelids, hence the name; ‘Rapid eye movements’ or REM.

When you are in REM sleep your pulse rate quickens, your brain activity increases and you have vivid dreams (even though you may not remember them). Each REM cycle lasts approximately 10 minutes and increases to as much as one hour in the final hours before you wake up. This is why we tend to have our most vivid dreams in the morning.

The physical and mental health benefits of sleep

While you get your much-needed sleep, your body is able to repair itself. Each phase of sleep is beneficial to your mental and physical well-being. While REM sleep produces dreams and promotes learning, NREM sleep repairs your tissues and bones and strengthens your immune system.

Each distinct phase of the sleep cycle has its own unique health benefits and works as part of a holistic cycle, meaning the interplay between NREM and REM sleep is just as important as each distinct phase.

After being active all day our bodies and minds need time to shut off from external stimuli. While NREM sleep repairs our bodies, REM sleep helps us to release the buildup of psychic tension from the subconscious. It also helps to awaken our deeper, unconscious instincts and drives.

Why do we sleep at night and not during the day?

Our sleep cycles are governed by the circadian clock. Think of your circadian clock as an in-built timekeeping device that regulates body temperature and releases neurotransmitters (special chemicals) into the bloodstream.

For example, when nighttime rolls around, your brain naturally releases a chemical called adenosine into the bloodstream. This is what is responsible for making your feel sleepy as well as giving you a drop in body temperature.

In the morning your circadian clock releases another stream of neurotransmitters, signalling to your body that it is time to wake up. This is why many people report waking up at the same time every morning no matter how early/late they go to bed.

The Spiritual reason we sleep

Besides the mental and physical benefits of getting quality shuteye every night, sleep is also one of the most profound evolutionary tools given to us as human beings.

It is not a coincidence that cultures the world over believed that being in touch with the dream world could help us access higher schools of learning. This means that ignoring our dreams and devaluing the benefits of sleep is like missing out on one third of our lives and thus, a third of our potential.

The idea that higher learning takes place while we are in REM sleep is now being backed by science.

This means that those who take an active interest in modalities such as lucid dreaming, Jungian dream analysis and yoga nidra are actually assisting in their spiritual development.

Sleep theories

From psychoanalysis and Yogic scriptures, to Koranic verses and Buddhism, it is believed that sleep brings us into contact with the deepest layers of the psyche so that they can be assimilated into conscious expression.

Every experience and impression that we come across in our lives is registered in the subconscious mind and so working with our dreams can help bring these stored impressions to waking consciousness. This means that dreams give us the ability to rid ourselves of self-limiting beliefs and programs that hinder our growth.

What happens if we DON’T sleep?

If you don’t sleep or stop going to sleep at night, bad things start to happen. After just 48 hours you feel tired, drowsy, ill, sick and even start hallucinating. After 72 hours or more of no sleep you start vividly hallucinating, and you can even die if you go for long periods of time without sleeping.

Why do we sleep after eating?

It’s very common to want to sleep or feel very tied instantly after eating. The reason for that is the sugar in the food you’re eating. Not ALL food makes you feel tired after by the way, it’s just foods that are high in natural or unnatural sugars, which cause your body to secrete a high amount of insulin to counteract it.

You wouldn’t feel so tired after each meal if you ate a vegan or plant based diet (or even just a low sugar diet, and ate some sort of fats or proteins WITH carbs at each meal). 


Dreams ultimately lead to self-realisation while deep, dreamless sleep lessens the harmful effects of the flight or fight response by regulating adrenaline levels and stress hormones and normalising blood pressure.

Sleep is thought to be directly linked to our evolution on a biological level (for example, animals lower down on the food chain need more sleep) as well as on mental and spiritual levels, too. This means that the simple task of going to bed every night gives you the power to unlock your greatest potentials and abilities so that you can live your best life possible.

Take it beyond sleep

Sleep is of course very important to us as humans, but what comes next? With lucid dreaming you can take control of that extra third of your life, and USE it to achieve incredible things. You can fly across mountains, and become a superhero.

  • Get started with lucid dreaming by being one of the thousands of lucid dreaming bootcamp students who are hacking their dreams and controlling them easily!
  • Try a sleep aid supplement like this or listen to relaxing binaural beats that are proven to help you fall asleep faster, and have more lucid dreams
  • Use a meditation machine like the Proteus to relax and meditate deeply