What causes a person to be nocturnal

What is sleep and why do we need it?

Although we spend about a third of our lives sleeping, science has yet to agree on why people sleep in the first place. Numerous studies have shown that sleep is essential for life and that it cannot be done without it. This is also the opinion of the American sleep researcher Allan Rechtschaffen: "If sleep does not have an absolutely vital function, then it is the greatest mistake that the evolutionary process has ever made." Because no other living being sleeps as deeply and soundly as humans. Although the body lies defenseless, as if paralyzed, in an unconscious state during sleep, the brain remains highly active.

Sleep Fact: Dolphins sleep with only one hemisphere of their brains, which they change every 1 - 2 hours as they appear during sleep to take a breath.

The fact that people sleep is characterized on the one hand by the natural day-night rhythm and their own internal biological clock. Flowers open their blossoms in the morning at sunrise, while bats retreat into dark caves and become active again at night. The natural enemies of humans such as saber-toothed tigers and lions were also usually diurnal mammals. It took a lot of energy to protect yourself from them. The nights were then used to hide from smaller nocturnal predators, to withdraw, to remain motionless and to shut down the body into an energy-saving mode. However, energy saving mode is not the main reason we overslept a third of our lives. Numerous functions have been demonstrated in sleep that are important for our survival.

How sleep works

  • Physical regeneration through the release of growth hormones
  • Breakdown of harmful, pathogenic substances
  • Processing of daily experiences (transfer of temporarily stored memories from the hippocampus to the long-term memory of the cerebrum)
  • Sorting out of nerve connections in the brain
  • Forgetting the unimportant
  • Consolidation and linking of what has been learned
  • Strengthening the immune system

The different phases of sleep

  • Physical regeneration through the release of growth hormones
  • Breakdown of harmful, pathogenic substances
  • Processing of daily experiences (transfer of temporarily stored memories from the hippocampus to the long-term memory of the cerebrum)
  • Sorting out of nerve connections in the brain
  • Forgetting the unimportant
  • Consolidation and linking of what has been learned
  • Strengthening the immune system

But not all sleep is the same. Sleep quality is less related to sleep duration than many might assume. While we sleep, our brain goes through five repetitive sleep phases that are of different length and depth. Sleep is not linear from falling asleep to dream sleep and then waking up again. Instead, the phases alternate in cycles. This also means that we wake up up to 28 times at night, but this is not remembered if the waking phase is shorter than three to five minutes.

Sleep phase

The sleep phase marks the first few minutes that we need to fall asleep. During this time the organism is shut down, calmed down and relaxed. The pulse slows down, breathing deepens, and the breathing rate decreases. Some people experience uncontrolled twitching during this time, which is a characteristic of muscular relaxation. Furthermore, a feeling of heaviness or a feeling of falling spreads, which can be perceived like a dream. In this phase, sleep is still very superficial, so that even small disturbances can interrupt falling asleep.

Light sleep phase

The light sleep phase is also called superficial sleep and begins immediately after falling asleep. The muscles are relaxed in this phase and the transition to the deeper, more restful sleep phases begins. We spend about half of the total sleep time in this phase, which is also important for processing the information we have received and for learning.

Light deep sleep

After the light sleep phase, the transition to light deep sleep begins, which leads to deep sleep. In the transition period to deep sleep, the body switches to energy-saving mode. The body temperature drops and the blood pressure decreases. In this phase there are no eye movements as in the dream phase. This is why this phase is also known as the Non-REM (Rapid Eye Movement) phase

Deep sleep

If the sleeper is now in deep sleep, it is very difficult for him to wake up. This phase is particularly important for relaxation. When we wake up in the morning and feel fresh and relaxed, it is because the deep sleep phases were particularly intense and long. At the beginning of the night, the sleep cycles have a high, longer proportion of deep sleep, so that the organism can recover even with little sleep. However, the number and length of the deep sleep phases continue to decrease over the course of the night. The first deep sleep phase is the longest and lasts around an hour. During deep sleep, the organism releases many growth hormones that promote the regeneration of body cells and strengthen our immune system.

Dream sleep phase / REM phase (Rapid Eye Movement)

Each deep sleep phase is replaced or interrupted by a dream sleep phase. The REM phase is characterized by the fact that the eyes roll back and forth wildly and twitch behind the closed lids. The brain activity is very similar to the waking state, since at this time the wildest dreams occupy the brain massively. When you wake up at this stage, you can remember the dream in great detail. Because the brain is very active in this phase and we experience all kinds of adventures in our dreams, the brain stem paralyzes the muscles so that we do not act out what we have dreamed of and do not injure ourselves. Limbs can still twitch, however, which means that you can get a kick or kick from your bed partner. If you wake up during a nightmare in this phase, the body remains paralyzed, which can certainly lead to anxiety.

The sleeper goes through this alternation between deep and dream sleep about four to six times a night. In the last third of sleep, the body gradually prepares to wake up again and begins to release large amounts of the hormone cortisol, which is supposed to wake us up again. In the last hour before waking up, you slide into a light twilight sleep, which is similar to the light sleep phase after falling asleep.

Sleep phases and cycles change with age. The deep sleep phases become shorter and remain more superficial. Instead, the number of short naps during the day increases and ensures relaxation.


How much sleep do you need?

A large-scale, one-year study with 10,000 participants has shown that the optimal night's sleep lasts between 7 and 8 hours. Cognitive tests were also taken, in which the participants who previously slept for less than four hours did the worst.

But how meaningful are the results of this study really? Albert Einstein is said to have slept for 12 hours, while former Apple boss Steve Jobs only slept four hours a night. How many hours is it then, the optimal sleep duration?

First of all, it is important to find out whether you are a short or late sleeper yourself. Only then can you determine the time you need for a good night's sleep.

A distinction is made between:

Short sleepers

Medium sleeper

Late riser

So the question shouldn't be: How much sleep do you need? But: how much sleep I needI?


Negative consequences of lack of sleep?

First of all, it is important to distinguish between the duration of sleep and the quality of sleep. It is possible to have a short but good sleep as well as long and bad sleep, because everyone reacts differently to lack of sleep. Most people, however, show cognitive impairments after just one bad night and experience serious losses after several bad nights that are comparable to a blood alcohol level of 0.6 per mille. Particularly critical here: People who suffer from chronic lack of sleep perceive themselves to be more productive than they really are.

In contrast, around a third of all people are relatively insensitive to lack of sleep. Nonetheless, there are a few general effects associated with poor sleep:

  • Impairment of physical and mental performance
  • Memory problems
  • Restlessness
  • irritability
  • Mood swings
  • Increased risk of accidents at work and in traffic
  • Microsleep
  • Dejection
  • exhaustion
  • high blood pressure
  • Obesity
  • Metabolic disorders
  • diabetes
  • Heart disease
  • weakened immune system and higher risk of disease
  • Increase the likelihood of a mental disorder
  • Increase the likelihood of developing cancer


What are sleep disorders and how do they arise?

Sleep disorders are divided into the three categories of difficulty falling asleep, difficulty sleeping through the night and premature awakening. The overarching commonality of these categories is the lack of restful sleep. As a result, those affected feel more tired during the day and have difficulty falling asleep and staying asleep. If the symptoms occur continuously for at least a month on three days a week, one can speak of disturbed sleep behavior or a sleep disorder. Statistically speaking, sleep disorders are one of the most common health complaints in Germany.

The causes for the development of sleep disorders can be of different nature for each individual. Sleep disorders can arise from external influences such as noise, light, medication or drugs, learned behavior or physical or organic triggers. Organic triggers can be genetic or related to mental disorders that promote the development of the sleep disorder.


What sleep disorders are there?


Sleep deficits, which are characterized by nocturnal insomnia, such as difficulty falling asleep, staying asleep and waking up prematurely, are medically referred to as insomnia.

Factors that favor insomnia include:

  • Stress (work-related or private)
  • caffeine
  • alcohol
  • Drugs
  • Medicines (antibiotics, blood pressure drugs, and asthma drugs)
  • Physical illnesses (colds, strokes, dementia, chronic pain)
  • Mental illnesses (depression, anxiety disorders)
  • shift work
  • Genetic predisposition
  • Personality traits
  • Nap
  • Excessive brooding and worrying

Affected people lie in bed in the evening and torment themselves with thoughts like "I have to finally fall asleep now because otherwise I will not be fit tomorrow." During the day they do not feel rested and are already worried about the coming night, in which they will most likely also not be able to sleep. This vicious cycle consolidates the sleep disorder.

Insomnias are divided into three degrees of severity, mild, moderate, and severe, based on the frequency and intensity of the symptoms.

With regard to the persistent duration, insomnias are divided into acute (up to four weeks), subacute (up to six months) and chronic (longer than six months). In addition to its cause and severity, the duration of the insomnia is also decisive for the appropriate choice of therapy.


Hypersomnia describes a permanently increased need for sleep and excessive daytime sleepiness. The excessive need for sleep during the day is the most widespread one in the category of sleep medicine diseases, but is taken the least seriously. Those affected describe their sleep as positive because they achieve a satisfactory sleep time and do not perceive this as an obvious impairment. Instead, they experience their hypersomnia as general tiredness, which they try to resolve with their own coping strategies (caffeine consumption, afternoon nap). Most of those affected do not realize that this perceived, permanent tiredness is a hypersomnia. Studies have shown that the cause of hypersomnia lies in a nightly disturbance of sleep, which, however, goes unnoticed by the sufferer. These include breathing and movement disorders such as snoring or twitching.

Hypersomnias are also divided into three degrees of severity, mild, moderate, and severe, based on the frequency and intensity of the symptoms. The more severe the hypersomnia, the more difficult it is for people to resist falling asleep uncontrollably during the day.


Parasomnias (Greek “para” = next to it) denote physical or autonomous (uncontrollable) events such as sleepwalking, turning around, talking, screaming or bruxism (grinding teeth) that result from sleep but have no direct effect on it. Parasomnias have no negative influence on the perceived quality of sleep and do not directly influence it. However, they can pose dangers for the sleeper himself, bed partner or others.

This sleep disorder can also arise from the use and abuse of medication or occur as a result of mental or physical illness. In this case, they are called symptomatic parasomnias.

Sleep-wake rhythm disorders

Sleep-wake rhythm disturbances occur when one's own internal clock differs from the natural day-night rhythm. This can result from internal causes such as brain damage from inflammation, stroke, Alzheimer's disease or head injuries as well as general insensitivity. External causes such as jet lag, shift work, irregular bedtime, medication or being confined to bed can also lead to a rhythm disturbance. In this case, one's own biological clock is in a different rhythm, so that one is tired even though it is day or one is awake at night. Affected people cannot wake up or fall asleep when they want to and also fall asleep at inconvenient times without being able to control it.


What can you do about insomnia?

In the following, we would like to introduce a few strategies that can prevent sleep disorders, but which are also helpful if you already suffer from mild sleep disorders.

Sleep hygiene

Basically there are a few classic rules for good sleep, which are summarized in psychology under the term “sleep hygiene”. Just like with classic hygiene, you should follow rules such as thorough hand washing to protect your health, you can also follow some sleep hygiene rules that contribute to a good night's sleep.

General sleep hygiene tips

Good sleep starts with a healthy lifestyle. Regular exercise or other physical activity has a positive effect on sleep because it exhausts the body and thus increases sleep pressure. You should only refrain from high-performance sport shortly before going to sleep, as it activates the body and stress hormones. This rule can be applied to any kind of intense physical and mental exertion. In these phases of performance, the body activates all important body systems and then needs a certain amount of time to shut down again. Therefore, starting around 2 or 3 hours before going to bed, you should gradually reduce strenuous activities. This can be made possible by introducing a personal sleep ritual.

Incidentally, sexual activity does not count as high-performance sport and is generally viewed as promoting sleep because it activates the parasympathetic nerve - the rest nerve in our body.

However, sleep hygiene is not just about adding helpful activities, but also reducing things that have a negative impact on sleep. So from after lunch you should refrain from caffeinated drinks such as coffee, black tea or cola and also limit the consumption of alcohol and never use it as a sleep aid. Alcohol consumption can help you fall asleep faster, but it causes our sleep quality to suffer and we wake up more often at night. In order not to overload the body with its own digestion, one should also avoid heavy meals before sleep. 

There are also some sleep hygiene rules in the bedroom that lead to better sleep. So it is important to create a pleasant atmosphere that invites you to sleep. On the one hand, this includes setting a comfortable room temperature. You should also make sure to create a spatial separation between the work and sleeping areas. Bright light in the evening (e.g. from cell phone or computer screens) should be avoided. However, light - especially natural daylight - is helpful for waking up in the morning.

The bed is there to sleep

The so-called “stimulus control” plays a special role in sleep hygiene. The aim behind this is to (re) connect the bed with its original function of sleeping. Stimulus control therefore includes refraining from activities in bed that are not asleep. Watching TV, working, eating or the like should only be done outside of bed. The exceptions to this are sexual activities and reading has a special role if it causes drowsiness.

If you wake up at night and lie awake for a long time, get out of bed and do some pleasant and calming activity instead. For example, you can listen to music or read in the living room until you are tired enough to go to bed and fall asleep. The bed should only be used for sleeping and only be used when you are very tired.

Regular sleep-wake rhythm

Another part of sleep hygiene is related to the regularity of your sleep. Because the more even the sleep rhythm, the easier it is for the body to get tired at the right time. To achieve this, it is important to get up at the same time in the morning, regardless of how long you slept. If possible, this rhythm should also be adhered to on the weekend to make it easier for the body to adjust to a regular sleep pattern.

SLEEP FACT: When traveling long distances across different time zones, our sleep-wake rhythm shifts very quickly and we experience what is known as “jet lag”. For each time zone crossed, it takes about one to two days for the body to get used to the new rhythm.

Sleep tracker apps and devices

Many people who are interested in their sleep have already come into contact with apps or devices that advertise that they can measure and evaluate sleep. These technical aids can provide interesting insights and be a good introduction to dealing with your own sleep behavior.

When using these devices and apps, however, one should be aware that the results are not as precise as those of sleep tests in a sleep laboratory. According to a current scientific study, the devices often assess sleep as too long and can usually not correctly reveal the extent of sleep disorders. For this reason, it is important not to stop paying attention to your own feelings. Most of the time, you know best yourself how restful your sleep really was last night.


Relax and switch off to fall asleep

Following the rules of good sleep hygiene can help prevent poor sleep. But sometimes you lie awake at night despite these rules and have difficulty switching off. It can be useful to have a few strategies on hand to help you get into sleep mode.

Relaxation techniques

As the name suggests, relaxation techniques can be very helpful to help you fall asleep more easily in the evening. One of the most effective relaxation techniques is the so-called “Progressive Muscle Relaxation” (PMR). This is a structured relaxation training in which different muscle groups are tensed and relaxed again one after the other. For best results, PMR should initially be performed under the guidance of an experienced therapist. After a certain learning and practice time, exercises can then also achieve their full effectiveness on their own.

Professional training instructions for PMR practice are offered in many academies, adult education centers and health insurance companies. Alternatively, you can learn the PMR practice from a psychological psychotherapist or as part of our HelloBetter sleep training.

Quiet image and imaginary journeys

Another technique to better switch off before going to sleep are pictures of stillness and imaginary journeys. The attempt is made to draw attention to positive thoughts in order to get out of the cycle of negative thoughts.

With the idle picture, you call up a concrete, pleasant, calm memory (for example a scene from your vacation). The resting image should not contain any other people or hectic, fast activities. The aim is to imagine everything as concretely and in as much detail as possible and to immerse yourself in this imagination: What can you see, hear or feel? Is there a specific smell or taste? How is the weather in the situation?

Based on the calm image, the situation can also be turned into a so-called fantasy journey. So if you sit in your mind in a beach chair on vacation, for example, the idea of ​​a walk on the beach can be developed.


The practice of mindfulness is a traditional method from Buddhism. The aim of mindfulness is not primarily to relax, but to direct one's attention to the current moment and to perceive all sensory impressions and thoughts without judgment.

But this mindfulness practice can be very helpful, especially for people who have difficulty switching off in the evening. If you manage to focus your attention on the present, you can't get lost in brooding over a problem in the future or the past. In addition, practicing an accepting attitude towards one's own experiences can be useful, for example to reduce the pressure of having to fall asleep.

There are many different mindfulness exercises, e.g. classic sitting meditations in which you focus your attention on your breath. As soon as one strays from the breath and chases after thoughts, one should try to merely register them and then bring the attention back to the breath. Alternatively, one can also integrate mindfulness practice into everyday life and look carefully at every step while walking or other everyday experiences.

Sleep fact: In scientific studies it has been found that experienced meditators who meditate for several hours a day have a lower need for sleep than comparable persons who do not meditate.

Dealing with sleeping pills and medication

One drug that many people who suffer from insomnia and long for better sleep resort to is sleep medication. In a critical phase of life, such as after the death of a loved one or before a frightening operation, it can be entirely justifiable to take a sleeping pill for a limited time in order not to experience any further impairments due to poor sleep in this stressful situation.

However, as soon as the personal intake of sleeping pills continues for more than 2 or 3 weeks, self-medication should be viewed critically. The reasons for this lie in the inherent side effects, the high risk of addiction and the risk that in particular the rapid withdrawal from sleeping pills can have drastic consequences. For this reason, we recommend that you only take sleeping pills in close consultation with your doctor and slowly taper off exactly as instructed.


How long will it take before I can sleep properly again?

The techniques presented can be very helpful in counteracting mild insomnia, but sometimes they are not enough to get you consistently better sleep again. It can be quite normal to have poor sleep for a few days or weeks, if the living conditions contribute to it. However, if you experience sleep problems and / or a high level of suffering over a long period of time, it can make sense to get support from experts. As part of our HelloBetter training, you can also get to know scientifically sound and effective cognitive-behavioral therapeutic techniques in order to sleep better.


Sleep better now with HelloBetter

Poor sleep and sleep disorders are stressful and can seriously affect the quality of life. That's why we've developed scientifically based sleep training that can help you cope with your sleep problems.

The training is suitable for anyone who regularly has problems falling or staying asleep and wants to use effective techniques to change this. These include:

  • Techniques that will help you break down bad sleep habits and establish better sleep routines.
  • The use of a sleep diary and the tried and tested method of sleep restriction
  • Techniques for dealing with critical thoughts, worries, and problems
  • Learning strategies that will help you to actively relax in everyday life.

By the way, we are currently looking for participants for our scientific sleep study GET Sleep. If you suffer from difficulty falling asleep and staying asleep and want to cope with your sleep problems, then register for free on ▷ GET Sleep.de. With your participation you not only make an important contribution to sleep research, but you can also use our new online sleep training free of charge.