How do we understand sleep?

Sleep is an essential biological process that all people and many animals experience, marked by a reduction of physical activity and a decrease in reactions to external stimuli.

From the point of view of neuroscience, sleep is a complex process involving various brain areas and neurotransmitter systems, which regulate the transition between waking and sleeping and control the different sleep phases.

The sleep-wake cycle is regulated by circadian rhythms (24-hour rhythms), driven by the suprachiasmatic nucleus in the hypothalamus: our internal clock. This internal clock reacts to external light signals and regulates the production of melatonin, a hormone that promotes sleep, by the pineal gland.

Non-REM and REM sleep

Sleep consists of several cycles of non-REM and REM (rapid eye movement) sleep. Each cycle lasts about 90 minutes and repeats several times a night.

Non-REM sleep is divided into three phases, from light sleep (phase 1) to deep, restorative sleep (phase 3). During these phases brain activity decreases, with the exception of deep, slow brain waves, the so-called delta waves of phase 3.

REM sleep is marked by rapid eye movements, raised brain activity that resembles the waking state, and vivid dreams. During REM sleep the muscles are almost completely relaxed, possibly to prevent us from acting out our dreams.

Various neurotransmitters play a part in the sleep-wake cycle, including serotonin, norepinephrine, acetylcholine, GABA (gamma-aminobutyric acid) and hypocretin.

The experience of sleep

The subjective experience of sleep can vary a great deal. During non-REM sleep people can be in deep rest, with strongly reduced awareness of the outside world and of their own thoughts. During REM sleep people often have vivid dreams, although they do not always remember them on waking.

The restorative aspects of sleep, such as recovery of energy, strengthening of the immune system and the consolidation of memory and learning, take place mainly during the deep phases of sleep. A good night’s rest is associated with a range of positive health outcomes, including better cognitive functioning, emotional regulation and general physical health.

Factors that influence sleep

Our sleep cannot simply be regulated ‘from above’, because it is closely tied to our whole life: its regularity, the events in it, the level of stress and even the structure of our existence.

Food

An important aspect is what we eat. Sleep can be negatively affected by a diet rich in fats, salt and sugars, which is all too common in our society. So common that it is no longer seen as a problem.

The use of alcohol and of stimulating substances such as coffee, tea, cannabis, MDMA, methylphenidate, amphetamine and cocaine can also have an enormous impact on sleep. Irregularities in the sleep pattern, such as going out late, strengthen this effect.

Mental distress

Mental distress, filled with circling, compelling emotions, anxiety above all, also contributes to sleep problems. This can show itself in worrying, a negative view of the future, or hearing voices that disturb sleep.

Medication

The use of psychiatric medication can also disturb sleep, directly or through withdrawal symptoms, paradoxical reactions or side effects such as restlessness in movement.

Sleeping pills are not medicines for sleep

Because of this multitude of factors our sleep is easily disturbed. A good night’s rest requires a regulated and perhaps even somewhat ‘boring’ life. But a boring, predictable existence is granted to us less and less. Many people therefore reach for sleeping pills as a solution to their sleep problems, but this is a complicated and often problematic step. Sleeping pills, in the strict sense of the word, do not really exist.

Benzodiazepines

There are medicines that cause sedation, which makes sleeping easier. The most used are benzodiazepines, such as temazepam and lorazepam. These medicines act on the GABA system in the brain, the same system that alcohol acts on, and can help with falling asleep. Zolpidem and zopiclone are related to benzodiazepines (the so-called Z-drugs), with the same potential for tolerance and addiction.

When benzodiazepines or Z-drugs are used for longer than one or two weeks, tolerance and habituation develop, so that the medicine becomes less effective and the need for higher doses grows. Addiction also develops easily: no longer being able to do without the medicine.

Antidepressants, antipsychotics or another medicine

Some people therefore try antidepressants, antipsychotics or another medicine with sedative properties as an alternative.

• Trazodone, an antidepressant with sedative properties, is sometimes used to help with falling asleep.
• Quetiapine, an antipsychotic, is also often used as a sleeping pill, in a low dose of 25 mg.
• People also sometimes use promethazine, an antihistamine that is sedative too, to help with falling asleep.

The problem is that these medicines are not officially registered as sleeping pills, can have considerable side effects and are not meant for long-term use as a sleeping pill.

Changes in lifestyle

It is often more effective to make structural changes in your lifestyle than to rely on medication. Think of a fixed sleep rhythm, avoiding stimulating substances before going to sleep, and creating a restful place to sleep. Sometimes meditation can also help to calm the mind and promote sleep.

It can be tempting to reach for sleeping pills as a quick solution, but it is important to tackle the underlying causes of sleep problems and to aim for a more lasting solution. Our sleep is a delicate balance that needs care and attention.

In practice

In practice people often do resort to a sleeping pill. The Dutch guideline on sleep problems for family doctors is restrained here: only for short-term sleeplessness with a clear cause and a lot of distress, and then once and briefly a short-acting medicine. The guideline does not recommend promethazine, quetiapine or antidepressants as sleeping pills.

If you do end up in a situation of longer use: some people then alternate between the different classes of medicines. This advice is not in the Dutch guideline. Always try to build in longer periods without use. Make sure you never end up in a situation where you can no longer do without a sleeping pill.

Prof. dr. Jim van Os, Chair Division Neuroscience, Utrecht University Medical Centre. Jim works at the interface of ‘hard’ brain science, health services research, art and subjective experiences of people with ‘lived experience’ in mental healthcare. 

Jim has been appearing on the Thomson-Reuter Web of Science list of ‘most influential scientific minds of our time’ since 2014. In 2014 he published his book ‘Beyond DSM-5‘, and in 2016 the book ‘Good Mental Health Care’. In 2026 he published 'Wat psychisch lijden is'.

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