Factsheet: Sleep

This factsheet is available in a downloadable PDF here. 

Table of Contents

How Long does Insomnia Last?
How Much Sleep should You Get?
Symptoms of Insomnia
Causes of Insomnia


Sleep is a state of consciousness, which gives your body time to rest. While you are asleep, your body goes through different sleep stages in a cycle that lasts approximately 90 minutes, and may go through five of these cycles in a night. The sleep stages are:

  • Drowsiness
  • Light sleep
  • Deep sleep
  • Dreaming – also known as rapid eye movement (REM) sleep


Insomnia is difficulty getting to sleep or staying asleep for long enough to feel refreshed the next morning. This happens despite having enough opportunity to sleep.

The most common problem in young people with insomnia is difficulty falling asleep (sleep-onset insomnia). An insomniac may also experience:

  • Waking in the night (most common in older people)
  • Not feeling refreshed after sleep and not being able to function normally during the day, feeling irritable and tired and finding it difficult to concentrate
  • Waking when you have been disturbed from sleep by pain or noise
  • Waking early in the morning (the least common type of sleep disturbance)

Nearly everyone has problems sleeping at some point in their life and it is thought that a third of people in the UK have bouts of insomnia. Insomnia appears to be more common in women and more likely to occur with age.

There are a number of possible causes for insomnia, such as anxiety, a disrupted sleeping environment, or an underlying physical condition or mental health problem.

How Long does Insomnia Last?

Insomnia can last for days, months or even years. It can be split into:

  • Short-term insomnia, which lasts for one to four weeks
  • Long-term (or persistent) insomnia, which lasts for four weeks or longer

How Much Sleep Should You Get?

Every individual is different, so it is hard to define what normal sleep is for you. Factors influencing the amount of sleep you need include your age, lifestyle, diet and environment. For example, newborn babies can sleep for 16 hours a day, while school-age children need an average of 10 hours sleep.

Most healthy adults sleep for an average of seven to nine hours a night. As you get older, it is normal to need less sleep. Most people over 70 need less than six hours sleep a night, and they tend to be light sleepers.

Symptoms of Insomnia

Depending on the type of sleeping problem you have, symptoms of insomnia can include:

  • Lying awake for a long time at night before getting to sleep
  • Waking up several times in the middle of the night
  • Waking up early in the morning (and not being able to get back to sleep)
  • Feeling tired and not refreshed by sleep
  • Not being able to function properly during the day and having difficulty concentrating
  • Being irritable

Causes of Insomnia

There are many possible causes of insomnia, outlined below.

Stressful Event

For some people, their insomnia starts in response to a stressful event and continues even when the stress has been resolved. This is because they have learnt to associate the sleeping environment with a state of being alert.

Causes of stress can be:

  • Situational – for example, worrying about work, money or health
  • Environmental, such as noise
  • Death or illness of a loved one


Psychiatric Problem

Underlying mental health problems can affect your sleeping patterns, including:

  • Mood disorders, such as depression or bipolar disorder
  • Anxiety disorders, such as generalised anxiety, panic disorder or post-traumatic stress disorder
  • Psychotic disorders, such as schizophrenia

Physical Condition

Insomnia can be caused by an underlying physical condition, including:

  • Heart disease, such as angina or heart failure
  • Respiratory disease, such as chronic obstructive pulmonary disease or asthma
  • Neurological disease, such as Alzheimer’s or Parkinson’s disease
  • Hormone problems, such as an over-active thyroid
  • Joint or muscle problems, such as fibromylagia or arthritis
  • Gastrointestinal disease, such as gastro-oesophageal reflux disease or irritable bowel syndrome
  • Problems with the genital or urinary organs, such as incontinence or an enlarged prostate
  • Sleep disorders, such as restless legs syndrome, narcolepsy or sleep apnoea
  • Chronic (long-term) pain

Drug and Substance Misuse

This includes the misuse of:

  • Alcohol
  • Recreational drugs
  • Caffeine
  • Nicotine


Some prescribed or over-the-counter medicines can cause insomnia, including:

  • Antidepressants
  • Epilepsy medicine
  • Medication for high blood pressure, such as beta-blockers
  • Hormone treatment
  • Non-steroidal anti-inflammatory drugs (NSAIDs)
  • Stimulant drugs, such as methylphenidate to treat ADHD or modafinil to treat narcolepsy
  • Some medicines for asthma, such as salbutamol, salmeterol and theophylline

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