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    Sleep, without the myths

    How much sleep do you really need? Does melatonin work, and why can't you buy it in a UK chemist? This independent guide reads the trials, grades the evidence behind every claim and explains what actually helps you sleep, from caffeine cut-offs to the therapy the NHS recommends for insomnia.

    See which sleep aids workHow much sleep you need
    A bright moon over a dark mountain lake, its light making a long silver path across the water
    Moonlight over a lake. Photo: Olivier Miche, CC0
    7–9h
    a night is what most adults need, according to the NHS
    90min
    or so is the length of each sleep cycle, four to six a night
    4×
    more colds in people who slept under six hours, in a virus-exposure trial
    1 in 3
    UK adults report insomnia symptoms; CBT is the first treatment NICE advises

    What good sleep does for you

    Each claimed benefit, graded by the quality of the studies behind it. Most of the evidence links short sleep with worse health; trials show some of it is cause and effect, but not all.

    1. Memory, attention and learning

      Many controlled lab trials show that cutting sleep impairs attention, reaction time and learning, and that sleep after learning helps memories stick.

      Strong

    2. Mood and mental health

      Insomnia roughly doubles the later risk of depression, and a trial of 3,755 students found treating insomnia also eased paranoia, low mood and anxiety.

      Moderate

    3. Immune system and infections

      People who slept under 6 hours were about four times as likely to catch a cold after being given the virus, and short sleep weakened responses to vaccines.

      Moderate

    4. Weight and appetite

      Lab trials show short sleep raises hunger hormones and makes people eat about 385 more calories a day. Long-term weight effects come from observational studies.

      Moderate

    5. Heart and blood pressure

      Studies of nearly half a million people link short sleep with more heart disease and stroke. Lab trials show sleep loss raises stress hormones and the nerve activity that drives blood pressure.

      Moderate

    6. Type 2 diabetes

      Short and broken sleep predicted type 2 diabetes in studies of over 100,000 people, and restricting sleep worsens blood sugar control in lab trials.

      Moderate

    7. Dementia

      Short sleep in mid-life was linked with more dementia 25 years later in one large British study. Cause and effect are unclear.

      Weak

    • No good evidence
    • Weak evidence
    • Moderate evidence
    • Strong evidence

    Read why sleep matters

    One night, in one chart

    You don't sleep in one block. You pass through light, deep and dreaming sleep four to six times a night, with most deep sleep early on and longer dreams towards morning. What each stage does.

    REM sleep30%
    Vivid dreams. The brain is busy but most muscles are switched off.
    Light sleep (N1)3%
    The doze between waking and sleep. A few minutes at a time.
    Light sleep (N2)48%
    About half the night. Heart rate and temperature drop.
    Deep sleep (N3)20%
    Slow brain waves. Hardest to wake from; most of it comes early.
    An illustrative night for a healthy adult, based on the average proportions in sleep-lab studies. Real nights vary, and deep sleep shrinks with age.

    Sleep aids, graded

    Most pills and remedies sold for sleep have little good evidence behind them, and the ones that work best are prescription only for a reason. The most effective treatment for long-term insomnia isn't a pill at all: it's a short course of CBT, which the NHS now offers as an app.

    Compare every sleep aid
    1. CBT for insomnia (not a pill, for comparison)Strong
    2. Prescription sleeping pillsStrong
    3. MelatoninModerate
    4. MagnesiumWeak
    5. ValerianWeak
    6. ChamomileWeak
    7. LavenderWeak
    8. Weighted blanketsWeak
    9. Nytol and other antihistaminesWeak

    How much sleep, at every age

    Babies need twice as much as adults, teenagers need more than their parents, and older people need about the same as other adults even though they tend to sleep less deeply. The full guide.

    1. School age6–13 years
    2. Teenagers14–17 years
    3. Young adults18–25 years
    4. Adults26–64 years
    5. Older adults65 and over
    Solid bars: hours recommended in 24 hours, including naps for children. Pale band: may suit some people. From the US National Sleep Foundation's expert panel; the NHS gives 7 to 9 hours for adults.

    Start here

    Five guides, in the order most people need them: how sleep works, why it matters, how to sleep better, which aids help and what to do about sleep problems.

    1. Long-exposure star trails curving over a lake and a rocky, wooded shore, with the first light of dawn on the horizon
      How sleep worksWhat happens while you sleep, the two systems that decide when you feel sleepy, and how much sleep children and adults need.
    2. A woman lying back on blue pillows with her eyes closed and a relaxed smile
      Why sleep mattersWhat good sleep does for your heart, weight, immune system, memory, mood and blood sugar, with each claim graded by the strength of the evidence.
    3. A calm, uncluttered bedroom with white bedding, a wooden headboard and soft daylight through a tall window
      How to sleep betterWhich everyday changes really improve sleep, from a fixed wake time and morning light to caffeine, alcohol, screens, exercise, bedroom heat and naps.
    4. A steaming cup of tea on a tray in bed, beside an open book and a small posy of flowers
      Sleep aids and supplementsMelatonin, magnesium, valerian, chamomile, lavender, Nytol, sleeping pills and weighted blankets, each graded on what trials show, with UK rules.
    5. A woman’s face in near darkness, eyes closed, lit by a faint glow
      Sleep problemsThe common sleep problems in the UK, how to tell them apart, which treatments work, and when poor sleep is a reason to see a GP.
    6. How we grade the evidenceEvery health claim on this site carries one of four grades. Here is what each one means and how we decide.

    Photographs from StockSnap (CC0): Olivier Miche, Yinan Chen, Bruce Mars, Burst, Carli Jean, Maxime Caron.

    Questions people ask

    Short answers, each linked to the guide that explains it in full.

    How many hours of sleep does an adult need?

    The NHS and the US National Sleep Foundation both say 7 to 9 hours a night for most adults, with 7 to 8 for people over 65. Some people do well on a little less or a little more. If you wake refreshed and stay alert during the day, you are probably getting enough.

    What are the benefits of getting enough sleep?

    The best-proven benefits are for the brain: better attention, reaction times, learning and memory. There is also good evidence that enough sleep helps keep appetite, blood sugar, blood pressure and mood in check and helps the immune system respond to infections and vaccines.

    What is the fastest way to fall asleep?

    There is no reliable trick. What helps most is going to bed only when sleepy, keeping the bedroom dark and cool, and not lying in bed awake for long: if you can't sleep after about 20 minutes, get up, do something calm in dim light and go back when sleepy. That is part of CBT for insomnia.

    What is the best sleep aid in the UK?

    For insomnia that has lasted months, the best-proven treatment is not a pill but CBT for insomnia, which NICE recommends first and the NHS offers as the Sleepio app in many areas. For a short bad patch, a pharmacist can advise on short-term options. No supplement has strong evidence behind it.

    How do I know if I have a sleep disorder?

    Signs worth taking seriously are trouble sleeping on most nights for three months or more, someone noticing you stop breathing or gasp in your sleep, falling asleep in the day without meaning to, or an urge to move your legs that keeps you awake. A GP can assess you and refer you to a sleep clinic if needed.