Why You Can’t Sleep: Evidence-Based Fixes

Last reviewed: September 2026. General information, not medical advice — see our Disclaimer.

Most sleep advice is a list of tips. Darken the room, avoid caffeine, put the phone down. All reasonable, and none of it helps much if the reason you are awake is not the one those tips address.

Sleeplessness has a handful of common causes, and they respond to different things. Working out which one you have is most of the work.

How much sleep is actually needed

The U.S. Centers for Disease Control and Prevention recommends that adults get 7 or more hours per night, with different ranges for children and teenagers. Their summary of recommended sleep duration by age is the reference point most other guidance is built on.

Two caveats worth holding. Individual need varies within a range, so someone functioning well on seven hours is not doing it wrong. And “hours in bed” is not the same as hours asleep — the gap between the two is precisely what makes insomnia exhausting.

The four common patterns

Pattern	What it looks like	Usually points to
Cannot fall asleep	Awake 30+ minutes at the start	Arousal, anxiety, or a body clock set later than your schedule
Cannot stay asleep	Waking at 3am, unable to return	Stress, alcohol, sleep apnoea, sometimes depression
Waking too early	Up at 4am, fully awake	Body clock shifted earlier, or low mood
Sleeping but unrefreshed	Full night, still exhausted	Fragmented sleep, often a breathing problem

That last row is the one most often misread as needing more sleep. If you consistently spend eight hours in bed and wake exhausted, the issue is more likely to be sleep quality than quantity, and that is a medical question rather than a habits question.

Cause one: your body clock is not aligned with your schedule

Your circadian rhythm is set largely by light. Bright light in the morning pulls the clock earlier; light in the evening pushes it later. Someone who gets no morning light and plenty of evening light will tend to drift later, and then struggle to sleep at a conventional hour.

What helps, specifically:

• Daylight within an hour of waking, outdoors, for 10 to 20 minutes. Outdoor light is dramatically brighter than indoor lighting even on an overcast day.
• A consistent wake time, including weekends. Wake time anchors the clock more reliably than bedtime does.
• Dimmer evenings. Reducing overall light for the last hour or two matters more than filtering the colour of a screen.

Shifting a body clock takes days, not one night. Expect a week before judging whether it is working.

Cause two: arousal — the racing mind

This is the pattern where you are tired, you get into bed, and your mind immediately becomes busy. The mechanism is that the bed has become associated with being awake and trying, which is itself activating.

The counterintuitive intervention is to spend less time in bed, not more:

• If you are awake for around 20 minutes, get up. Go to another room, keep the lights low, do something dull, return when sleepy. This breaks the association between the bed and lying there frustrated.
• Use the bed for sleep only. Not work, not scrolling, not worrying.
• Move the worrying earlier. Ten minutes with a notebook in the evening — concerns and the next action for each — gives the mind somewhere to have put them.

These are components of cognitive behavioural therapy for insomnia, which is the approach generally recommended as the first-line treatment for chronic insomnia. The National Heart, Lung, and Blood Institute describes insomnia and its treatment in its health topic on insomnia.

Cause three: substances doing something other than what you think

Caffeine

Caffeine has a long half-life, which means a meaningful amount is still circulating many hours after the last cup. An afternoon coffee can measurably affect sleep that night even in people who report no difficulty falling asleep — the effect shows up in sleep quality rather than in how quickly you drop off.

If you drink coffee and sleep badly, a two-week trial with nothing after midday is more informative than any amount of theorising.

Alcohol

Alcohol is a sedative, so it shortens the time to fall asleep. It then disrupts the second half of the night, which is why a drink before bed frequently produces a 3am waking. If your pattern is falling asleep easily and waking in the early hours, this is worth ruling out first.

Screens

The screen problem is less about blue light than about what the screen contains. A device is engaging, sometimes stressful, and easy to keep using. Removing the device from the bedroom addresses that more effectively than a colour filter.

Cause four: something medical

Some sleeplessness is not a habits problem, and continuing to optimise routines wastes time that should be spent getting assessed.

Worth talking to a doctor if:

• You snore heavily, gasp or stop breathing in your sleep, or wake unrefreshed despite adequate time in bed
• Difficulty sleeping has occurred at least three nights a week for three months or more
• You have unpleasant sensations in your legs at night that improve with movement
• Low mood, loss of interest, or persistent anxiety accompany the sleep problem
• Daytime sleepiness is affecting your driving or your work

Sleep and mental health interact in both directions: poor sleep worsens mood and anxiety, and both worsen sleep. The National Institute of Mental Health covers that relationship and when to seek help in its overview of caring for your mental health.

What to try first, in order

1. Fix the wake time. Same time daily for two weeks, regardless of how the night went.
2. Get morning light within an hour of waking.
3. Move caffeine to before midday for two weeks and observe.
4. Apply the 20-minute rule rather than lying awake.
5. Take the phone out of the bedroom.
6. If nothing has changed after a month, or if any of the medical flags apply, see a doctor rather than trying the next tip.

Stress and anxiety are among the most common drivers of the racing-mind pattern, and they are worth addressing directly rather than only through sleep. Our guide on telling anxiety and stress apart covers what helps each, and the warning signs of burnout covers the case where exhaustion is coming from work rather than from sleep.

Related guides

• Anxiety vs. stress — if the reason you are awake is a mind that will not stop.
• Burnout: the warning signs most people miss — when the exhaustion is not really about sleep.
• How to find a therapist — including how to find a practitioner who offers CBT for insomnia.

Frequently asked questions

How many hours of sleep do adults need?

The CDC recommends 7 or more hours per night for adults. Individual need varies within a range, and time in bed is not the same as time asleep.

Should I get out of bed if I cannot sleep?

Generally yes. Lying awake for long periods strengthens the association between the bed and being awake. Getting up after roughly 20 minutes and returning when sleepy is a standard component of CBT for insomnia.

Does blue light from screens cause insomnia?

The content and engagement matter more than the colour of the light for most people. Removing the device from the bedroom tends to help more than a filter.

When does sleeplessness count as insomnia?

Chronic insomnia is generally described as difficulty sleeping at least three nights a week for three months or longer. That threshold is a reason to see a doctor rather than to keep adjusting habits.

Does alcohol help you sleep?

It shortens the time to fall asleep and disrupts the later part of the night, which commonly produces early-hours waking. It is a frequent and easily tested cause.

Is it normal to wake during the night?

Brief awakenings are normal and most people do not remember them. The concern is being awake for extended periods, or waking unrefreshed despite enough time in bed.