Understanding Sleep and Insomnia
A plain-language explainer on how sleep works, what insomnia is, why it takes hold, and how the harder we try to sleep the more it can elude us.
Written by Tarun Vermani, Trainee Clinical Psychologist Last reviewed
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Understanding Sleep and Insomnia
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How sleep works
Two things drive your sleep. The first is sleep pressure: the longer you are awake, the more your need for sleep builds up, a bit like growing hungrier the longer you go without food. The second is your body clock, an internal timer that decides when you feel sleepy and when you feel alert across the day and night. Together they decide when sleep comes. One important point: you cannot force yourself to sleep. You can only set up the right conditions and allow it to happen.
What insomnia is
Insomnia means having trouble falling asleep, staying asleep, or getting good-quality sleep, even when you have enough time and opportunity to rest. It usually comes with daytime effects too, such as feeling tired, low, irritable, or unable to concentrate. Insomnia is very common, and most people go through a patch of it at some point. The good news is that it responds well to treatment, and you do not have to simply put up with it.
Why it takes hold
It helps to think of three kinds of factor, sometimes called the three Ps. Predisposing factors are traits that make some people more prone to sleep problems, such as being a light sleeper or a natural worrier. A precipitating factor is the stress or life event that first triggers the poor sleep, like a bereavement, illness, or busy period. Perpetuating factors are the habits we pick up to cope, such as spending longer in bed, trying hard to sleep, or worrying about it. These coping habits are what turn a short bad patch into long-term insomnia.
The insomnia cycle
Once insomnia takes hold, a cycle often forms. A poor night leaves you tired and worried about sleep. So you try harder, go to bed earlier to catch up, and watch the clock. But spending more time in bed awake gradually weakens the link your brain makes between bed and sleep, so bed starts to feel like a place of frustration rather than rest. That leads to more poor nights, more worry, and more effort. The harder you try, the more sleep slips away.
What helps
The recommended first-line treatment for long-term insomnia is a form of CBT called CBT for insomnia, or CBT-I. It works by changing the habits that keep insomnia going. This includes stimulus control, which rebuilds the link between bed and sleep; matching your time in bed more closely to the sleep you are actually getting, so your sleep becomes deeper and more solid; building a wind-down routine; and, importantly, easing off the effort to sleep, since trying hard is part of the problem. These changes are made gradually, usually with a therapist.
Habits that can keep insomnia going
Many habits we pick up to cope with poor sleep quietly keep it going. Tick any that you recognise in yourself. Spotting them is the first step to changing them.
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When to use ‘Understanding Sleep and Insomnia’
‘Understanding Sleep and Insomnia’ is an interactive cognitive behavioural therapy (CBT) worksheet, most often used in CBT for insomnia and sleep problems.
It is designed to be used within therapy rather than as a standalone self-help tool: a therapist introduces it, works through it collaboratively, and helps make sense of what it surfaces. You can preview the full worksheet above, then assign it digitally for clients to complete between sessions on any device — or download it as a print-ready PDF.
How it works
Most people work through it in around 8 minutes. It moves through six short steps:
- How sleep works — Two things drive your sleep. The first is sleep pressure: the longer you are awake, the more your need for sleep builds up, a bit like…
- What insomnia is — Insomnia means having trouble falling asleep, staying asleep, or getting good-quality sleep, even when you have enough time and opportunity…
- Why it takes hold — It helps to think of three kinds of factor, sometimes called the three Ps. Predisposing factors are traits that make some people more prone…
- The insomnia cycle — Once insomnia takes hold, a cycle often forms. A poor night leaves you tired and worried about sleep. So you try harder, go to bed earlier…
- What helps — The recommended first-line treatment for long-term insomnia is a form of CBT called CBT for insomnia, or CBT-I. It works by changing the…
- Habits that can keep insomnia going — Many habits we pick up to cope with poor sleep quietly keep it going. Tick any that you recognise in yourself. Spotting them is the first…
Completed on the Formulate platform, your client's answers are saved automatically and shared straight back to you, so you can review them before the next session rather than waiting for a paper copy to come back.
The CBT approach behind it
In common with other CBT methods, ‘Understanding Sleep and Insomnia’ works by noticing the links between situations, thoughts, feelings, physical sensations and behaviour — and finding practical ways to change unhelpful patterns. The aim is not positive thinking but a clearer, shared understanding of what keeps a difficulty going — and practical, testable ways to change it.
Because it is a CBT tool it stays focused on the here-and-now links between thoughts, feelings, the body and behaviour, and it works best as one part of a wider course of therapy rather than as advice or a diagnosis.
Evidence & sources
This worksheet is grounded in established cognitive behavioural therapy theory and practice. Key sources include:
- Borbély, A.A. (1982). A two process model of sleep regulation. Human Neurobiology, 1(3), 195-204.
- Spielman, A.J., Caruso, L.S., & Glovinsky, P.B. (1987). A behavioral perspective on insomnia treatment. Psychiatric Clinics of North America, 10(4), 541-553. doi:10.1016/S0193-953X(18)30532-X
- Morin, C.M. (2004). Cognitive-behavioral approaches to the treatment of insomnia. Journal of Clinical Psychiatry, 65(Suppl 16), 33-40.
For use alongside professional support
Formulate provides educational CBT resources for use with a qualified therapist. They are not a substitute for professional assessment, diagnosis, or crisis care.
If you need urgent help now:
- Emergency services: 999 — if you or someone else is in immediate danger
- Samaritans: 116 123 — free, day or night, 365 days a year
- SANEline: 0800 689 5555 — 4:30pm–10:30pm, every day
More Insomnia / Sleep worksheets
View all Insomnia / Sleep worksheets →Insomnia / Sleep
Insomnia Formulation (Spielman 3P Model)
A formulation based on Spielman's 3P model — mapping predisposing, precipitating, and perpetuating factors that maintain insomnia.
Insomnia / Sleep
Sleep Diary
The standard CBT-I sleep diary — record bed times, sleep times, wake times, and daytime functioning to track patterns and calculate sleep efficiency.
Insomnia / Sleep
Sleep Efficiency Tracker
Calculate and track sleep efficiency (time asleep ÷ time in bed × 100) — the key metric for CBT-I sleep restriction therapy.
Insomnia / Sleep
Sleep Window Prescription & Tracking
Set and track your prescribed sleep window as part of sleep restriction therapy — with weekly adjustments based on sleep efficiency.
Insomnia / Sleep
Stimulus Control Plan
The core stimulus control rules for CBT-I — rebuilding the association between bed and sleep.
Insomnia / Sleep
Sleep Hygiene Assessment
Assess current sleep hygiene practices and identify areas for improvement.
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