Notes

This book gives general information. It isn't medical advice, and it's no substitute for a doctor who knows your situation. NHS guidance is quoted as I found it in September 2026 and applies to England.

I've kept sources out of the chapters where I could so they read easily. Here they are by chapter, with the limits I'm aware of. Unless I say otherwise, I read the published summary of each paper and not the full text. I checked each paper for a retraction or correction notice in September 2026 and found none. Where a chapter isn't listed, it rests on my own reasoning. That includes chapters 1, 5, 6 and 16, and the method in chapters 12 to 14. The people, sums of money and times in the examples are invented for illustration.

Before you start. When to see a GP about sleep is from the NHS page "Insomnia". The symptoms of sleep apnoea are from the NHS page "Sleep apnoea". Waking very early as a symptom of depression is from the NHS page "Symptoms: depression in adults". Urgent help routes are from the NHS page "Where to get urgent help for mental health".

Chapter 2. Harvey, "A cognitive model of insomnia", Behaviour Research and Therapy 40, 2002, pages 869 to 893. It's a theoretical paper about people with insomnia. The list of five attractions is mine.

Chapter 3. Wehr, "In short photoperiods, human sleep is biphasic", Journal of Sleep Research 1, 1992, pages 103 to 107. The summary doesn't give the number of volunteers or the length of the experiment. Ekirch, "Sleep we have lost: pre-industrial slumber in the British Isles", American Historical Review 106, 2001, beginning on page 343. I haven't read the article, and my description of his sources and of what people did in the interval is from general accounts of his work. The dispute is set out in Ekirch, "Reflections on 'Have we lost sleep?'", Medical History 68, 2024, pages 254 to 262, which replies to an article by Niall Boyce in the same journal in 2023. I read the summary of the reply only. That sleep runs in cycles with brief awakenings, and that night waking increases with age, are standard statements in sleep science which I haven't sourced. That quiet rest has some value is my opinion.

Chapter 4. Boivin, Czeisler, Dijk, Duffy, Folkard, Minors, Totterdell and Waterhouse, "Complex interaction of the sleep-wake cycle and circadian phase modulates mood in healthy subjects", Archives of General Psychiatry 54, 1997, pages 145 to 152. There were 24 volunteers, 16 men and 8 women. The study also found that the effect of time awake on mood depended on the body clock phase. Tubbs, Fernandez, Grandner, Perlis and Klerman, "The mind after midnight: nocturnal wakefulness, behavioral dysregulation, and psychopathology", Frontiers in Network Physiology 1, 2022, article 830338. I read the full text. The timing of the trough in positive mood, the night-time peak in negative mood and the account of impaired executive function are the review's summaries of other studies, which I haven't read individually. The authors present their overall account as a hypothesis. The comparison with a colleague planning after a long day and several drinks is mine, and it's loose.

Chapter 7. Harvey 2002 as above.

Chapter 8. The research on thought suppression began with Wegner, Schneider, Carter and White, "Paradoxical effects of thought suppression", Journal of Personality and Social Psychology 53, 1987, pages 5 to 13. Later work has found the effect to be smaller and less consistent than first reported. Harvey and Payne, "The management of unwanted pre-sleep thoughts in insomnia: distraction with imagery versus general distraction", Behaviour Research and Therapy 40, 2002, pages 267 to 277. There were 41 participants, studied on one night. The researchers had predicted that the general distraction group would do worse than the group with no instruction, and that prediction wasn't supported. Espie, Broomfield, MacMahon, Macphee and Taylor, "The attention-intention-effort pathway in the development of psychophysiologic insomnia: a theoretical review", Sleep Medicine Reviews 10, 2006, pages 215 to 245. The NHS advice is from the Every Mind Matters page "How to fall asleep faster and sleep better".

Chapter 9. Tang, Schmidt and Harvey, "Sleeping with the enemy: clock monitoring in the maintenance of insomnia", Journal of Behavior Therapy and Experimental Psychiatry 38, 2007, pages 40 to 55. I couldn't obtain the paper or a summary, and the chapter says so. The advice to keep clocks out of view is from the NHS page named above. That people overestimate how badly a poor night will affect the next day is part of Harvey's 2002 model. That light at night signals daytime to the body is general knowledge, and the NHS insomnia page advises against using devices right before bed for that reason.

Chapter 10. Palmer, Bower, Cho, Clementi, Lau, Oosterhoff and Alfano, "Sleep loss and emotion: a systematic review and meta-analysis of over 50 years of experimental research", Psychological Bulletin 150, 2024, pages 440 to 463. The studies involved experimentally restricted or disrupted sleep, which isn't quite the same as a bad night at home. Conditioned arousal is named in Espie and colleagues, above. The five or six hours a week is arithmetic on invented figures.

Chapter 11. Carney and Waters, "Effects of a structured problem-solving procedure on pre-sleep cognitive arousal in college students with insomnia", Behavioral Sleep Medicine 4, 2006, pages 13 to 28. There were 33 participants. The outcome was self-reported mental arousal in bed, not measured sleep. Scullin, Krueger, Ballard, Pruett and Bliwise, "The effects of bedtime writing on difficulty falling asleep: a polysomnographic study comparing to-do lists and completed activity lists", Journal of Experimental Psychology: General 147, 2018, pages 139 to 146. The research on unfulfilled goals is Masicampo and Baumeister, "Consider it done! Plan making can eliminate the cognitive effects of unfulfilled goals", Journal of Personality and Social Psychology 101, 2011, pages 667 to 683. The NHS suggestion is from the Every Mind Matters page named above. The idea that the night shift is a displaced daily review is my interpretation.

Chapter 12. The handover is adapted from the constructive worry procedure of Carney and Waters. My version hasn't been tested. Scullin's participants wrote at bedtime. I suggest early evening, following Carney and Waters.

Chapter 13. Getting up after around twenty minutes and returning when sleepy is from the NHS Every Mind Matters page. It's a standard part of insomnia treatment, usually called stimulus control. The labelling, the single answer and the pad are mine.

Chapter 14. Gollwitzer and Sheeran, "Implementation intentions and goal achievement: a meta-analysis of effects and processes", Advances in Experimental Social Psychology 38, 2006, pages 69 to 119. The rule and its parts haven't been tested together, and what I say to expect is my expectation and not a finding.

Chapter 15. Trauer, Qian, Doyle, Rajaratnam and Cunnington, "Cognitive behavioral therapy for chronic insomnia: a systematic review and meta-analysis", Annals of Internal Medicine 163, 2015, pages 191 to 204. The trials excluded people whose insomnia came with other medical or psychiatric conditions. Ebrahim, Shapiro, Williams and Fenwick, "Alcohol and sleep I: effects on normal sleep", Alcoholism: Clinical and Experimental Research 37, 2013, pages 539 to 549. The NHS statements on treatment, sleeping pills, alcohol and caffeine are from its "Insomnia" page. Night sweats are listed on the NHS page "Symptoms of menopause and perimenopause". Self-referral is from the NHS page "NHS talking therapies for anxiety and depression". The paragraph on dark thoughts at night draws on Tubbs and colleagues, above.