Sleep Science
Sleep is not a single state you fall into and climb out of. It is four distinct conditions the brain cycles through, and the order they arrive in explains almost everything about how a night feels.
Sleep Science
It sits above the optic chiasm, it contains about 20,000 neurons, it keeps near-24-hour time in a dish with no external input, and the genes that run it won a Nobel Prize.
Nightmares & Disorders
Chronic nightmare disorder affects several per cent of adults, wrecks sleep, and is rarely asked about. The best-supported treatment takes about four sessions and involves changing the story while awake.
Sleep Science
A substantial part of your preferred sleep timing is genetic and cannot be trained away. The rest is light exposure, which can — and the difference matters for anyone fighting their alarm clock.
Sleep Science
Cognitive behavioural therapy for insomnia outperforms sedatives in the medium and long term, and its most effective component is the one that sounds like the worst possible advice.
Nightmares & Disorders
The airway collapses, oxygen falls, the brain briefly wakes to reopen it, and the whole sequence repeats until morning. The sleeper usually remembers none of it and wonders why they are so tired.
Sleep Science
The recommendation is a population range, not a personal prescription. Individual requirement varies substantially, a rare genetic variant permits four hours without penalty, and both ends of the curve carry risk.
Nightmares & Disorders
The mechanism is simple and well understood. The experience is one of the most frightening things a healthy person can undergo, and it has generated remarkably consistent folklore across the world.
Nightmares & Disorders
Parts of the brain wake up and others stay asleep. The result is a person who can walk, cook, drive and hold a conversation while being, in every meaningful sense, unconscious.
Sleep Science
A drainage network described only in 2012 appears to run far more actively during sleep than wakefulness. It is one of the most exciting findings in the field and one of the most over-claimed.
Sleep Science
Caffeine does not supply energy. It blocks the signal that tells you how tired you are, and the debt it conceals is still accruing underneath.
Nightmares & Disorders
It affects perhaps one in twenty adults, it is frequently dismissed as a habit, it has a well-established link to iron in the brain, and the standard treatment can make it dramatically worse over time.
Nightmares & Disorders
It is caused by the loss of about 20,000 neurons that produce a single neurotransmitter, it is probably autoimmune, and its most distinctive symptom is routinely mistaken for something psychiatric.
Sleep Science
The idea was tested seriously in the 1950s, discredited, revived by commercial products, and then partially rehabilitated by findings that are real, narrow, and much less useful than the advertising.
Sleep Science
Around one in five workers in industrialised economies works outside standard hours. Full circadian adaptation is rare, and the reason is that everyone goes home to daylight on their days off.
Sleep Science
A twenty-minute nap and a ninety-minute nap are different interventions with different mechanisms. Getting the length wrong is what produces the grogginess that makes people conclude naps do not suit them.
Nightmares & Disorders
A loud crash with no external source as you fall asleep. A violent whole-body twitch that jolts you awake. Both are common, both are benign, and both frighten people who have never heard of them.
Sleep Science
Light does suppress melatonin and shift the body clock. Whether your phone at bedtime does enough of it to matter is a more interesting question than the blue-light-filter industry suggests.
Nightmares & Disorders
Ordinary distressing memories lose their charge over successive nights. In post-traumatic stress disorder they do not, and the failure appears to happen during REM sleep itself.
Sleep Science
Volunteers deliberately exposed to a cold virus are several times more likely to become infected if they have been sleeping badly. The mechanism runs through cytokines, T-cells and antibody response.
Dream Research
Sleep architecture is measurably different in several psychiatric conditions, and so is dream content. In depression the REM changes are so consistent they were once proposed as a diagnostic marker.
Nightmares & Disorders
Twenty-odd sensors, a night in an unfamiliar bed, and a technician watching. Home testing has replaced it for many cases — but not for the ones where it matters most.
Nightmares & Disorders
Somniloquy is harmless and reveals nothing. Bruxism can destroy your teeth and is frequently a sign of something else. The two get grouped together and should not be.
Sleep Science
Core body temperature has to fall for sleep to begin, and the mechanism runs through the hands and feet. Which is why warm socks and a cool room are not contradictory advice.
Sleep Science
Newborns spend half their sleep in REM. By eighty, slow-wave sleep has largely disappeared and the clock has moved forward by hours. Almost none of this is optional.
Nightmares & Disorders
The single most useful thing to establish is what time it happened, because that distinguishes two entirely different phenomena requiring opposite responses.
Sleep Science
Sleep-maintenance insomnia has a different differential from difficulty falling asleep. Cortisol, alcohol, apnoea, the bladder and the body clock are all more likely explanations than anxiety alone.
Sleep Science
The metaphor of a debt implies a ledger that can be cleared. Recovery sleep is real, it is prioritised in a specific order, and some of the deficit does not appear to come back.
Sleep Science
Restrict sleep for two nights and appetite hormones shift measurably, food choices change, and reward responses to high-calorie food increase. The effect is real and smaller than the headlines.
Dream Research
After seventy years of laboratory research the confident claims are fewer than the popular literature suggests. Here is what has actually held up, and what has not.
