Glossary
Jargon-free, mostly – and explained where it isn’t
A lot of the language around sleep and neurodivergence gets thrown around without much explanation. Here’s what the terms used across this site actually mean, in plain language. If you land on a single page from a search and hit a term you don’t recognise, this is the page to jump to.
ADHD
a difference in the way the brain manages attention, energy and impulse. You’re born with it, and it runs in families. It’s common – around one in twenty people – and doesn’t look the same in everyone; the quieter, racing-mind version is just as real as the restless, fidgety one.
Actigraphy
a way of measuring sleep and activity using a small wrist-worn sensor, similar to a fitness tracker, often used in sleep research instead of relying on someone’s memory of their night.
Alexithymia
difficulty identifying and naming your own emotions. It can happen with or without being neurodivergent, and it often overlaps with interoception difficulties.
AuDHD
the combined experience of being Autistic and having ADHD. Not simply “a bit of both” – living with both often means holding two sets of needs that pull in different directions at once.
Autistic / autism
a difference in the way the brain takes in the world: sensory information, social signals, patterns. Something you’re born with, not something caused by upbringing or environment. We use identity-first language (“Autistic person”) because that’s what most of the Autistic community prefers.
Camouflaging / masking
consciously or unconsciously hiding or suppressing traits (stimming, natural expression, tone of voice) to appear less visibly Autistic or ADHD. Takes real effort and has a measurable cost, including for sleep. (See Masking and rest)
CBT-I (cognitive behavioural therapy for insomnia)
A structured approach to long-term insomnia, and the recommended first step for it in the UK. It works on the habits, timings and worries that keep insomnia going, and often needs adapting for neurodivergent people.
Chronic insomnia
Trouble getting to sleep, staying asleep or waking too early, on at least three nights a week for three months or more, that affects how you get on during the day.
Chronotype
your natural leaning towards earlier or later sleep, largely set by biology rather than habit. Ranges from “morning types” (larks) to “evening types” (night owls), with most people somewhere in between.
Circadian rhythm / body clock
the roughly 24-hour internal cycle that governs when you feel alert or sleepy, among other things. Reset daily, mostly by light.
Deep pressure stimulation
firm, even pressure across the body, the mechanism behind weighted blankets. Thought to help calm an overactive nervous system; the evidence is stronger for anxiety than for sleep itself. (See the blog post on weighted blankets)
Delayed sleep phase
the clinical name for a body clock set hours later than the world runs on. Common in ADHD; not the same as insomnia, since sleep isn’t broken, just later than expected.
Hypnagogic imagery
Vivid, dream-like pictures or sounds as you drift off. Common, and usually a sign of the brain moving between waking and sleep.
Melatonin
A hormone your body makes in the evening as light fades. It tells your body that night has arrived, and works as a timing signal rather than a sleeping pill. In the UK, melatonin you take is a prescription-only medicine. Products sold online are often poorly controlled: one study found their melatonin content ranged from 83% below to 478% above the label, and another found 22 of 25 gummy products were inaccurately labelled. Talk to your GP before taking it.
Developmental coordination disorder (DCD) / dyspraxia
a difference affecting movement and coordination. Can make finding a comfortable, still position for sleep harder.
Ehlers-Danlos syndrome (EDS)
a group of inherited conditions affecting connective tissue, often causing joint hypermobility, pain, and other symptoms that can make comfortable sleep positions hard to find or hold. (The most common type, hypermobile EDS, doesn’t yet have a single identified genetic cause – diagnosis is based on symptoms and examination, not a genetic test.)
Ferritin
the protein that stores iron in your body. A ferritin blood test (done through your GP) is how low iron is diagnosed, which matters because low iron is linked to restless legs syndrome.
Hypnic jerk
A sudden twitch or jolt as you fall asleep, sometimes with a feeling of falling. Very common, and more likely when you’re stressed, short of sleep or have had caffeine late in the day.
Insomnia
trouble falling or staying asleep, night after night, even with the time and opportunity for it.
Interoception
the sense that picks up signals from inside your body: hunger, tiredness, pain, a racing heart. Works differently for a lot of neurodivergent people – signals can arrive late, muted, or overwhelming.
ME/CFS (myalgic encephalomyelitis / chronic fatigue syndrome)
a long-term condition causing persistent, often severe fatigue that doesn’t improve with rest, along with other symptoms. Sleep in ME/CFS frequently doesn’t feel restorative even after a full night.
Melatonin
the hormone your body releases in the evening to signal that it’s night. With ADHD, this release often happens later than expected.
Neurodivergent / neurodiversity
neurodiversity is the idea that there’s natural variation in how brains and nervous systems work. “Neurodivergent” describes someone whose brain works in a way that diverges from what’s considered ty
OCD (obsessive-compulsive disorder)
a condition involving intrusive thoughts and compulsions. If this is what’s keeping you awake, it needs its own specialist support rather than general sleep advice.
Perimenopause
the years before periods stop, when hormone levels fluctuate and fall. Can start in the late thirties or forties and often disrupts sleep well before other symptoms appear.
POTS (postural orthostatic tachycardia syndrome)
a condition affecting the autonomic nervous system, causing a rapid heart rate and other symptoms on standing. Can make it hard for the body to settle at night.
Restless legs syndrome (RLS)
an uncomfortable urge to move the legs, usually worse in the evening, that can make it hard to fall asleep. Linked to low iron and more common in ADHD and autism.
Revenge bedtime procrastination
staying up late to reclaim a sense of free time after a day with none, even though it costs you sleep. Very common in ADHD.
Second wind
a burst of alertness that can appear if you stay awake past your natural sleep window. Not a sign you don’t need sleep – another window usually comes round as your body clock carries on.
Sleep apnoea
breathing that repeatedly stops and starts during sleep, often with loud snoring or gasping. Needs medical assessment, and can sometimes be mistaken for ADHD.
Sleep pressure
your body’s building need for sleep, which increases the longer you’re awake and resets once you sleep.
Sleep-state misperception
the gap between how much you actually slept and how much it felt like you were awake. Very common in light or broken sleep.
Sleep window
the point where sleepiness and your body clock line up, making it easier to fall asleep. Miss it and you may get a “second wind” before the next one comes round.
Social jetlag
The gap between your sleep timing on work days and free days. Sleeping in at weekends pays back some lost sleep but shifts your body clock later, which is why Sunday night is often the hardest.
Time blindness
Difficulty sensing how much time has passed, common in ADHD. The five-minute break that turns into 45 minutes.
Revenge bedtime procrastination
Staying up late, though tired, to claim back time that feels like yours. It often follows a stressful or overscheduled day.
Sleep inertia
The heavy, foggy feeling after waking, before your brain fully comes online. It can last longer when you wake during your body’s night, which often happens with a late body clock.
Sleep paralysis
A brief spell of being unable to move as you fall asleep or wake up, sometimes with vivid imagery. Frightening, but usually harmless. See your GP if it happens often, is very distressing or comes with a lot of daytime sleepiness.
Sleep restriction
Part of CBT-I. Time in bed is temporarily limited to roughly the time you’re actually asleep, so that sleep pressure builds and sleep becomes more settled, then widened as sleep improves. It isn’t safe for everyone and is best done with support.
Worry time
A set 15–20 minutes early in the evening, away from bed, for writing down or saying out loud everything on your mind. It gives the thoughts somewhere to go, so they’re less likely to arrive at bedtime.