Insomnia is trouble falling asleep, staying asleep or waking too early that happens although there is time and a suitable place to sleep, and that causes problems in the day such as tiredness, poor concentration or low mood. It counts as chronic insomnia disorder when it happens at least three nights a week for at least three months. Roughly one adult in three reports at least one insomnia symptom, but depending on the survey and the definition between about 4% and 23% meet criteria for the disorder.
What is insomnia? In medical terms it is persistent difficulty falling asleep, staying asleep or waking too early, despite enough time and a suitable place to sleep, together with problems in the day such as tiredness, poor concentration or low mood. A few bad nights do not make it a disorder: chronic insomnia is diagnosed when the trouble occurs at least three nights a week for at least three months.
This is the definition page. It covers the wording of the criteria, the types of insomnia, how common each version is in surveys and where insomnia ends and plain lack of sleep begins. Why insomnia starts and keeps going is in What causes insomnia?, and a way to check your own nights against the criteria is in the insomnia test.
What is insomnia? The definition clinicians use
Two manuals set the definition. The International Classification of Sleep Disorders, third edition (ICSD-3) of the American Academy of Sleep Medicine is described as the key reference for diagnosing sleep disorders, and it lists insomnia disorders as one of seven major categories. The DSM-5, the psychiatric manual, uses a very similar set of requirements. Both describe the same five-part picture.
Sateia MJ. International classification of sleep disorders-third edition: highlights and modifications. Chest 2014. PMID 25367475
| Part | In plain words | Reading note |
|---|---|---|
| Sleep complaint | Trouble falling asleep, trouble staying asleep, or waking earlier than wanted and not getting back to sleep | Based on your report. The manuals say 'difficulty', not a number of minutes. |
| Opportunity | The trouble occurs although there is enough time in bed and a suitable setting | This is what separates insomnia from being short of sleep. |
| Daytime effect | Fatigue, trouble concentrating, mood changes or distress about sleep | Without a daytime effect, the diagnosis is not made. |
| Frequency and duration | At least three times a week; at least three months for the chronic form | Shorter spells are classed as short-term insomnia. |
| Not better explained | Another sleep disorder, medical condition, medicine or substance does not account for it | This is why a clinician looks for sleep apnea or limb movements first. |
The thresholds in the table are the ones researchers use when they want a precise count. In a national online survey of 2,044 Australian adults, chronic insomnia was defined as sleep symptoms and daytime impairment at least three times a week, present for at least three months, with adequate sleep opportunity (at least 7.5 hours in bed).
Appleton SL, Reynolds AC, Gill TK, et al. Insomnia Prevalence Varies with Symptom Criteria Used with Implications for Epidemiological Studies: Role of Anthropometrics, Sleep Habit, and Comorbidities. Nat Sci Sleep 2022. PMID 35478719
Two features of the definition surprise people. First, it names no minutes. In a one-year study of 649 adults with DSM-5-based insomnia, 271 no longer met the criteria at follow-up, yet 66% of those 271 still reported at least 31 minutes of sleep-onset latency or wake time after falling asleep, and their daytime impairment was no different from people who still met criteria. The authors read this as tolerance of symptoms rather than normal sleep, and argued for adding quantitative cutoffs.
Pillai V, Roth T, Drake CL. Towards quantitative cutoffs for insomnia: how current diagnostic criteria mischaracterize remission. Sleep Med 2016. PMID 27288048
Second, nothing in the blood, the brain or a sleep lab confirms it. A 2026 overview in Nature Reviews Disease Primers puts the prevalence of insomnia disorder in adults at 10 to 16% and states that diagnosis relies on self-report, because a biomarker has not been established.
Spiegelhalder K, Baglioni C, Morin CM, et al. Insomnia disorder. Nat Rev Dis Primers 2026. PMID 41957444
Insomnia meaning in everyday speech and in medicine
The word comes from Latin: in- (not) and somnus (sleep). In everyday speech insomnia means any sleepless night or rough patch, and people say they had insomnia after a restless night before an exam. In medicine insomnia means something narrower and more lasting. The insomnia definition in the manuals therefore covers two different things: a symptom that nearly everybody has at some point, and a disorder that needs the full set of criteria.
The medical use changed between roughly 2005 and 2015. A 2015 overview in Nature Reviews Disease Primers describes a move from a purely symptom-based view towards recognizing insomnia as a disorder in its own right. It also notes that insomnia often appears together with other conditions such as pain and depression, rather than on its own.
Morin CM, Drake CL, Harvey AG, et al. Insomnia disorder. Nat Rev Dis Primers 2015. PMID 27189779
What are insomnia symptoms, at night and in the day?
The night-time symptoms are three patterns, and many people have more than one:
- Trouble falling asleep. You are in bed, tired, and sleep does not come.
- Trouble staying asleep. You wake during the night and find it hard to get back to sleep. The common version of this is waking at 3 a.m., covered in Why do I keep waking up at night?
- Waking too early. You wake well before you meant to and cannot go back to sleep.
The 2026 Nature Reviews overview lists fatigue, perceived impairments in cognitive functioning and mood disturbances as the common daytime symptoms. A JAMA review of adults adds irritability to the list. Those daytime effects carry weight in the definition. Someone who sleeps little, feels well and is not bothered does not have insomnia disorder.
Buysse DJ. Insomnia. JAMA 2013. PMID 23423416
Insomnia also keeps company with low mood. A review of more than 50 community surveys found that people with insomnia were more likely to have a major depressive episode, and longitudinal studies linked persistent insomnia to the appearance of a new depressive episode. That is an association seen in observation, not proof of cause, so waking at night with low mood is a reason to talk to a doctor rather than a verdict.
Types of insomnia: by duration, by pattern and by context
The ICSD-3 revised how insomnia is classified. The older long list of subtypes was folded into three groups: chronic insomnia disorder, short-term insomnia disorder and a residual group for other cases. The types people talk about in practice cut across those groups:
| Type | What defines it | Note |
|---|---|---|
| Short-term (acute) insomnia | Symptoms for less than three months | In one cohort, most spells resolved within days to weeks |
| Chronic insomnia | At least three nights a week for at least three months | Needs the daytime effect and sleep opportunity as well |
| Sleep-onset insomnia | Difficulty falling asleep | A pattern, not a separate diagnosis |
| Sleep-maintenance insomnia | Difficulty staying asleep | A pattern, not a separate diagnosis |
| Early-morning awakening | Waking earlier than wanted, unable to resume sleep | A pattern, not a separate diagnosis |
| Comorbid insomnia | Insomnia alongside pain, depression or another illness | Common; both conditions are assessed |
The first two rows are the formal split. The three pattern rows describe when in the night the trouble sits, and they overlap: a person can lie awake at the start of the night and wake early at the end. The comorbid row reflects the point from the 2015 overview that insomnia more often appears together with another condition than alone.
Acute vs chronic insomnia: what the long-term studies show
The boundary at three months is a convention, and it has moved: the 2008 guideline of the American Academy of Sleep Medicine called insomnia chronic after one month, an older criterion that ICSD-3 and DSM-5 replaced with three months. What happens before and after the line is measured in cohorts that follow people over time. One US study followed 1,248 good sleepers aged 35 and older for a year with daily sleep diaries. The one-year incidence of acute insomnia, defined as three or more nights a week for between 2 and 12 weeks, was 27.0%. Chronic insomnia developed in 1.8%. Of those who developed acute insomnia, 72.4% went on to recover good sleep and 19.3% kept sleeping poorly without meeting criteria for the chronic form.
Schutte-Rodin S, Broch L, Buysse D, et al. Clinical guideline for the evaluation and management of chronic insomnia in adults. J Clin Sleep Med 2008. PMID 18853708
Perlis ML, Vargas I, Ellis JG, et al. The Natural History of Insomnia: the incidence of acute insomnia and subsequent progression to chronic insomnia or recovery in good sleeper subjects. Sleep 2020. PMID 31848629
For people who already have insomnia the picture is less comforting. A Canadian cohort of 3,073 adults completed yearly surveys for five years. Among those who were good sleepers at the start, 13.9% developed an insomnia syndrome during the follow-up, and the rate was higher in women (17.6%) than in men (10.1%). Among those with insomnia at the start, 37.5% reported insomnia at every one of the five yearly assessments. Remission was slower for the full syndrome than for milder, subsyndromal insomnia: at 5 years 40.9% of the syndrome group had remitted against 73.6% of the subsyndromal group. The authors concluded that insomnia is often a persistent condition.
Morin CM, Jarrin DC, Ivers H, et al. Incidence, Persistence, and Remission Rates of Insomnia Over 5 Years. JAMA Netw Open 2020. PMID 33156345
Read together, the two studies describe a common, usually self-limiting acute form and a smaller but sticky chronic form. They are observational: they show what happened to people, not why.
How common is insomnia?
The number depends on which definition is counted. A review of more than 50 community surveys sorted the estimates into four definitions, from any single symptom to a formal diagnosis. Later surveys show how much the wording of the criteria moves the figure.
| Definition or source | Share of adults | What was counted |
|---|---|---|
| At least one insomnia symptom | About one in three | Review of more than 50 community surveys |
| Symptoms plus daytime consequences | 9 to 15% | Same review |
| Diagnosis by DSM-IV criteria | About 6% | Same review |
| Insomnia disorder, recent overview | 10 to 16% | Nature Reviews Disease Primers, 2026 |
| DSM-IV-TR versus ICD-10 criteria | 22.1% versus 3.9% | America Insomnia Survey, 10,094 health plan members |
| ICSD-3-style criteria, online survey | 23.2%, against 7.5% ever diagnosed | 2,044 Australian adults |
Ohayon MM. Epidemiology of insomnia: what we know and what we still need to learn. Sleep Med Rev 2002. PMID 12531146
Roth T, Coulouvrat C, Hajak G, et al. Prevalence and perceived health associated with insomnia based on DSM-IV-TR; International Statistical Classification of Diseases and Related Health Problems, Tenth Revision; and Research Diagnostic Criteria/International Classification of Sleep Disorders, Second Edition criteria: results from the America Insomnia Survey. Biol Psychiatry 2011. PMID 21195389
The American survey found that the stricter ICD-10 definition missed most of the health burden: 66% of the population-level loss of perceived health attributed to insomnia, and 84% of clinically relevant cases, fell outside it. A JAMA review gives a prevalence of insomnia disorder of approximately 10 to 20%, with about half following a chronic course. All of these are survey estimates. They describe how many people say they meet a definition, not how many have been diagnosed. The Australian survey shows the gap: its estimate was three times the share who reported ever being diagnosed.
Women report insomnia more often than men in every definition of the review. The prevalence of symptoms generally rises with age, while the rates of dissatisfaction with sleep and of diagnosis vary little.
Insomnia or sleep deprivation?
Both leave you tired, which is why they get mixed up. The difference is the opportunity criterion in the table above. Sleep deprivation is a shortage of time: a late bedtime, a night shift, a baby that wakes. Insomnia is a shortage of sleep despite the time. The easiest check is what happens when you are given the chance:
| Question | Short of sleep | Insomnia |
|---|---|---|
| Time in bed | Too short for what you need | Enough, often generous |
| When the chance comes | You fall asleep quickly, often at once | You lie awake or wake again |
| What fixes it | More time for sleep | Time alone does not fix it |
| Daytime effect | Tiredness that eases after catching up | Tiredness and strain that persist |
People can have both, and an unsuitable setting (noise, light, a snoring partner) blurs the picture. The effects of too little sleep are described in Sleep deprivation symptoms. Other sleep disorders can also look like insomnia from the inside. Sleep apnea and periodic limb movements are the examples the European guideline gives as reasons for a sleep study, and they are listed with the rest in Sleep disorders and insomnia.
Insomnia diagnosis criteria in practice: the interview, the diary, the exceptions
Applying the insomnia diagnosis criteria is a conversation, not a machine reading. The 2023 European Insomnia Guideline recommends a clinical interview covering sleep and medical history, plus sleep questionnaires and diaries, and a physical examination or extra measures where indicated. Actigraphy, a wrist device that infers sleep from movement, is not recommended for routine evaluation but may help tell conditions apart. Overnight polysomnography is advised when another sleep disorder is suspected, for example periodic limb movements or a sleep-related breathing disorder, for insomnia that has not responded to treatment, and for other indications the guideline lists.
Riemann D, Espie CA, Altena E, et al. The European Insomnia Guideline: An update on the diagnosis and treatment of insomnia 2023. J Sleep Res 2023. PMID 38016484
The same JAMA review says the diagnosis rests on a thorough history of sleep behaviors, medical and psychiatric problems and medications, supplemented by a prospective sleep diary, and that a thorough clinical history is often sufficient to identify the factors that contribute to insomnia. A diary is simple: for one or two weeks, write down when you went to bed, how long you think it took to fall asleep, how often you woke and when you got up. It is the document a clinician will ask for, and it is what the insomnia test page walks through.
When to see a doctor about insomnia
The guidelines frame insomnia as a condition to assess when it is persistent and affects the day. The European guideline recommends cognitive behavioral therapy for insomnia (CBT-I) as first-line treatment for chronic insomnia in adults of any age, in person or digitally, and the same line appears in the 2026 overview. What a course contains is explained in CBT for insomnia explained.
The situations in which a medical look is the sensible next step, rather than waiting, are the ones that overlap with other conditions:
- Trouble sleeping for several weeks that leaves you sleepy at work or behind the wheel.
- Low mood, loss of interest or dread that comes with the sleeplessness.
- Loud snoring, with pauses in breathing seen by a partner. This pattern points towards sleep apnea, which can sit behind what feels like insomnia.
- Sleeplessness that started after a new medicine, or that comes with pain or breathing problems at night.
What SleepTrace can show for a doctor's visit
Insomnia is diagnosed from what you report, so no recording can confirm it or rule it out. SleepTrace listens through the microphone of your iPhone or Android phone, sound only, and it can add a few facts to a diary. It estimates your sleep phases from sound (an estimate, not a sleep study), saves playable clips of snoring, talking and coughing with a dB peak and a time (3 clips a month on the free plan), and marks possible breathing pauses with a timestamp, without a clip. Those details show what was audible near a waking, such as snoring, talking, coughing or a possible breathing pause, and when. They do not show why you woke, and a quiet waking leaves no event in the record.
It does not measure movement, it cannot tell how long you were trying to fall asleep, and its sleep apnea indicator is a screening estimate, not a diagnosis. Keep the app open (the screen dims by itself) and the phone on its charger.
Frequently asked questions
Insomnia is repeated trouble falling asleep, staying asleep or waking too early although you have the time and a suitable place to sleep, together with daytime problems such as fatigue, poor concentration or low mood. One bad night does not qualify. For chronic insomnia disorder the trouble has to occur at least three times a week and last at least three months.
In everyday speech people call any sleepless night insomnia. In medicine the word is narrower: a persistent sleep complaint with daytime consequences. In a one-year diary study of 1,248 good sleepers, 27.0% had a spell of acute insomnia, defined as three or more nights a week for 2 to 12 weeks, and 72.4% of those recovered good sleep, so short spells are common and usually pass.
At night: difficulty falling asleep, difficulty staying asleep and waking earlier than wanted. In the day: fatigue, perceived problems with concentration and memory, and mood changes. Insomnia disorder needs both the night-time complaint and a daytime effect, and the person has to have enough opportunity to sleep. No test or biomarker confirms it, so the diagnosis rests on what you report.
Duration. Acute or short-term insomnia lasts less than three months. Chronic insomnia disorder means the trouble occurs at least three nights a week for at least three months (the 2008 AASM guideline used one month, an older criterion). In a Canadian cohort of 3,073 adults followed for five years, 37.5% of those with insomnia at the start still had it at all five yearly check-ins.
By a clinical interview about sleep and medical history, usually with sleep questionnaires and a sleep diary kept for a week or two. The European guideline does not recommend actigraphy for routine evaluation and advises overnight polysomnography when another sleep disorder such as sleep apnea is suspected, for insomnia that does not respond to treatment and for other indications it lists.
No. Sleep deprivation means too little time allowed for sleep, for example because of a late bedtime, shift work or a baby. Insomnia means the trouble persists although the opportunity is there. The two can overlap, and a person can have both, which is one reason a clinician asks about your schedule before anything else.
SleepTrace is a wellness app, not a medical device. This article is general information, not medical advice. If your symptoms are frequent, severe or worrying, please talk to a doctor.
The definition turns on how you feel and function, which no recording can measure. SleepTrace records sound only: it estimates your sleep phases, saves clips of snoring, talking and coughing with a dB peak and a time, and timestamps possible breathing pauses. That shows what was audible near a waking, not why you woke. It cannot diagnose insomnia; tracking is free, with 3 playable clips a month.
Hear your own night. SleepTrace turns a night of audio into your sleep phases, the sounds you made, and how it all trends. Works without a wearable, better with one. Your phone on the nightstand is enough to start. Get it for iPhone or Android →