What Is Insomnia?

Intro

Insomnia is the most common sleep disorder. It affects an estimated 10–15% of adults as a chronic condition and up to 30–40% of the general population in milder or transient forms. Yet it is consistently under-treated — most people either normalise it, self-medicate with alcohol, or manage it with over-the-counter sedatives, none of which address the underlying problem.

← Back to Sleep Health Hub

Key Points

Insomnia is difficulty falling asleep, staying asleep, or waking too early on at least 3 nights per week — with daytime consequences such as fatigue, mood disturbance, or impaired concentration.
Acute insomnia (less than 3 months) is usually triggered by a specific stressor and often resolves when it passes.
Chronic insomnia (3 months or more) is maintained by conditioned arousal and maladaptive behaviours — independent of the original trigger.
CBT-I is the first-line treatment per international guidelines — more effective long term than any sleeping pill.
Insomnia frequently co-occurs with depression, anxiety, and chronic pain — these relationships are bidirectional.

What Insomnia Is — and Is Not

Clinical insomnia requires three components:

A sleep complaint — difficulty initiating sleep, maintaining sleep, or waking earlier than desired
Adequate opportunity for sleep — the problem is not simply insufficient time in bed
Daytime impairment — fatigue, mood disturbance, concentration problems, reduced performance, or increased errors or accidents

Insomnia should be distinguished from:

Normal sleep variation — sleeping slightly less than average without any daytime impairment
Insufficient sleep syndrome — sleeping too little by choice rather than inability
Circadian rhythm disorders — delayed sleep phase (unable to sleep until very late) or advanced sleep phase (waking extremely early); these involve timing, not the ability to sleep
Other sleep disorders — sleep apnoea and restless legs syndrome can both fragment sleep but require different evaluation and treatment

Acute vs Chronic Insomnia

Acute insomnia (also called short-term or adjustment insomnia):

Duration: less than 3 months
Usually triggered by an identifiable cause: stress, illness, jet lag, shift change, or environmental disruption
Often resolves when the trigger resolves
Risk of becoming chronic if perpetuating behaviours develop

Chronic insomnia:

Duration: 3 months or more, at least 3 nights per week
Often started with an acute trigger but is now maintained by conditioned arousal — the brain has learnt to associate the bedroom with wakefulness and anxiety
The original trigger may long since have passed
The perpetuating behaviours — lying in bed awake for hours, irregular schedules, excessive time in bed, pre-sleep anxiety — maintain the disorder in a self-reinforcing cycle

Causes and Contributing Factors

Insomnia is best understood using the 3P model:

Predisposing factors — make you vulnerable:

Trait anxiety or worry-prone thinking style
Genetic sleep architecture (lighter sleepers)
Female sex (insomnia is approximately twice as common in women)
Older age
Personal or family history of mood disorders

Precipitating factors — trigger the episode:

Acute stress: work pressure, relationship breakdown, bereavement
Medical events: illness, surgery, pain
Psychiatric events: depressive episode, anxiety disorder onset
Life changes: new baby, shift change, moving home
Medications: stimulants, corticosteroids, some antidepressants

Perpetuating factors — maintain the disorder:

Spending excessive time in bed trying to catch up on sleep
Inconsistent sleep and wake times
Daytime napping
Using the bedroom for activities other than sleep and sex
Catastrophic thinking about sleep (“I’ll never function tomorrow”)
Checking the clock repeatedly during the night
Using alcohol as a sleep aid

Symptoms

Night-time symptoms:

Lying awake for 30 minutes or more before falling asleep
Waking frequently during the night and finding it difficult to return to sleep
Waking substantially earlier than desired and being unable to fall back asleep
Sleep that feels light, unrefreshing, or non-restorative despite adequate time in bed

Daytime consequences:

Fatigue and low energy
Difficulty concentrating or remembering
Mood disturbance — irritability, low mood, anxiety
Reduced performance at work or school
Increased errors or safety concerns
Social withdrawal or reduced enjoyment of activities
Preoccupation or hypervigilance about sleep

Common Co-occurring Conditions

Insomnia rarely exists in isolation:

Depression: Insomnia is both a symptom of depression and an independent risk factor for developing it. The relationship is bidirectional — treating either condition partially improves the other.
Anxiety: Anxiety disorders are among the strongest correlates of chronic insomnia. Hyperarousal at bedtime drives both conditions.
Sleep apnoea: OSA fragments sleep and causes non-restorative sleep; it can present as or worsen insomnia. The two conditions frequently coexist. CBT-I remains effective in the context of treated OSA.
Chronic pain: Pain disrupts sleep architecture and insomnia lowers pain thresholds — a reinforcing cycle.
Menopause: Night sweats and hormonal shifts make insomnia extremely common during the menopausal transition. See Menopause.

Diagnosis

Insomnia is a clinical diagnosis — no blood test or imaging is required. A clinician will typically:

Take a sleep history: pattern, duration, daytime impact, precipitating and perpetuating factors
Assess for co-occurring conditions: depression, anxiety, sleep apnoea, restless legs, pain, medications
Review a sleep diary — a 1–2 week log of bed time, wake time, estimated sleep duration, and quality
Consider standardised questionnaires such as the Insomnia Severity Index (ISI) or Pittsburgh Sleep Quality Index (PSQI)
Order a sleep study only if a co-occurring sleep disorder such as OSA or periodic limb movement disorder is suspected

Treatment

First line: CBT-I

Cognitive behavioural therapy for insomnia (CBT-I) is the first-line treatment recommended by the American College of Physicians, the British Association for Psychopharmacology, and the European Sleep Research Society.

It combines:

Sleep restriction — consolidating time in bed to build sleep pressure
Stimulus control — rebuilding the bed as a sleep cue only
Cognitive restructuring — challenging catastrophic sleep beliefs
Relaxation training — reducing physiological arousal at bedtime
Sleep hygiene — optimising behaviour and environment

A full course runs 6–8 sessions. Improvements typically begin within 2–3 weeks and are sustained at 12-month follow-up. Digital CBT-I programmes have comparable efficacy for many patients.

Sleep hygiene

Sleep hygiene — consistent schedules, morning light, screen curfew, bedroom environment — is necessary but not sufficient for chronic insomnia. It is foundational and should accompany all other treatment.

Medication

Medications are not a first-line treatment for chronic insomnia. Short-term use may be appropriate when sleep deprivation is acutely impairing safety, CBT-I is not yet accessible, or an underlying condition is being treated. All sedative-hypnotics carry risks of tolerance, dependence, and rebound insomnia with prolonged use. Discuss options and duration with a prescriber.

Melatonin has a role in circadian-related sleep difficulty (delayed sleep phase, jet lag, shift work) but limited evidence for treating chronic insomnia.

When to Seek Help

See a doctor if:

Difficulty sleeping has persisted for more than 3 months
Sleep problems occur at least 3 nights per week
Daytime impairment is affecting work, relationships, or safety
You are relying on alcohol or sedatives to sleep
You suspect sleep apnoea — snoring, witnessed breathing pauses, gasping, or excessive daytime sleepiness despite time in bed
Low mood, anxiety, or other mental health symptoms accompany the sleep problem

See When to Seek Help for Insomnia for a detailed decision guide.

FAQ

Q: What is insomnia?
A: A sleep disorder characterised by difficulty falling asleep, staying asleep, or waking too early on at least 3 nights per week, with daytime consequences including fatigue, mood disturbance, or impaired concentration.

Q: What is the difference between acute and chronic insomnia?
A: Acute insomnia lasts days to weeks and is usually triggered by an identifiable stressor. Chronic insomnia persists for 3 months or more and is often maintained by conditioned arousal and maladaptive behaviours, even after the original trigger has resolved.

Q: What causes chronic insomnia?
A: The 3P model: predisposing vulnerability, a precipitating event, and perpetuating behaviours — irregular schedules, excessive time in bed, catastrophic thinking about sleep — that maintain the disorder long after the trigger has passed.

Q: How is insomnia treated?
A: CBT-I is the first-line treatment per international guidelines. It addresses the behavioural and cognitive factors that perpetuate insomnia. Sleep hygiene and short-term medication may also have a role.

Q: Can insomnia go away on its own?
A: Acute insomnia often resolves once the trigger passes. Chronic insomnia is less likely to resolve without intervention because the perpetuating cycle tends to be self-reinforcing.