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ReSomnia

Guide · 7-minute read

What causes insomnia: why we sleep badly, and why it lasts

Insomnia rarely has a single cause. It usually arises when a vulnerability meets a trigger (stress, illness, a bereavement), and is then kept going by habits or thoughts, even after the event has passed[1]. The good news: these maintaining factors are precisely the ones you can do something about[3].

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By Andy Leleux, sleep technologist · Updated on 27 October 2026

Key points

  • Three types of factors: what makes you vulnerable, what sets insomnia off, what keeps it going[1].
  • Insomnia that lasts is often sustained by compensating habits and by a body and mind on high alert[1][2].
  • Women are affected more often, and the risk rises with age and around the menopause[4][5][6].
  • Coffee, alcohol and screens can make sleep worse, but their role as causes in their own right is less well established.

Rarely a single cause: the three types of factors

The most widely used model for understanding insomnia, put forward by Spielman in 1987, separates three types of factors, which add up[1]:

  • What makes you vulnerable (predisposing factors): being a woman, age, an anxious temperament or a tendency to ruminate, past insomnia, sleep that is particularly sensitive to stress.
  • What sets it off (precipitating factors): stress at work or at home, a bereavement, illness, pain, a hospital stay, the menopause, a change in your schedule.
  • What keeps it going (perpetuating factors): spending more time in bed to compensate, napping, getting up at irregular times, checking the clock at night, lying awake in bed, worrying about sleep, having a late coffee to keep going.

The trigger often explains the first bad nights. But if insomnia lasts for months, it is mostly the maintaining factors that sustain it[1].

Hyperarousal: a body and mind stuck on alert

Researchers describe a state of hyperarousal in many people with insomnia, by day as well as by night: racing thoughts, difficulty switching off from your worries, and signs that the body is activated (heart rate, stress hormones, fast brain activity during sleep)[2].

This is an explanatory model, not a lab test: not everyone shows the same signs. Its main value is in helping you understand why trying to sleep at all costs so often has the opposite effect.

The main risk factors

  • Being a woman: a meta-analysis covering more than a million people found the risk of insomnia to be 1.4 times higher in women than in men, and the gap widens with age[4].
  • The menopause: sleep problems are common during and after the transition, including in women without hot flushes[6]. See insomnia in women.
  • Age: insomnia symptoms become more common as we get older[5].
  • Depression and anxiety: these and insomnia often feed each other. Persistent insomnia is associated with the onset of depressive episodes[5].
  • Chronic pain and illness: these disturb sleep, and lack of sleep makes pain harder to bear.
  • Night work and irregular hours: these put your body clock out of step; the European guideline advises checking for them routinely[3]. See insomnia and night shifts.

Coffee, alcohol, screens: what we really know

A coffee late in the day, a drink in the evening or late-night screens can delay sleep or make it lighter. But the studies do not allow us to say that they cause chronic insomnia on their own: their effect is tangled up with stress, schedules and habits. Noting them in a sleep diary (before and after 2 pm, for example) helps you see what matters for you.

When it is not (only) insomnia

Other sleep disorders or health problems can lie behind bad nights: sleep apnoea, restless legs syndrome, a shifted body clock, but also depression, an overactive thyroid or certain medicines. The European guideline stresses the importance of looking for them[3]. The signs to know about are set out in Do I have insomnia?.

How many people are affected?

It all depends on what is being measured. According to a review of more than 50 population studies, about one adult in three has at least one insomnia symptom, 9 to 15% have symptoms with daytime consequences, and about 6% meet the criteria for a diagnosis of insomnia[5].

What you can change

You cannot choose your age or your genes, and you cannot always control what life throws at you. But the maintaining factors (time spent in bed, your schedule, your thoughts about sleep) can be worked on: they are exactly what CBT-I targets, and CBT-I is the treatment recommended first for chronic insomnia[3].

  • Sleep restriction reduces the time you spend awake in bed.
  • Stimulus control links your bed with sleep again.
  • A sleep diary helps you spot your own factors: schedule, naps, coffee, alcohol.

Frequently asked questions

Can stress cause chronic insomnia?

Stress often sets off the first bad nights. Insomnia becomes chronic when compensating habits and worry about sleep take over, even once the stress has passed. See our guide Insomnia and stress.

Why does my insomnia continue when the problem has been sorted out?

Because it is no longer the same factors keeping it going: time spent in bed, irregular hours, naps, a bed linked with being awake, fear of sleeping badly. These are what CBT-I works on.

Can coffee cause insomnia?

A late coffee can delay sleep, especially in people who are sensitive to it. But it is rarely the only cause of chronic insomnia. Noting your cups before and after 2 pm in your diary helps you see whether it matters in your case.

Is insomnia hereditary?

Some people do have a family vulnerability, but that is not enough to cause insomnia: it also takes a trigger and factors that keep it going.

Do screens stop you sleeping?

Screens in the evening can push back your bedtime and keep your mind alert. Their role as a direct cause of chronic insomnia is less well established than that of sleep habits.

Read and do next

Sources

  1. [1] Spielman AJ, Caruso LS, Glovinsky PB. A behavioral perspective on insomnia treatment. Psychiatr Clin North Am. 1987;10(4):541-553. PubMed
  2. [2] Riemann D, et al. The hyperarousal model of insomnia: a review of the concept and its evidence. Sleep Med Rev. 2010;14(1):19-31. PubMed
  3. [3] Riemann D, et al. The European Insomnia Guideline: an update on the diagnosis and treatment of insomnia 2023. J Sleep Res. 2023;32(6):e14035. PubMed
  4. [4] Zhang B, Wing YK. Sex differences in insomnia: a meta-analysis. Sleep. 2006;29(1):85-93. PubMed
  5. [5] Ohayon MM. Epidemiology of insomnia: what we know and what we still need to learn. Sleep Med Rev. 2002;6(2):97-111. PubMed
  6. [6] Soares CN, et al. Impact of sleep disturbances on health-related quality of life in postmenopausal women: a systematic review. Menopause. 2026;33(1):118-128. PubMed

This guide provides information and does not replace advice from a doctor or psychologist. If you are in distress, call your local crisis line at any hour: 1813 or 0800 32 123 in Belgium, 116 123 in the UK and Ireland, 988 in the US. In immediate danger, call 112 in Europe or your local emergency number.

Find out what is keeping your difficult nights going.

Every morning, the ReSomnia diary records your sleep times, your naps, and your coffee and alcohol before and after 2 pm. The CBT-I programme then works on what keeps insomnia going. Free.

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The app itself is in French for now. English is on the way.