Insomnia: recognising it, why it happens, and how it is treated

What insomnia is, and what it is not

Most people who start reading about insomnia start from a number: I only sleep five hours. But the diagnostic criteria do not use hours of sleep, and the reason is practical. Sleep need varies a great deal between people, and human beings are rather poor at estimating their own sleep.

Instead, insomnia disorder is defined by a combination. There must be a night-time symptom: trouble falling asleep, trouble staying asleep, or waking earlier than intended. There must be a daytime consequence: fatigue, poor concentration, irritability, reduced performance, or worry about sleep itself. It must be frequent enough, from three nights a week. And it must happen even though you genuinely had the chance to sleep.

Short-term and chronic

Why insomnia feeds itself

This explains why "treating the original cause" is often not enough. After a bad patch of sleep, people respond very naturally: they go to bed earlier to give themselves more chance, they linger in the morning, they nap, and they monitor their sleep closely. Each response makes sense. All of them make the problem worse.

1. More time in bed dilutes sleep pressure. Sleep pressure builds with hours spent awake; hours spent lying awake in bed build nothing.
2. A shifting wake time blurs the circadian signal, so the body no longer knows when it should feel sleepy.
3. The bed gradually becomes a cue for wakefulness rather than for sleep. This is learned association, and it can be unlearned.
4. Worrying about not sleeping raises arousal, and high arousal is precisely what prevents sleep.

Those four mechanisms are why behavioural therapy works: it does not try to make you sleepier, it dismantles the things keeping you awake.

Seven groups of causes to review

• Psychological - stress, anxiety, depression. The largest group, and the relationship with insomnia runs both ways.
• Other sleep disorders - sleep apnoea, restless legs syndrome, circadian rhythm disorders.
• Physical illness - chronic pain, reflux, nocturia, lung disease, thyroid disease, the menopausal transition.
• Medication and substances - many common medicines disturb sleep; caffeine, alcohol and nicotine all matter.
• Behaviour - irregular timing, long daytime naps, using the bed for other activities.
• Environment - light, noise, room temperature, a snoring bed partner.
• Circadian rhythm - night shifts, jet lag, a naturally late chronotype.

How it is treated

For chronic insomnia, international guidelines agree on placing cognitive behavioural therapy first line. The notable word in that recommendation is "first": it does not say try medication and use therapy when medication fails.

The reason lies in what happens after treatment stops. Medication works from the first night, but symptoms usually return when it is withdrawn. Behavioural therapy takes several weeks to show its effect, and that effect usually persists after the course ends, because what changed was the mechanism rather than an ongoing chemical effect.