Feeling exhausted by day and then being unable to sleep at night is a form of torture familiar to teachers. Long before Ofsted came along to induce performance anxiety, they used to lie awake at night worrying about their pupils’ welfare. It’s that sort of job.

But that doesn’t make insomnia easier to live with. Inadequate sleep impairs concentration and memory, and causes irritability, tiredness and anxiety. Sufferers describe a feeling of mounting panic: they know they aren’t coping well because they are worn out, but can’t get the sleep they need to cure the tiredness.

Short-term or “transient” insomnia usually has an identifiable cause - impending inspection, for example, or emotional trauma - and passes when the anxiety subsides. Long-term or “chronic” insomnia is harder to tackle. Sufferers may have difficulty falling asleep or may fall asleep quickly, but lie awake for hours during the night. It may have underlying physiological or psychological causes that can be treated (for example, it is sometimes a symptom of depression). But the main problem is that chronic insomniacs know they respond to anxiety by lying awake at night - and this in itself becomes a source of stress.

To cure themselves, they must learn to overcome not just sleeplessness, but the fear of sleeplessness. An obvious step is to avoid stimulants such as coffee and energetic exercise in the evening. Folk remedies include eating a lettuce leaf before bed, keeping a cut-up onion in a jar by the bed an sniffing it; eating a sugary or starchy snack at night or having a source of low noise, such as a fan in the room. The herb valerian, available as tablets or teabags, is a well-known soporific. The homoeopathic remedy arnica is useful when you are overtired, but too restless to sleep. Prescription sleeping tablets are addictive, so should only be used as a short-term measure.

“Bright light” therapy is based on the theory that insomniacs have confused body clocks. If you have difficulty falling asleep at night, try to get bright light in the morning. If you wake up too early, get bright light in the evening. Relaxation routines, in which you systematically relax muscle groups while breathing rhythmically, can be effective.

Paradoxically, some insomniacs spend too much time trying to sleep. You should fall asleep within 20 minutes of switching off the light. If, after half an hour, you are still awake and feeling anxious, get up and do something else until you feel sleepy. If you are sleepless during the night, get up and have a drink (of warm milk or herbal tea), run a bath, read or listen to the radio, then go back to bed when you feel tired. Try to condition your body to respond to bed as a place where you relax, not as a place where you worry.

As a last resort, convince yourself that getting by on little sleep is a sign of evolutionary superiority. Leonardo da Vinci is said to have trained himself to sleep for 15 minutes every four hours, leaving 22-and-a-half hours of every day free for productive activity.