What is it?

We've all been there - that horrible feeling when you're tossing and turning instead of sleeping.  Luckily, for most of us, it's just the odd night.  But for one in five people in Britain, it happens all the time.  The condition is said to be chronic if it lasts for more more than three weeks.  For severe insomniacs, lack of sleep controls almost every aspect of their lives, from relationships to work.  Professor Colin Espie, of Glasgow University, who runs a sleep clinic for insomniacs, says that, in most cases, there is an underlying cause, such as stress, depression or anxiety.   Sometimes, a change in the person's life can be the trigger.  Professor Espie recommends keeping a sleep diary to log your sleep patterns.  That'll help you to begin to understand the problem, trace any triggers, and let you see if changes you make are doing any good.

Why do we need sleep?

There are lot's of theories, but no-one is really sure why we need sleep.  Boffins think dreaming may be the brain's way of replaying experiences and lessons we've learned so that they are fixed in the memory for later use.  One thing's certain, we need sleep more than we need food.  We can survive for up to two months without food - we can't survive for more than seven to ten days without sleep!  Losing just one or two hours sleep can result in impaired concentration and an increased appetite - people will eat more to keep themselves awake.  Miss three or four hours sleep and irritation will kick in, along with pressure to catnap, particularly around lunchtime.  You'll be moody, and won't be able to focus on work.  After five or six hours lost sleep, everything will be a struggle and you'll feel very low.  The body's - and the mind's - defences will be down, you'll feel ultra-sensative and be prone to over-react to everyday situations.

What causes insomnia?

People who find it hard to drift off usually don't have enough serotonin, which helps make melatonin - the hormone that controles when you sleep and when you don't.  To boost levels of serotonin, eat lot's of vitamin B6, which can be found in carrots, cheese, avocados, lentils, peas spinach and potatoes.  A physical cause in women can be the drop in progesterone levels in the body which occurs towards the end of a period - some women have problems falling asleep around this time.

Ways to tackle it