It's 3am and you're wide awake. At least you can be reassured that, like you, millions of other people are lying in bed, staring into the dark. A study by the Sleep Centre in Edinburgh says January is the most sleepless month of the year. The same research has named 3am as Anxiety Hour, when up to 8.5 million adults are regularly jolted awake. Worries over money (particularly after an expensive Christmas), family and work are the insomniac's favourite mental torture topics.

Our inability to get a good night's rest is also largely to do with too much darkness, which confuses our internal clock. "We fall asleep because our bodies have a pressure to sleep, but this wears off after three or four hours," says Dr Chris Idzikowski, director of the Sleep Centre. "But there is a second factor - our internal clock - which tells us it's good to keep sleeping. Our internal clock is largely synchronised by light so when there is a lot of darkness at this time of year, the internal clock drifts. We sleep much better if we are exposed to bright sunshine followed by a rapid descent into darkness."

Then there is the problem of noise. The UK Noise Association says our cities are 10 times noisier than they were a decade ago, especially at night, and this year, a mild winter has brought unseasonably loud early birdsong.

"We have had an influx of calls about robins singing at night in particular," says Grahame Madge of the RSPB. "Because the winter has been so mild, there's plenty of food around and they are getting into breeding conditions earlier. A number of other birds have been in song, such as song thrushes and house sparrows. You would expect it to start in February, and Easter is the main nesting time. Still, I'm thankful we can still hear birds singing, even if it does wake me up."