Maybe. Although most people have difficulty dropping off every so often, an estimated one in 10 suffers insomnia on a regular basis.

What is it caused by?

Stress is the most common trigger, but shift work, depression, flying across time zones, a poor sleeping environment and physical illness can be major causes.

How much sleep should I be getting?

Margaret Thatcher famously boasted that she could run the country on less than five hours a night, but most scientists agree that the average adult needs seven to eight hours.

What should I do?

Sort out the root cause, then stick to a routine, exercise often and ensure that your bedroom is dark, quiet and at the right temperature.

What shouldn't I do?

Avoid large meals late in the evening, as well as stimulants such as coffee.