One reason we often say 'It's a real headache' if we have a stressful situation is that stress and anxiety do often bring on headaches. Worry, anger and general feelings of unease are a major cause, but there are many others.

Our physical surroundings and actions can also play a role: many people get headaches if the light is too bright, or if their environment is too hot or cold. There are also a lot of allergic reactions that can cause headaches; it's quite common for someone to get this reaction to a cleaning product or perfume, for example, though it can be very difficult to pin down exactly which product is causing the problem.

Another trigger is food. It's quite well known that too much caffeine or chocolate can trigger headaches even in people who don't normally have a problem, while migraine sufferers often have to avoid certain foods altogether.

You can find a list of the most common causes, and how to deal with them, here.