The exact cause of migraines is unknown, although they are thought to be the result of abnormal brain activity temporarily affecting nerve signals, chemicals and blood vessels in the brain.

It's not clear what causes this change in brain activity, but it is possible that your genes make you more likely to experience migraines as a result of a specific trigger.

Migraine triggers

Many possible migraine triggers have been suggested, including hormonal, emotional, physical, dietary, environmental and medicinal factors.

Hormonal changes

Some women experience migraines around the time of their period, possibly because of changes in the levels of hormones such as oestrogen around this time.

These are known as menstrual-related migraines and they usually occur between two days before the start of your period to three days after. Some women only experience migraines around this time, but most experience them at other times too.

Many women find their migraines improve after the menopause, although the menopause can trigger migraines or make them worse in some women.

Emotional triggers:

• stress
• anxiety
• tension
• shock
• depression
• excitement

Physical triggers:

• tiredness
• poor quality sleep
• shift work
• poor posture
• neck or shoulder tension
• jet lag
• low blood sugar (hypoglycaemia)
• strenuous exercise, if you are not used to it

Dietary triggers:

• missed, delayed or irregular meals
• dehydration
• alcohol
• the food additive tyramine
• caffeine products, such as tea and coffee
• specific foods such as chocolate, citrus fruit and cheese

Environmental triggers:

• bright lights
• flickering screens, such as a television or computer screen
• smoking (or smoky rooms)
• loud noises
• changes in climate, such as changes in humidity or very cold temperatures
• strong smells
• a stuffy atmosphere

Medication:

• some types of sleeping tablets
• the combined contraceptive pill
• hormone replacement therapy (HRT), which is sometimes used to relieve symptoms associated with the menopause