Migraines are thought to be caused by changes in the chemicals of the brain.
In particular, levels of a type of chemical called serotonin decrease during a migraine.
Low levels of serotonin can make the blood vessels in a part of your brain spasm (suddenly contract), which makes them narrower. This may cause the symptoms of aura. Soon after, the blood vessels dilate (widen), which is thought to cause the headache. The reason for the drop in serotonin is not yet fully understood.
Hormones
Some scientists believe that fluctuating levels of hormones are closely linked to the cause of migraines.
Some women who experience migraines say they are more likely to have an attack around the time of their period. This is known as a menstrual migraine. Just before women have their period, levels of the hormone oestrogen fall.
Women can have menstrual migraines from two days before to three days after the first day of their period. About 1 in 7 women who have migraines only have an attack around the time of their period. This is known as a pure menstrual migraine. Around 6 in 10 women with migraines have attacks at other times too.
Other migraine triggers
Many factors have been identified as triggers for a migraine. These triggers include emotional, physical, dietary, environmental and medicinal factors. They are outlined below.
Emotional triggers
These include:
- stress
- anxiety
- tension
- shock
- depression
- excitement
Physical triggers
Physical triggers include:
- tiredness
- poor quality of sleep
- shift work
- poor posture
- neck or shoulder tension
- travelling for a long period of time
- low blood sugar
The menopause can also trigger migraines.
Dietary triggers
Dietary triggers include:
- lack of food (dieting)
- delayed or irregular meals (see below)
- dehydration
- alcohol
- the food additive tyramine
- caffeine products, such as tea and coffee
- specific foods such as chocolate, citrus fruit and cheese
When you do not eat regular meals, your blood sugar levels fall. If you then eat a sugary snack, blood sugar levels shoot up. These ‘peaks and troughs' could trigger migraine attacks.
Environmental triggers
Environmental triggers include:
- 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
Medicines
Some medicines can trigger migraines, including:
- some types of sleeping tablets
- the contraceptive pill
- hormone replacement therapy (HRT), which is sometimes used to treat the menopause
