Migraine Headaches: Causes vs. Triggers

The underlying cause of a migraine headache is sometimes confused with the migraine’s triggers. The underlying cause refers to the process in the body producing migraine symptoms. In contrast, triggers are external factors that may set off a migraine headache episode in an individual. Below are examples of each.

Causes of Migraine Headaches

The exact mechanism causing migraine headaches is unclear, and many theories have been suggested with varying amounts of data supporting each of them:

  • Constriction of the blood vessels, also called vasoconstriction, followed by blood vessel dilation in the blood vessels and arteries supplying the brain, is the oldest theory of how migraines are caused.
  • Inflammation in the brain from cortical depression is another potential cause. Cortical depression occurs when the blood flow in the brain increases, then declines, causing nerve cell depression and leading to migraine pain.
  • Inappropriate secretion of hormones and neurotransmitters, such as dopamine and serotonin, can cause blood vessels to constrict or dilate.
  • A dysfunction of the smooth muscle lining of blood vessels can cause pain. The smooth muscles regulate contraction and dilation of the blood vessels.
  • Abnormal levels of estrogen (in women) affect brain chemicals, leading to pain. There is evidence that genetics also plays a role.

Migraines frequently run in families, and one research study found a genetic mutation that appears to raise the susceptibility to migraine headaches.1


Common Migraine Triggers

While not all migraines have a clear trigger, certain actions or substances may make a migraine more likely. These are several common migraine triggers:

  • Stress. Nervousness or tension—as may occur during an especially hectic day at work—can increase the risk of a migraine headache. In some cases, a drop in stress levels during a weekend or on vacation can also increase the risk.
  • Varied schedules. Skipping meals or altering sleep schedules adds to the risk of migraines in many cases. Keeping a similar eating and sleep schedule during the weekends and weekdays may help avoid migraines.
  • Exposure to scents. Being around strong perfume or cigarette smoke can cause a migraine.
  • Foods. Among the more common problem food triggers of migraines are dairy products; food additives, such as the sweetener aspartame; the flavor enhancer monosodium glutamate (MSG); eggs; chocolate; and red wine.
  • Changes in weather. Increases in outdoor temperature can trigger migraines. One research study found that emergency room visits for migraines went up 7.5% for each 9-degree increase in air temperature.2
  • Environmental changes. A hypersensitivity to light, and flickering light in particular, is common in people who have migraines.3 Sources of flickering light can include computers, movies, television, and fluorescent lighting. Loud noises and strong smells also lead to migraines in some cases.
  • Hormonal changes in girls and women. Migraines that are more common before and during menstrual periods are typically called hormonal or menstrual migraines.

When migraines are triggered by hormonal changes associated with menstruation, a health care provider may prescribe preventive medications to be started in the days leading up to the menstrual period.

Alternatively, women taking birth control pills may consider taking a continuous level of medication throughout the cycle, rather than skipping several days each month. The continuous type of medication may be less likely to trigger a migraine. This option may affect what birth control is prescribed and should be done only in consultation with a health care provider.

Exposure to two or more triggers further increases the risk of a migraine occurring.

Headache Diary Helps Track Potential Triggers

Substances that trigger a migraine in one person may not bother another. Keeping a headache diary can reveal patterns that were missed before. These patterns can show which foods should be avoided and what medications help the most.

The following items are helpful to track each day:

  • Foods
  • Drinks, including alcohol, caffeine, or artificial sweeteners
  • Exercise
  • Events preceding migraine
  • Severity of migraine
  • Duration of migraine
  • Timing and type of medication taken
  • Effectiveness of medication
  • Days of menstrual cycle, for women

Identifying individual triggers, and how to avoid them, can significantly improve quality of life by keeping migraines from occurring as frequently. About 40% of people with migraines can cut the number of migraines in half through treatment and lifestyle changes.4


  • 1.Mukamal KJ, Wellenius GA, Suh HH, Mittleman MA. Weather and air pollution as triggers of severe headaches. Neurology. 2009;72(10):922-7.
  • 2.Karanovic O, Thabet M, Wilson HR, Wilkinson F. Detection and discrimination of flicker contrast in migraine. Cephalalgia. 2011;31(6):723-36.
  • 3.American Migraine Foundation. Identifying & Treating Migraine.
  • 4.Wells RE, Burch R, Paulsen RH, Wayne PM, Houle TT, Loder E. Meditation for migraines: a pilot randomized controlled trial. Headache. 2014;54(9):1484-95.