For example, scientists long thought the constriction and expansion of blood vessels could trigger migraine pain. In fact, it’s more likely that any blood vessel dilation is a symptom—not a cause.¹

There’s still much to learn about what causes migraine headaches. However, the researchers looking at chemical and hormonal imbalances believe they are closer to an answer.

A Body in Balance

Your brain is a huge network of nerve cells (neurons) that together make up the nervous system. While neurons are connected to many other cells, they are not directly linked to one another. Instead, neurotransmitters send chemical signals, which body and brain receptors pick up. This is how your body processes and regulates emotions, pleasure, memory and your perception of pain.

Your brain has two types of neurotransmitters:

• Excitatory neurotransmitters produce chemicals (e.g., dopamine) in response to external input, which can range from sound and light to odor and even the weather.
• Inhibitory neurotransmitters produce chemicals (e.g., serotonin) to help calm your nervous system.

It’s the job of the neurotransmitters to maintain a chemical balance in your body and brain. When loud sounds, bright lights, strong odors, weather changes and other input stimulate your excitatory neurotransmitters, the inhibitory neurotransmitters increase serotonin, which narrows blood vessels.

The trigeminal nerve is one of 12 sets of cranial nerves that regulate the senses as well as the spontaneous activity of your organs and blood vessels. The trigeminal nerve does about 70% of all the cranial nerves’ work—especially in the face and head. Research is finding that brain cells and hormones can trigger the trigeminal nerve to cause swelling in blood vessels and send pain signals to the brain.³

When chemical imbalances and hormonal fluctuations occur, some people experience migraine headaches. The role of estrogen may explain why about three times as many women as men get migraine headaches. It also may be why many women first experience migraines with the onset of menstruation and why their frequency declines with menopause.

The Role of Triggers

When people talk about what causes their migraines, they often discuss the triggers. These are some combination of activities, behaviors, foods and environmental stimuli that seem to trigger a migraine attack.

In fact, these triggers may be setting off a chemical or hormonal chain reaction in your body. It’s easy to imagine, for example that too much stress or too many nights of interrupted, deep sleep and the associated restorative REM cycles might inhibit your neurotransmitters from doing their job.

It’s important to note that not every migraine sufferer has the same triggers. This is why your doctor will probably ask you to record your activities, environmental influences and more that have occurred before a migraine attack.

Here’s a short list of triggers:

• Food and Food Additives (e.g., nitrates, artificial sweeteners, MSG)
• Caffeine and Alcohol (especially red wine)
• Excessive Tiredness
• Irregular Eating and Sleeping Habits
• Environmental Stimuli (e.g., bright lights, loud noises, strong odors)
• Dehydration
• Menstrual Cycles
• Stress

The Role of Genetics

Researchers estimate that about 90% of people with migraines have one or more family members who also suffer from migraines. And a 2010 research study based on genetic data from more than 50,000 Europeans found an inherited neurological condition that is common in the DNA of migraine patients.4 This genetic variant disrupts the balance of glutamate neurotransmitters in the brain. Scientists still have much more work to do to understand how genetics and triggers play into why people get migraines. Their research, however, is already helping physicians advance the use of therapies and treatments to help reduce and even prevent the severity, duration and frequency of migraines.