What Is a Headache?

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Chapter 1
What Is a Headache?

Just as the name implies, a headache is a pain in all or part of the head that may also be felt in the face and neck. A headache can be a symptom of disease, in which case it is known as a secondary headache. Infectious diseases, such as the common cold, influenza, and pneumonia, often produce secondary headaches, as does an allergic reaction or a sinus infection. Secondary headaches are also a symptom of the eye disease glaucoma, high blood pressure, stroke, head injury, a brain tumor, and a teeth-grinding condition known as temporomandibular joint (TMJ) syndrome.

Ninety percent of all headaches, however, are unrelated to any other medical condition. These headaches are called primary headaches. Primary headaches may be episodic, which means they occur occasionally, or they may be chronic. Chronic headaches strike at least four times a month and usually affect a person for most or all of his or her life. Debbie, one woman who has had chronic headaches for more than twenty years, describes her experience: "I started getting headaches in my early twenties. A lot of times, I wake up in the middle of the night with a bad headache. I get them at work too. I try to ignore them and go on with whatever I have to do. But since I get headaches about three or four times a week, it's hard. That's more than three thousand headaches in the last twenty years."4

Headache Causes

Scientists do not know exactly what causes headaches, but there are a number of theories on the subject. The most widely accepted theory is that headaches are caused by biochemical and blood-flow changes in the brain. According to this theory, headaches occur when an individual's nervous system reacts abnormally to otherwise harmless substances that he or she may eat, see, smell, hear, or feel. These substances are known as headache triggers.

When exposed to these triggers, the nervous system responds by producing a spasm in the arteries at the base of the brain. This causes the affected arteries to narrow or constrict, making it difficult for oxygen-rich blood to flow through the arteries and reach the brain. Therefore, the brain's supply of oxygen and blood is reduced. When the arteries narrow, blood cells called platelets can no longer move easily through the bloodstream. As a result, the platelets jam together. When they do, they become sticky and their walls become damaged, causing chemicals stored within them to leak out into the bloodstream.

One of these chemicals is serotonin. Serotonin is a neurotransmitter or chemical messenger. Like all neurotransmitters, serotonin is involved in carrying messages to the brain. These messages involve mood, sleep, pain production, and the widening and narrowing of blood vessels.

High levels of serotonin in the bloodstream signal the brain to act in a prescribed manner. Conversely, low levels signal the brain to act in an opposing manner. For example, high levels of serotonin signal the brain to constrict blood vessels and limit the body's response to pain. Low levels of serotonin, on the other hand, cause the blood vessels to widen and make the body more sensitive to pain. Therefore, when platelets leak excess serotonin into the bloodstream, the blood vessels are forced to narrow further. This results in an even greater decrease in the amount of oxygen and blood that reaches the brain.

Faced with a lack of blood and oxygen, the nervous system once again overreacts and suppresses the production of serotonin. Lack of serotonin causes blood vessels to widen, and makes the body more sensitive to pain. At the same time, the immune system responds by sending chemicals to the brain that cause inflammation and swelling. These chemicals cause other arteries within the brain to swell. The combination of narrowing and widening blood vessels, the presence of inflammation, and fluctuating serotonin levels cause a squeezing or throbbing pain in the head—a headache.

Different Types of Headaches

There are over 150 different types of headaches. The most common are tension, migraine, and cluster headaches, all of which are primary headaches. Of these, tension headaches affect the most people. In fact, according to headache expert and doctor of internal medicine Joel Paulino, tension headaches are the cause of 90 percent of all chronic, primary headache pain in the United States. In addition, an estimated 95 percent of people in the United States experience episodic tension headaches at one time or another.

Tension Headaches

Tension headaches are the least severe form. However, some people get chronic tension headaches on a daily basis, and this pattern of headaches can persist for years. Characterized by mild to moderate pain, tension headaches produce a persistent ache that makes people feel like their heads are being squeezed tightly. These headaches usually affect both sides of the head, as well as the part of the head where the head and neck muscles meet. Paulino describes how tension headaches made Juan, one of his patients, feel. The headaches, he explains, "led to a buildup of pain and tightness in his forehead and the back of his head and neck. Sometimes the pain felt like a tight band around his head." Juan told Paulino: "It feels like my head is held in a vise."5

Migraine Headaches

Migraine headaches are the second most common form of primary headaches, affecting 23 million Americans. Migraine headaches are usually more painful and more debilitating than tension headaches.

Unlike tension headache pain, migraine headaches usually affect only one side of the head, but may occur on the opposite side during another attack. Migraine pain can range from moderate to unbearable and is most often described as a throbbing or hammering pain. According to Lucy a migraine sufferer, "A migraine is like a freight train, a rugby game, and a mining operation, all going on and through your head at once."6

In addition to causing pain in the head, migraine headaches usually cause nausea and vomiting. This frequently makes it difficult for people with migraines to function. Dina describes what a migraine is like: "When I get a migraine, I can't function. I have to lay down with no lights and no noise. Before it is over, I start throwing up. Throwing up makes it worse, makes my head hurt more. It's horrible."7

Cluster Headaches

The third type of primary headaches is cluster headaches. Less common than tension or migraine headaches, cluster headaches affect about 2 million Americans. Said by both patients and doctors to be among the most painful of all headaches, cluster headaches typically appear in cycles or clusters. They usually strike five or six times a day for several consecutive days, weeks, or even months, then cease, only to return in the future. Approximately 10 to 20 percent of cluster headache patients have a form of cluster headaches that lasts more than a year and disappears for less than two weeks before returning. According to neurologist Peter Goadsby, director of the Headache Group of London's Institute of Neurology, "Cluster headache is probably the worst pain that humans experience. I know that's quite a strong remark to make, but if you ask a cluster headache patient if they've had a worse experience, they'll universally say they haven't."8

Typically, cluster headaches begin and end suddenly. The pain, which is often described as sharp and stabbing, usually comes from behind one eye and affects only one side of the head, but may affect the opposite side during another attack. "They come on very rapidly," John, a cluster sufferer, explains:

You suddenly realize that you have a pain behind your eye.… As soon as you get the first twinge you know that within five minutes you may lose control of yourself and be reduced to whimpering.… Violent pain doesn't generally last; if you bang your head against something it hurts for a moment then it subsides. It just doesn't subside with a cluster headache, it goes on… and then all of a sudden it stops.9

Headache Triggers

No matter what type of headache a person gets, exposure to specific headache triggers stimulates an individual's nervous system to react abnormally. Although headache triggers do not cause headaches, they do induce the chain of events that produce a headache in certain people. Scientists say that some people are more sensitive to headache triggers than others and thus are more susceptible to headaches. But they do not know why this is so. Scientists do know that most headache triggers are dietary, environmental, hormonal, or connected to a person's lifestyle.

Dietary Triggers

Dietary triggers are common headache triggers. In fact, it is estimated that 30 percent of all headache triggers are dietary. Almost any food or beverage can be a headache trigger. However, certain dietary triggers are more common than others. Among these are nitrates, which are chemicals found in processed meats such as hot dogs, sausage, salami, and bologna. At high doses, nitrates are known to dilate the blood vessels. In fact, the medicine nitroglycerin, which is used to treat heart patients with constricted blood vessels, is a nitrate. Although the amount of nitrates found in processed meat has no effect on the blood vessels of most people, scientists think that even low doses of nitrates may affect the blood vessels of susceptible people.

Other common dietary triggers include chemicals known as amines; the food additive MSG, or monosodium glutamate; and the food preservative sulfite. Amines are commonly found in chocolate, cheese, yogurt, red wine, raisins, tuna, salmon, tomatoes, citrus fruit, and legumes such as beans, nuts, peas, and soy products. MSG is often used in oriental cooking, while sulfites are found in dried fruit and alcoholic beverages. Scientists do not know why these substances trigger headaches. They theorize that certain people are unable to break down these substances when they ingest them, which affects their blood vessels.

Environmental Triggers

Environmental triggers also affect many headache sufferers. These include air pollutants, weather changes, certain odors, bright lights, and loud noises. Air pollutants like smoke and gasoline fumes, for example, raise carbon monoxide levels in the air while lowering oxygen levels. Although breathing in polluted air is not healthy for anyone, for people susceptible to headaches, even minor changes in the amount of oxygen inhaled, and thus the amount that enters the bloodstream, can trigger a headache. Debbie, a sufferer whose headaches are triggered by air pollution, describes her experience: "Pollutants in the air always give me a headache. The other day I went to the airport to pick up my daughter. That night I woke up at 2:00 A. M. with a terrible headache from the pollutants in the air in El Paso [the city where the airport is located]. My head hurt all day."10

Other environmental triggers, like weather changes, include not only changes in temperature, but also changes in air pressure and humidity. According to doctor of internal medicine and headache expert Dennis Fox, 43 percent of headache patients report that weather changes trigger their headaches. High winds in particular appear to be a widespread trigger. Scientists theorize that this may be due to electrical changes in the air, which somehow may affect serotonin production in susceptible people.

Bright lights and glare from sunlight, fluorescent lights, or a television or computer screen also are common environmental triggers. Bright lights stimulate the brain, as well as cause people to tense muscles around their eyes and forehead in order to squint or block out light. Both these factors may prompt the arteries in the head to spasm and thus induce a headache. Loud noises and powerful odors, too, stimulate the brain and cause people to tense muscles in the face and head. Strong perfumes seem to trigger headaches in many people. Headache expert and neurologist Christina Peterson explains: "Highly complex perfumes with many aromatic components tend to pose the biggest problems, along with heavy, spicy perfumes. I avoid wearing most perfumes to the office, as I would hate to trigger someone's migraine."11

Hormonal Triggers

Another common headache trigger is hormonal changes in a person's body. Hormonal changes are often associated with puberty, a woman's menstrual cycle, and pregnancy. Experts say that fluctuations in the level of hormones, chemicals produced by the body, may also affect serotonin production. Therefore, it is not surprising that many young women start getting headaches during puberty, or that many pregnant women suffer from headaches, since these are both times when a female's hormones rise and fall frequently. Indeed, scientists have proven that in the days before a woman's menstrual period begins, levels of the female hormone estrogen fall. Interestingly, low levels of estrogen have been linked to a decrease in serotonin production. This may be the reason many women report getting headaches in the days before the start of their menstrual period. Cindy, who suffers from premenstrual headaches, explains: "I always know when a headache is coming on. It always starts about thirty-six hours before my period arrives. I start taking Tylenol before it [the headache] starts, because I know it will."12

Lifestyle Triggers

Certain lifestyle factors also are known to trigger headaches. These include lack of food, intense exercise, stress, and irregular sleep patterns. Intense exercise and skipping meals can cause blood sugar levels to drop. Low blood sugar causes the body to release the hormones adrenaline and cortisol that, like the hormone estrogen, are linked to a decrease in serotonin production. In addition, the presence of these hormones increases a person's sensitivity to pain. Debbie, whose headaches are not only triggered by air pollution but also by lack of food, explains: "If I don't eat right, or if I go too long without eating, I get a real bad headache. When I start getting a headache, one of the first things I ask myself is when I last ate."13

Stress, too, causes the body to release adrenaline and cortisol into the bloodstream. Therefore, it is not surprising that stress is a widespread headache trigger. In fact, stress is the most common of all headache triggers, responsible for approximately 63 percent of all headaches.

Irregular sleep patterns also trigger headaches in some people. A study at Case Western Reserve University in Cleveland, Ohio, of children with migraines, for example, reported in the April 2003 issue of Headache: The Journal of Head and Face Pain, that 42 percent of the subjects did not get enough sleep. Scientists do not know why irregular sleep patterns trigger headaches but theorize that they affect the working of the brain and cause fluctuations in serotonin levels.

Multiple Triggers

Most headache patients are sensitive to multiple triggers. When a person is exposed to a number of triggers simultaneously, his or her chance of developing a headache becomes greater, as does the severity of the headache. The reason for this is that the more triggers, the more powerful the effect. Complicating matters, trigger combinations can vary at different times. For instance, a person may be sensitive to wine, loud noise, stress, and air pollution. If the person is exposed to loud noise alone, a headache may not develop. But if the person drinks wine in a noisy, smoky bar, the chance of a headache developing increases significantly. At another time, the same person might react to a different combination, and for those people who are sensitive to a wide number of triggers, the combinations can be extensive.

People at Risk

No matter what triggers a headache, it is clear that almost everyone gets one occasionally. Headaches strike people of all ages, races, and genders. However, certain people are at risk of developing chronic headaches. One such group of people is women. Migraine headaches, in particular, seem to strike women more frequently than they do men. Of the 23 million migraine patients in the United States, 18 million are women. Moreover, most of these women are between twenty and fifty years old. This is typically the time in a woman's life when she experiences fluctuating hormone levels tied to her menstrual cycle, which experts theorize play a great role in putting women at risk. Conversely, men are at a six-times greater risk than women of developing cluster headaches. Scientists cannot explain why.


Both males and females who have family members with chronic headaches are also at risk. All types of headaches, and migraines in particular, appear to run in families. According to Paulino, between 70 and 80 percent of all migraine patients have family members with migraines. Scientists have not yet found a specific gene that causes or predisposes people to headaches. However, based on statistics of multiple family members with headaches, scientists theorize that some people inherit a sensitivity to headache triggers, which makes them more susceptible to headaches. Cindy describes how headaches affect her husband's family: "My husband's brother has migraines, so does his sister, her daughter, and now her son. Recently, our son said he had a migraine too."14

Physical Effects of Headaches

No matter who gets them, headaches have a physical impact. Headaches affect the brain and central nervous system. Since the central nervous system is the command center of the body, when there are problems here a ripple effect is produced throughout the body. For example, when a headache is occurring, nerve cells (neurons) in the brain often receive faulty messages and, in turn, release neurotransmitters that carry these faulty messages to the rest of the body. Therefore, the physical impact of headaches is felt not only in the head, face, and neck, but throughout the whole body.

For this reason, headaches can cause nausea; vomiting; dizziness; fatigue; sensitivity to light, sound, and smell; numbness; nasal congestion; facial swelling; tearing; and swelling and drooping of the eyelids. Although these problems generally subside when the headache ends, frequent vomiting can cause permanent damage. Since vomit is extremely acidic, frequent vomiting can damage the lining of the throat, mouth, and esophagus, and has been linked to cancer in these areas.

Emotional Effects of Headaches

Besides having a physical effect, headaches also have an emotional effect. Because headaches can be so painful and disruptive, many people with chronic headaches report feeling sad and resentful about the toll headaches take on their lives. They also report feeling chronic anxiety about when and where a headache will strike. Indeed, according to Fox, 60 percent of chronic headache patients suffer from chronic anxiety. Laura, a headache sufferer, explains: "One of the worst parts is the fear of when it [a headache] will rear its ugly head. You never know when you're going to lose twenty-four hours or forty-eight hours. Where am I going to be when it hits? Will I be driving my car? At my sister's wedding? It's the not knowing that's almost worse than the pain."15

Feelings of anxiety, resentfulness, and sadness cause many headache patients to become depressed. When people are depressed, they feel tired, have trouble sleeping and concentrating, and lack an interest in everyday life. Indeed, depression is more common among headache patients than among the general population. According to Fox, 30 percent of chronic headache patients suffer from depression. The statistics are even higher among migraine patients. According to a joint British and American study led by neurologist Dr. Richard Lipton of the Albert Einstein Institute in Bronx, New York, in 2000, 47 percent of migraine sufferers are affected by depression. In fact, researchers think that there is a direct link between headaches and depression. They do not know whether this link is strictly emotional or if decreased serotonin levels, which are involved in causing both headaches and depression, play a role.

Of course, not every headache patient suffers from depression. However, because severe or chronic headaches take a physical and emotional toll on people's lives, it is important that people suffering from them seek medical help.

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What Is a Headache?

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