Editor's note: Video sound bites of Dr. Lollie Hagen speaking to this topic are available for media. Download 720p version here. Download the SD version here. Download accompanying b-roll here.

Nearly everyone at some point has experienced a headache. The World Health Organization estimates that 47 percent of adults have experienced a headache in the past year.

However, not all headaches are the same. Some may cause a person minor discomfort, but some can be extremely painful and debilitating. Some headaches may also indicate the presence of other serious health problems.

What is a headache?

A headache is pain or discomfort in the head, scalp or neck, according to the National Institutes of Health.

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Headache disorders fall into two broad categories. A primary headache is a headache due to the headache condition itself and not brought on by another cause while a secondary headache is a headache caused by another condition.

Primary headaches include tension-type headaches, migraines and cluster headaches.

Tension-type headaches are often described as experiencing pain that feels like a tight band is squeezing your head or a weight is sitting on your head. It is the most common type of headache and accounts for about 90 percent of all headaches.

Causes of tension-type headaches are emotional stress, anxiety, depression, poor posture and lack of sleep.

Tension-type headaches can become disabling when they are chronic. Overusing pain killers to treat tension-type headaches can cause daily chronic headaches.

Dr. Christine “Lollie” Hagen , a neurologist at Novant Health Winston Neurology – Kernersville Headache Clinic, said the most common headache type she sees at her practice is migraine. “Thirty-six million Americans suffer from migraine headaches,” she said. “More people have migraines than have diabetes or asthma.”

Migraines are common and debilitating headaches, according to the International Headache Society. The society said that migraines can present with or without an aura. Migraines without aura are recurrent headaches that last anywhere between four to 72 hours.

Patients describe the moderate to severe pain as throbbing in one area of the head. During an episode, patients are very sensitive to light and sound and they may also experience nausea and vomiting. Routine physical activity such as walking can aggravate the pain. Women are more likely than men to suffer from migraines.

“Approximately 18 percent of women suffer from migraine headache compared to roughly 6 percent of men. Also, about 80 percent of people with migraine have a family link associated with their migraine headache,” Hagen said.

“Migraines can be very debilitating,” the doctor said. “Migraines contribute to more missed work than any other disease, so not only is it painful for the patient but it’s costly to our society as a whole.”

In cases of migraines with aura, patients experience warning symptoms hours or even a day before the attack including fatigue, sensitivity to light or sound, nausea or blurred vision. The migraine will develop gradually over five to 20 minutes and usually last less than hour.

“Migraine is a spectrum disease so symptoms can be mild, moderate or severe,” Hagen said. “In about one out of 50 patients, migraines will be chronic, which can produce headaches 15 or more days per month.”

Cluster headaches cause intense, repeated bouts of pain on one side of the head. During a bout with cluster headaches, the pain can occur at the same time each day often at night and become intense for half an hour to an hour. Episodes occur regularly for a week to a year and are separated by periods without pain. Patients may also experience watery eyes and a stuffy nose during an attack.

Cluster headaches present very differently from migraines, according to Hagen. “They’re a shorter duration headache lasting an hour to two hours, but the intensity goes from zero to 10 right away,” she said. “People experiencing a cluster headache will want to move, they’ll pace the floor while migraine patients want to be still.”

Cluster headaches are more common in men and tend to run in families, the doctor added.

Hagen said cluster headaches are also rarer. In her clinic, 95 percent of patients suffer from migraines and 5 percent have cluster headaches.

“Cluster headaches can be very hard to diagnose,” Hagen said. “Patients will wake up in the middle of the night in intense pain. They’ll go to the emergency room. The next night they might experience the same pain so it might take a while for a provider to understand it’s a cluster headache.”

Secondary headaches are caused by other conditions such as high blood pressure or infections such as sinusitis or meningitis. A mild head injury can cause a headache and so can tumors in the head. Blood vessel problems, such as a hemorrhage following the rupture of an aneurysm, can also cause a severe headache.

What are the causes of a headache?

A number of factors can trigger a tension-type headache. including stress, depression, anxiety, a head injury, or holding your head and neck in an abnormal position.

The pain in a tension headache usually affects both sides of the head, starting at the back and spreading forward. It can be accompanied by soreness in the shoulders, neck or jaw.

Researchers are not certain what causes migraines. Hagen said that the scientific community sees it as an attack on the brain because of genetic predisposition and an inflammatory component associated with the disease.

“On average, most people have about six triggers for their migraines,” Hagen said while pointing out that many disparate factors may play a role. “Patients may have a genetically susceptible brain. Weather changes or hormonal changes and foods that you eat or caffeine or smoking cigarettes all can trigger a migraine. So the healthier you are, the less intense the headache.”

Foods that can trigger migraines may include chocolate or certain types of cheese or seasonings such as monosodium glutamate or nitrites in processed meats. Other triggers may include caffeine withdrawal, alcohol and lack of sleep.

Headaches that keep reoccurring are known as rebound headaches and can be due to overuse of pain medications. People who regularly take pain medications more than three times a week may be susceptible to rebound headaches.