Causes:

The causes of tension-type headache are still uncertain. Although tension-type headaches were once thought to be primarily due to muscle contractions, this theory has largely been discounted. Instead, researchers think that tension-type headaches occur due to an interaction of different factors that involve pain sensitivity and perception, as well as the role of brain chemicals (neurotransmitters). Genetic factors are likely be involved in chronic tension-type headache, whereas environmental factors (physical and psychological stress) may play a role in the physiologic processes involved with episodic tension-type headache.

Pain Sensitivity and Perception

Research indicates that patients with tension-type headache may have abnormalities in the central nervous system, (which includes the nerves in the brain and spine), that increase their sensitivity to pain.

Tension-type headaches may also be linked to myofascial trigger points in the neck and shoulder muscles. Myofascial pain involves the fascia (connective tissue) and muscles. Trigger points are knots in the muscle tissue that can cause tightness, weakness, and intense pain in various areas of the body. (For example, a trigger point in the shoulder may result in headache.) Because fibromyalgia is also characterized by myofascial pain, researchers are exploring whether there may be an association between this condition and tension-type headache. [See In-Depth Report #76: Fibromyalgia .]

Brain Chemicals (Neurotransmitters)

Neurotransmitters are chemical messengers in the brain. Several types of neurotransmitters have been identified as playing a role in increasing activity in pain pathways in the brain and affecting how the brain reacts to pain stimulation. In particular, serotonin (also called 5-HT) and nitric oxide are thought to be involved in these chemical changes. Release of these chemicals may activate nerve pathways in the brain, muscles, or elsewhere and increase pain.

Triggers for Tension-Type Headache

In addition to stress, many different factors can trigger or aggravate tension-type headaches:

Medication and Substance Overuse. About a third of persistent headaches -- whether chronic migraine or tension-type -- are medication-overuse headaches. These are the result of a rebound effect caused by the regular overuse of headache medications. Nearly any headache medication can produce this effect. Headaches can also occur after withdrawing from caffeine, nicotine, or alcohol.

Poor Posture and Work Conditions. Working or sleeping in an awkward position can contribute to posture problems (especially those that affect muscles in neck and shoulders) that trigger headaches. Eyestrain caused by overwork can also play a role.

Fatigue. Lack of sleep and tiredness from overwork are also headache triggers.

Foods and Beverages. Rapid consumption of ice cream or other very cold foods or beverages is the most common trigger of sudden headache pain, which may be prevented by warming the food or drink for a few seconds in the front of the mouth before swallowing. Not eating on time is also a trigger for headache.

Physical Activity. Intense physical exertion (including athletics or sexual activity) as well as lack of physical activity can trigger headaches. However, tension-type headache pain is not worsened by routine physical activity.

Dental Problems. Jaw clenching or teeth grinding, especially during sleep, are signs of temporomandibular joint dysfunction (TMJ, also known as TMD). TMJ pain can occur in the ear, cheek, temples, neck, or shoulders. This condition often coexists with chronic tension headache. Some patients with TMJ may see improvement in tension-type headaches from procedures or exercises therapies that specifically address the dental condition.

Physical Trauma. Whiplash or head or neck injury can lead to headaches.

Hormonal Changes. Hormonal changes, such as those that occur during the menstrual cycle or perimenopause, can affect headache occurrence.

Causes of Secondary Headaches

About 90% of people seeking help for headaches have a primary headache. The rest are secondary headaches, caused by an underlying disorder that produces headache as a symptom. More than 300 conditions can cause headaches. These can range from sinus conditions to brain tumor. While fear of brain tumor is common among people with headaches, headache is almost never the first or only sign of a tumor. Changes in personality and mental functioning, vomiting, seizures, and other symptoms are more likely to appear first.