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, which 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.
Brain Chemicals (Neurotransmitters)
Neurotransmitters are chemical messengers in the brain. Several types of neurotransmitters affect 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 type of headache medication can produce this effect. Headaches can also occur after withdrawing from caffeine, nicotine, or alcohol.
Review Date: 11/15/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.