Tension-type headache is defined as a primary headache disorder, i.e., headaches that exist independent of another disorder. These headache disorders are classified as chronic when they occur 15 days or more a month for six months in the absence of medication use. Chronic tension-type headache (cTTH) is characterized by pain (pressure, tightening or feeling like the head is being squeezed with a vice), frequently on both the left and right sides of the head. The pain can radiate from the lower back of the head, neck, eyes or other muscle groups. Individuals also report sensitivity to light and sound and may experience nausea.

Chronic TTH affects 2.2 percent and is more common in women than men. Age of symptom onset for cTTH most commonly begins in the teenage years.

Nearly 10,000 lost work days a year are attributed to headache, with 42 percent of those estimated to be due to tension-type headache.