The role of psychological factors related to headache, particularly tension-type headache (TTH), has long been a focus of investigation. The subject at issue is a complex one, with some aspects that are still being debated by experts. In episodic TTH, it is possible to hypothesise that headache is not only a "primary" headache that causes gratuitous pain to sufferers. In fact, it might represent an improper mode of communicating the sufferers' intimate discomfort, caused by an inadequate relationship between their personality profiles and events in their lives. As in migraine, in TTH, too, evidence has been found of comorbidity between headache and psychiatric disorders, including depression and anxiety disorder. Such evidence will have to be confirmed by further studies on the general population. As regards behaviour and personality traits, subjects with TTH had significantly higher scores than healthy controls on measures of automatic thoughts and alexithymia, and lower scores on assertiveness. Patients with chronic TTH had higher automatic thoughts scores than patients with episodic TTH. These findings suggest that people with TTH may have difficulty in expressing their emotions. Finally, psychological factors and emotional disturbances have been indicated as risk factors for TTH. Indeed, stress and mental tension are the most common factors that cause TTH.