Tension-type headache is classified as headache type 2.0 in the IHS Classification and is further subclassified into 2.1: episodic tension-type headache, 2.2: chronic tension-type headache, and 2.3: tension-type headache not fulfilling the above criteria. Muscle contraction or tension headache has been characterized as head pain without migrainous features. Typically, the headache is described as bilateral, commonly in an occipital or posterior neck location, variable in intensity, dull, with pressure and tightness in muscles and in association with emotional conflict.{14,198} They tend to occur on a daily basis but may be intermittent or periodic. On careful analysis there are many overlapping features common to migraine. Features at one time believed to be specific for tension headache, such as neck muscle contraction and precipitation by stress and anxiety, are know known to occur just as often in migraine.199 Indeed many patients with daily constant headache, without throbbing and having a "band-like" tightness may respond to antimigrainous therapy. At one point an Ad Hoc Committee on Classification of Headache recommended separate categories for "Headaches of Delusional, Conversion, or Hyperchondriacal States" and for "Muscle-Contraction Headache" but others prefer to combine these into a category of "psychogenic headaches" under which there are the subtypes: depression (overt or masked), delusional (in a psychotic), somatoform disorder, chronic post-traumatic, chronic atypical facial pain, and muscle contraction pain (when due to psychogenic factor and not unusual postures or strains).{198} In the present classification, there is not a separate category for headaches of psychogenic origin and they would be classified as 13.0: headache not classifiable. Clearly there are patients with major psychological problems who have psychogenic headaches as a feature of their disorder, but in a majority without features which permit a diagnosis of probable or definite migraine, the distinction is often difficult. Muscle contraction or tension headaches do overlap significantly with migraine, as indicated above, and may respond to similar therapy. Antidepressant therapy in the form of tricyclics may be helpful in both muscle contraction and migraine headaches but I use such agents primarily to treat the accompanying depression of chronic headache.