The cause of headaches is a not definitely known in every patient for every type of headache. A number of mechanisms have been proposed. Particularly in Tension-Type headaches, it is felt that excessive muscle contraction around head and neck muscles are a significant factor in the developing of the headache. Another proposed cause of headache relates to the levels of serotonin in the brain. This neurotransmitter is important in a variety of aspects including mood and pain and even has effect on blood vessels. The serotonin mechanism as a cause of headaches is felt to possibly relate to muscle contraction headaches as well as migraines. It has been recognized that blood vessels in migraine headaches will constrict and dilate during the course of a migraine headache and how this exactly relates to the pain or whether it is a reflection of other underlying processes is not definitely known.