A condition involving pain or discomfort in the head, scalp, or neck, usually associated with muscle tightness in these areas.  Tension headaches are one of the most common forms of headache.  They can occur at any age, but are most common in adults and adolescents.  If a headache occurs two or more times weekly for several months or longer, the condition is considered chronic.  Tension headaches result from the contraction of neck and scalp muscles.  One cause of this muscle contraction is a response to stress, depression or anxiety.  Any activity that causes the head to be held in one position for a long time without moving can cause a headache.  Such activities include typing or use of computers, fine work with the hands, and use of a microscope.  Sleeping in a cold room or sleeping with the neck in an abnormal position can also trigger this type of headache.  Other causes include spinal misalignment, eye strain, fatigue, alcohol use, excessive smoking, excessive caffeine use, sinus infection, nasal congestion, overexertion, colds, and influenza.  Tension headaches are not associated with structural lesions in the brain.