Headaches are among the most common disorders of the nervous system. It has been estimated that 47% of the adult population had a headache at least once within last year in general according to the World Health Organisation 
Headaches are "underestimated, under-recognized and under-treated throughout the world".
Types of Headaches:
Migraine: A primary headache disorder which is recurrent, often life-long, and characterized by attacks.
Tension Headaches: The most common primary headache disorder.
Cluster Headaches: A primary headache disorder but relatively uncommon.
Medication-overuse Headaches: Caused by chronic and excessive use of medication to treat headache and is the most common secondary headaches.
Headaches usually happen for a reason and for many people chiropractic treatment can be a very effective way of treating headaches.
Headaches can be caused by misalignments in the neck (the cervical spine) or the shoulders so to determine if this is the case, a thorough Consultation is carried out before any treatment is made.
 The WHO. http://www.who.int/mediacentre/factsheets/fs277/en/