Although medical science has not yet found the exact cause of headaches, some of the most common causes are related to everyday stress. Bad Headaches are broken down into three basic categories. A primary headache occurs to millions on a daily basis. Primary headaches are what the majority of headaches can be diagnosed as, and are almost never life threatening. Despite this frequency of occurrence and a lack of life threatening danger, a primary headache can be very painful. Cluster headaches are a much rarer and far more painful variety, that although not life threatening, can cause debilitating pain. Secondary headaches are sometimes a sign of a deeper neurological issue.