Ah I am so stressed! My head hurts! Headaches are very common in our society and in fact, more than 90% of people suffer from headache at some point in their lives. Headache could be either caused by internal or external stimuli. Some people experience recurring headaches due to some physical illness while others only have headache when they are stressed or undergoing other emotional distress. As headaches are closely associated with our daily lives, it is beneficial to learn about the different types of headaches, their causes and features.