군발 두통, also known as cluster headache, is a type of severe headache that occurs in cyclical patterns or clusters. These headaches are characterized by intense pain, usually on one side of the head, often around the eye. They can last from 15 minutes to three hours and may occur multiple times a day during a cluster period. The exact cause of 군발 두통 is not fully understood, but it is believed to involve the hypothalamus, a part of the brain that regulates biological rhythms. Triggers can include alcohol, smoking, and changes in sleep patterns. Treatment options include medications and lifestyle changes to help manage symptoms.