What Are Common Causes of Chronic Headaches?

Chronic headache refers to frequent onset of headaches for more than 15 days per month, and headaches last more than 4 hours per day. There are two types: primary and secondary. Primary chronic headache refers to headaches that exceed 15 days per month without organic or systemic diseases, including migraine, tension headache and cluster headache. Traumatic pain caused by brain trauma, brain tumors, encephalitis, stroke, and lesions in surrounding organs.