Two types of severe headaches are being linked to the body's internal clock. Cluster headaches cause an intense burst of pain around the eye that can last for about 15 minutes and reoccur for up to three hours. A new study published Wednesday says cluster headaches are more common in males than females, unlike migraines which are more common in females, and that cluster headaches usually happen at night while migraines usually come during the day. The scientists at the Will Erwin Headache Research Center in Houston say the body's circadian rhythm appears to be involved in both headache disorders.
Photo: Getty Images