Potential causes of morning headaches may include withdrawal effects from caffeine or pain medications, or a history of migraines or cluster headaches and depression, according to the National Headache Foundation. Serious diseases such as sleep apnea, sleep disorders, severe high blood pressure and brain tumors may also cause morning headaches.
Individuals with high blood pressure may be susceptible to headaches between 4 and 8 a.m. due to the release of adrenalin in the body, explains the National Headache Foundation. The body typically produces less endorphins and enkephalins, which are natural painkillers, during these hours, and a larger quantity of adrenalin is released. Adrenalin can affect a person's blood pressure and the dilation or contraction of blood vessels. If severe high blood pressure exists within a person's system, a migraine attack or chronic tension headaches could occur in the early morning hours.
Sleep disorders also play a role in morning headaches, also known as awakening headaches, reports the American Headache Society. For example, oversleeping or sleep loss can trigger headaches. Snoring, insomnia, jaw clenching, sleepwalking and restless leg syndrome are also sleep disorders that trigger headaches in the morning. People who sleep seven to eight hours each night are less likely to develop morning headaches.