Christine Weaver, age 9, of San Diego, Calif., for her question:

WHAT CAUSES A HEADACHE?

More than 100 underlying problems could be responsible for the headache you receive. What actually happens is that there is an increased blood flow to the head with pressure within that irritates the pain receptors of the nervous system.

A headache is actually a cry that says "Slow down." It is more than just a symptom.

Simple nervous tension is often the trigger that produces a headache. Sometimes it can be almost unbearable when other times it can be quite mild.

Migraine headaches are those usually caused by emotional tension that cause the arteries of the head, including those that reach the brain, to go into a spasm. As they draw together, they restrict the flow of blood and produce headache symptoms.

Don't worry too much about simple headaches. We all have them. But be sure to see your doctor if they persist.