Mike Kelly, age 10, of San Luis Obispo, Calif., for his question:

WHAT CAUSES INSOMNIA?

Insomnia is the inability to sleep naturally. Doctors say it is caused from any one of a number of causes. Indigestion or overexcitement may lead to insomnia. Pain or discomfort  from a physical illness can also interfere with sleep, and some people

 suffer from insomnia because coffee or other stimulants upset their nervous systems.

Doctors tell us that insomnia is a symptom or sign of an illness rather than an illness in itself.

Insomnia may be caused by psychological factors. It is often obviously related to conscious fears and worries, as for example when sleep is disturbed by frightening dreams. Everyone has occasional insomnia of this sort.