While migraine headache is far more common in women, cluster headache is more common in men. The term "cluster headache" is used to describe the clustering of short, painful, one-sided headache attacks. These attacks can occur many times during the day from weeks to months at a time, and then stop for a few weeks or months.

Approximately 80 percent of Americans will have at least one bout with back pain during their lifetimes, according to the American Association of Orthopedic Surgeons. In fact, Americans see their doctors for low back pain more than any other reason except the common cold and flu.

When pain lasts for a long time, it is considered to be chronic pain. Many physicians consider pain to be chronic when it has lasted for six months or longer.

Postherpetic neuralgia is a painful condition that can follow an episode of shingles. The term comes from the words “post,” meaning after, “herpetic,” referring to herpes zoster (shingles), and “neuralgia,” meaning nerve pain. Shingles is a recurrence of the varicella-zoster virus, the same virus that causes chickenpox.

Chronic pain has been under-treated in part because the traditional practice of medicine was to focus on an underlying disease and not its symptoms. However, as pain came to be considered by many to be, itself, the disorder, a newer branch of medicine has evolved that deals specifically with pain management.

Back pain is one of the most common medical problems, affecting 8 out of 10 people at some point during their lives. Back pain can range from a dull, constant ache to a sudden, sharp pain.