Chronic pain may develop for no apparent reason. Despite repeated exams and tests, your doctor may not be able to link your pain to a specific physical cause or condition. But this doesn't mean your pain isn't real.

So what's going on?

Often, the cause of chronic pain isn't well understood. Years of research have failed to uncover the precise physical causes of many painful ailments, including fibromyalgia, chronic fatigue syndrome and irritable bowel syndrome.

Sometimes a serious infection is followed by chronic pain. In other cases, altered electrical and chemical nerve signals cause pain to persist long after an injury has healed.

A heightened sensitivity to pain also may be a factor. People with chronic pain often have lower than normal levels of painkilling endorphins. In other cases, pain signals from injured or diseased tissue amplify or distort pain messages by activating pain circuits in the peripheral nervous system, spinal cord and brain.

Without an identifiable physical cause for your chronic pain, you may worry that the pain is all in your head.

"In a sense, pain is always in our heads," says David Martin, M.D., an anesthesiologist who specializes in pain medicine at Mayo Clinic, Rochester, Minn. "By definition, pain is a subjective and personal experience. Its existence cannot be proved. But what you feel is very real."

Chronic pain is a challenge — and you don't need to face it alone. Work with your doctor to manage your pain. Treatment options may include:

• Medication. Sometimes over-the-counter pain relievers or medicated creams or gels are effective. For more severe pain, your doctor may prescribe an opioid medication. Some people find relief with tricyclic antidepressants such as nortriptyline (Pamelor). Seizure drugs such as gabapentin (Neurontin) or carbamazepine (Tegretol) may relieve some types of chronic pain as well.
• Injection therapy. Instead of prescribing pills to control chronic pain, your doctor might inject medication directly into the affected area. Such injections are usually a combination of a numbing agent (local anesthetic), which provides immediate relief, and a corticosteroid, which reduces inflammation.
• Nerve stimulation. Various devices use electric impulses to help block or mask the feeling of pain. With transcutaneous electrical nerve stimulation (TENS), a portable, battery-powered unit delivers an electric impulse through electrodes placed on the affected area. Spinal cord and peripheral nerve stimulators are implanted beneath the skin with electrodes placed near the spinal cord. A hand-held unit allows you to control the level of stimulation.
• Medication pumps. An implantable medication pump supplies pain medication directly into the spinal fluid. To replenish the pump, drugs are injected through the skin into a small port at the center of the pump.
• Physical and occupational therapy. Stretching and strengthening exercises can improve your strength and flexibility. Sometimes learning new ways to handle daily activities can minimize the pain.
• Complementary therapies. Various complementary therapies may offer relief from chronic pain, including acupuncture, biofeedback, chiropractic care and hypnosis. Ask your doctor if such therapies may be helpful for you.
• Counseling. A counselor can help you manage your emotional response to chronic pain, as well as identify patterns of thought or behavior that may aggravate your pain.

Your lifestyle matters, too. Reduce stress. Do something relaxing every day. With your doctor's OK, exercise regularly. Build a solid support system. Focus on the good things in your life. Chronic pain may be unavoidable, but it doesn't need to control your life. Take action today.