I've already discussed many possible causes of fibromyalgia and chronic pain. But what if none of these possibilities explains your pain?

Or what if you do have one or more of these diagnoses, but so far treatment hasn't lessened your pain? All too often, such patients are told (or are led to believe) that their doctor thinks the pain is "all in their head."

The reality is that pain is a subjective experience. It is very difficult to describe pain, much less measure it objectively. Even when no obvious physical cause of pain can be found, the discomfort is very real. So in this sense, no, it is not all in your head.

However, pain must be processed by the brain in order for you to experience it and know it is there. Thus, some component of pain is always going to reside inside your head, even when it comes from something as obvious as a freshly stubbed toe.

Your mood also plays a big part in how severe you perceive your pain to be. Have you noticed that when you're feeling really good emotionally, your pain seems less severe? Or when you're doing something fun, you don't even notice that you've had a minor injury?

Chances are, you're not just feeling good because the pain has become less severe. Rather, your better mood is helping to reduce your pain. And just the opposite is also true — on bad days, everything hurts more.

A lot of this effect is due to endorphins, the natural brain chemicals released when you exercise and when your mood is good. Endorphins block pain by working on the same targets as potent narcotics like morphine and codeine.

Not knowing why you have pain is stressful for most people. If a thorough workup doesn't turn up any explanation, you may feel anxious about what's really wrong and what else might happen in the future. Unfortunately, the more you worry about the pain and what it means, the more severe your pain is likely to become.

Depression not only worsens existing pain, it can itself also be a primary cause of pain. Of course, it's depressing to have chronic pain and have to give up doing the things you enjoy. So, like the anxiety about what might be wrong with you, just having pain can make you depressed, and that depression can make the pain even worse.

Many people resist a diagnosis of depression, stress, or anxiety as being a cause of, or even a factor in, their pain. That's too bad, because these conditions are common problems for many people with chronic pain.

And whether or not other causes of pain are found or treated, any therapy that improves mood can help reduce pain. You can also see "Psyching Out Your Pain" for ideas about psychological approaches to treating pain.