Pain is an unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse. Some pains are easy to understand because there is obvious injury such as bleeding or a bruise. Some are less obvious. Short-term pain like an ankle sprain is called acute pain; long-term, continuous pain is called persistent or chronic pain, while pain that comes and goes is called recurrent or intermittent.
Many acute pains are a useful alarm signal that something is wrong. Most minor ones may be easy to rub better or treat yourself; others may be a sign of something more serious such as a broken leg. The pain is useful because it ensures that you rest the leg until the break has had a chance to heal.
Persistent pain is different from acute pain. The warning system goes into overdrive and sends out repeated pain signals which are not needed or are out of proportion so they serve no useful purpose.
All pain signals travel from the painful part of the body along nerve fibres through the spinal cord to the brain. The spinal cord does not just pass on nerve messages but processes them. In persistent pain, sorting mechanisms for nerve messages go wrong and the brain is confused. This may lead to changes in the pain processing system. Cells that were previously “asleep”, may become “awake” and start sending pain signals to the brain all the time. This is called “wind- up” and is one of the reasons why chronic pain does not go away easily, even if the cause of the pain is discovered and treated. This can lead to a long term, distressing problem.
Pain signals are also processed in the brain where they connect with emotional centres such as anxiety, sleep and appetite centres. The brain sends signals back to the spinal cord, which can, in turn, reduce or increase the pain further. Pain is never “just in the mind” or just in the body; it is a complex interweaving of pain signals and their interpretation by the brain.
The situation in which we receive painful stimuli also make a difference to the way we feel pain. In the heat of the moment even a severe and subsequently painful injury may go unnoticed, for instance if we are involved in an exciting sports match. We might not realise how serious a cut is until we look at it. On the other hand, if we are stressed or depressed we may not be able to stand even a small amount of pain, it becomes overwhelming and makes us feel even more depressed.
Only the person in pain can really say how painful something is as pain is personal and subjective. No two people experience it in the exactly the same way. That makes it very difficult to define. Unfortunately, there is more to persistent pain than just hurting. This is unpleasant enough by itself but when it continues for a long time, it can affect all aspects of your life. It may affect your ability to work, your personal relationships with family and friends, your activity levels and your sleep. About 50% of sufferers become depressed and anxious.