Understanding chronic pain

Acute pain has an important protective function: If you prick yourself on a thorn or touch a hot stove, for instance, it immediately hurts and you automatically pull your hand back. This prevents further injury. If you already have an injury, the pain reminds you that you need to take care not to touch or move it too much so that it can heal properly.

Chronic pain, on the other hand, usually doesn’t have a useful purpose. On the contrary: It can limit your ability to move freely, disturb your sleep, affect your performance at work and lead to exhaustion and psychological stress. It isn’t caused by acute damage, but instead develops due to a problem with the nervous system or a chronic inflammation.

Examples of chronic pain syndromes or medical conditions that cause chronic pain include the following:

• Osteoarthritis
• Diabetes
• Fibromyalgia
• Rheumatoid arthritis
• Back problems

Pain researchers differentiate between several types of pain:

• Nociceptive pain: This type of pain is caused by injuries, heat or problems affecting the tissue or organs. Examples include pain following bone fractures, colic due to kidney stones, or pain caused by a heart attack. They have an important protective function. In nociceptive pain, the pain messages are sent by special pain receptors known as nociceptors. Depending on what is causing it, the pain might be described as burning, stinging or pounding, for instance. Pain that comes from internal organs is often described as dull, deep or cramp-like, and it’s often hard to say exactly where it hurts.
• Pain caused by an inflammation: This kind of pain is caused when the immune system launches an inflammatory response – for instance, to an infection. Like pain caused by tissue damage, it has a protective function. In some diseases, though, the immune system attacks the body’s own cells and leads to long-lasting inflammations that can cause chronic pain. One example of this kind of disease is rheumatoid arthritis.
• Pain caused by nerve damage (neuropathic pain): This type of pain comes from irritated or damaged nerves and can be caused by various things, such as injuries, metabolic disorders and alcohol abuse. Examples of neuropathic pain include sciatic pain, nerve pain caused by shingles, and pain from diabetes-related nerve damage. Neuropathic pain is sometimes described as shooting or sudden pain, may be associated with tingling or numbness, and can make the nerves overly sensitive. If that happens, even weak signals are felt as pain. Neuropathic pain sometimes becomes chronic and takes on a life of its own. In other words, the pain stays although the damaged tissue has already healed.
• Pain caused by abnormal pain-processing: Sometimes pain is caused by a problem with the processing of pain in the brain. This pain is often non-specific – in other words, there is no known cause and it can be triggered by many things. Because there is no “reason” for the pain and it has no physiological purpose, it is also referred to as “dysfunctional pain.” Examples of this kind of pain syndrome include fibromyalgia, irritable bowel syndrome and a type of chronic bladder inflammation (interstitial cystitis).

Sometimes the causes of chronic pain are clear, for instance in osteoarthritis or rheumatoid arthritis. But it’s not uncommon for chronic pain to develop over a long time period, slowly get worse and gradually spread to other parts of the body. It is then often no longer possible to know what caused the pain originally – the pain has taken on a life of its own.

Sometimes people who have this kind of pain may end up having a lot of different examinations and tests to find out what’s causing it, but the tests might not lead to any useful answers. Instead, they often find supposed causes of the pain that actually have nothing to do with it. For instance, examinations in people with chronic low back pain may find normal age-related changes in the spine, sometimes leading to the false belief that these changes are causing the pain. Such misleading findings can cause unnecessary anxiety and treatments that don’t work – including unnecessary surgery.

It is currently thought that longer-lasting pain can leave “traces” in the nervous system, causing the nerve cells to become increasingly sensitive. This is sometimes referred to as “pain memory.”

Other processes may also play a role. For example, some animal studies have shown that nerve damage can cause nerve fibers to change. Nerves that send information about the senses then started sending pain signals as well. Long-term stress can affect pain processing in the brain too. Pain is then felt at lower thresholds or more intensely.

Acute pain can often be relieved with painkillers such as acetylsalicylic acid (the drug in medicines like Aspirin), ibuprofen and paracetamol (acetaminophen). But these drugs don’t work in many people who have chronic pain. Even strong painkillers such as opioids often don’t help them. Painkillers are associated with various risks and side effects, though. This is true for opioids, which can lead to dependency, as well as for over-the-counter painkillers such as diclofenac, ibuprofen and paracetamol (acetaminophen).

Pain researchers and specialists agree that chronic pain and acute pain need to be treated differently. It is important to develop strategies that help to cope better with pain in everyday life. Although this can’t get rid of the pain, it can relieve it in some people.

Things that are especially helpful in people with chronic pain include exercise, relaxation techniques and cognitive behavioral therapy with a focus on pain management. These are often combined in an approach known as multimodal pain management. Sometimes it’s also a good idea to use medication that influences the effects of chemical messengers (neurotransmitters) on the nerve cells.

If you’re in pain, it might seem logical to get lots of rest. This is what people were advised to do in the past, too. Nowadays, people who have chronic pain are advised to stay physically active and get regular exercise. When you exercise, your body releases substances that have a pain-relieving effect. Exercise also improves your blood circulation and stimulates your metabolism, making sure that your bones and cartilage get enough nutrients. It has other advantages too: Exercise improves your physical resilience, your ability to move and your sense of balance, which can help to prevent falls in old age. Last, but not least, it can improve your wellbeing.

People who aren’t used to exercising should start off slowly to avoid overdoing it. You can find out what type of exercise helps you by either trying out different things yourself or as part of exercise-based treatment. The aim of exercise-based treatment is to gradually increase your pain threshold again. There are special programs for a number of pain syndromes such as rheumatoid arthritis, fibromyalgia and chronic back pain, for example organized by support groups. In Germany, doctors can also prescribe something known as functional training (“Funktionstraining”) for up to 24 months.

It is often hard to understand how pain arises and how it is experienced. Pain research has led to some discoveries that might be surprising. For example:

• The fear of pain can be painful. Even if your body isn’t in any real danger and your tissue and organs are healthy, you may still feel pain – if your brain thinks you’re in danger. The purpose of this kind of pain is to help you avoid the thing that is thought to be dangerous. One aim of modern pain management is to reduce the fear of pain – for example, the fear of pain caused by exercising too much or doing the wrong kind of exercise.
• Pain that has no physical cause is still “real.” People who have pain for no known physical reason are sometimes accused of imagining it. That’s not true, though. Their pain just arises in a different way. A scientific experiment made this clearer: Healthy participants agreed to wear a cap that sends out electrical impulses that cause headaches – or so they were told. In actual fact, the cap didn’t send out any impulses or have any other effects. But the people in the experiment still felt pain – and the higher the “pain impulse” dial was turned up, the worse their pain became. The participants didn’t imagine the pain, though. They really felt it. This is because their brains thought they were being exposed to danger, so it produced pain signals.
• The severity of pain often isn’t directly related to the extent of physical damage. Very severe injuries like gunshot wounds don’t always cause immediate pain. Severe pain would make it harder for the wounded person to get out of danger in order to survive. Another example: Some people have severe damage to their spine caused by wear and tear but it doesn’t hurt – and some people have really bad back pain although no damage can be seen on x-ray images.
• Pain depends on outside factors. Pain severity can be influenced by how dangerous your brain considers something to be. This can be shown by the following experiment: A group of people volunteered to have a very cold metal pin (minus 20 degrees Celsius, which is about minus 4 degrees Fahrenheit) held against their hand for half a second. The metal pin either had a red light or a blue light on it. People who saw a red light felt more severe pain than people who saw a blue light – even though the temperature of the metal pin was the same, and it was held against their hand for the same amount of time. This is because we tend to associate the color red with danger and extreme heat, and see it as a more threatening color.
• Pain is influenced by how you feel. For instance, people feel less pain if their doctor takes more time for them and explains what is causing the pain. And pain may feel worse on a stressful day at work than at a weekend when out and about with good friends. Last, but not least, positive thoughts, pleasant experiences or music can distract you from pain or even allow you to forget it for a while.

These things are important for people who have chronic pain. They show us that our experience of pain can be influenced by what our brain associates with it. For instance, fear of pain plays an important role. Understanding what causes chronic pain may also help people to cope with it better.