What is chronic pain?

Definition

Chronic pain is a very complex, widely misunderstood, and - unfortunately - common condition. For a long time, there was no proper definition that defined or explained it. However, this changed when the World Health Organization (WHO) recently released the 11th edition of the International Classification of Diseases, also known as ICD-11. This version finally includes chronic pain and defines it as pain that lasts or recurs for more than 3 months.

According to ICD-11, chronic pain can be either primary or secondary.

Chronic primary pain is characterized by emotional distress and/or functional disability, and is not better accounted for by another condition. It is, therefore, seen as a disease in itself. Two very common examples in this group are irritable bowel syndrome (IBS) and fibromyalgia. It also includes chronic pain that used to be called "non-specific".

Chronic secondary pain is pain that, at least initially, can be conceived as a symptom of an underlying condition. It is organised into six different categories:

Chronic cancer-related pain: pain caused by cancer or its treatment (chemotherapy).
Chronic post surgical or post-traumatic pain: pain that develops or becomes more intense after surgery or accidental trauma and lasts for more than 3 months.
Chronic neuropathic pain: pain caused by an injury or disease that affects the nervous system (nerves).
Chronic secondary headache or orofacial pain, which includes headaches, dental pain and facial pain.
Chronic secondary visceral pain: pain that originates from injury, disease or inflammation in the internal organs in the neck/head/thoracic/abdominal/pelvic regions.
Chronic secondary musculoskeletal pain: pain in bones, joints and tendons arising from an underlying disease classified elsewhere.

Another thing that characterizes chronic pain is that it extends beyond the expected period of healing for an injury or disease, or the expected recovery time following surgery. Of course, the healing time varies somewhat between individuals and is affected by factors such as smoking, nutrition, and exercise - but if you're still in pain several months after an injury has healed, something isn't right.

Prevalence and statistics

Studies have shown that chronic pain affects approximately 30-50 % of the world population. However, the definition doesn't take into account the intensity of the pain, so these statistics include everything from mild to severe pain. If you look at the amount of people who suffer from moderate to severe pain, or pain that affects their daily lives, the prevalence will be about 8-10 % of the population, or 25 % of all of those with chronic pain.

Acute vs. chronic pain

A common misconception is that chronic pain is the same as acute pain except for the fact it lasts for a longer period of time. This is not true - in fact, this misconception is often the reason that people with chronic pain don't get the right treatment. Chronic pain is a lot more complex than acute pain. Trying to wrap your head around it requires a lot of time (as well as prior knowledge about human anatomy and the nervous system), but here are some of the main differences:

Acute pain is caused by some kind of illness or injury. Its purpose is to protect us, and it's extremely important for our survival. As the injury heals, the pain diminishes. Chronic pain, on the other hand, doesn't serve the same function. If it is caused by an injury, it usually persists long after the injury has healed. In this case, the pain is no longer protective or good for us. Instead, it becomes a problem that causes many physical, emotional and social consequences.
Acute pain is directly related to an injury or illness, e.g. a broken leg, kidney stones, or an open wound. Chronic pain may be caused by an injury that doesn't heal, but it is often very difficult to "explain" the intensity and the long duration of the pain. For example, it may have persisted a lot longer or be more severe than it should have. It's common to hear people say "you really shouldn't be in this much pain*. Unlike acute pain, there are a lot of different physiological, psychological and social factors that contribute to chronic pain.
Since acute pain is directly related to an illness or an injury, it's usually pretty easy to treat - you treat the injury that is causing the pain and/or treat the pain itself with painkillers. However, since chronic pain is such a complex problem, it's a lot more difficult to treat, and treating the injury and the pain with medications only will almost never be enough. Unfortunately, a huge amount of people who suffer from chronic pain don't get the treatment they need, many because of the lack of knowledge about what causes chronic pain and how to treat it, as well as the lack of specialized clinics and experienced healthcare providers,
When treating acute pain, the patient doesn't really have to do much since the treatment mainly consists of medications. When it comes to chronic pain, however, the patient must have an active role in the rehabilitation. In order to do that, they need to understand how chronic pain works so that they can understand why it's not treated in the same way as acute pain. Inadequate information usually leads to poor patient compliance (which means that the patient isn't likely to do as they are told), and often even a bad patient-provider relationship since the patient tends to feel like they aren't taken seriously, or that the healthcare providers don't care about them.