What is pain?

Definition

The definition of pain, according to the International Association for the Study of Pain, is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Why do we experience pain?

Pain is extremely important for our survival. It's like our own personal warning bell that protects us and helps us avoid objects or situations that are - or may be - dangerous. When our brain registers pain, we tend to stop doing whatever caused the pain, For example, if we accidentally touch a hot plate, the pain makes us aware of the fact that something is wrong so that we can remove the hand and avoid a serious injury. This type of pain is called acute pain - it typically occurs after some kind of injury and decreases as the injury heals. For this reason, it is also relatively easy to treat. Chronic pain, however, doesn't serve the same function, but we'll get to that later.

An individual and subjective experience

Pain is an individual and subjective sensory experience. If several people were to sustain the exact same injury, they would all experience pain in different ways. One might feel more pain than the others, and another person might find it more difficult to deal with the pain than the rest. Neither of these people would be right or wrong - they simply have different pain experiences.

A person's pain experience depends on a large number of factors, for example:

• Previous pain experience - Are you often in pain? Have you been through something that caused severe pain, such as childbirth or serious injuries? When in pain, you subconsciously compare it to previous pain experiences. 
• Co-existing conditions such as anxiety and mood disorders or other painful conditions may worsen your pain,
• Negative thoughts or feelings such as fear and anxiety worsen the pain. This, in turn, increases the fear and the anxiety and leads to a negative circle.
• Perceived control over the situation. Studies have shown that people who feel like they have the ability to affect their situation (at least to a certain extent) experience less pain. Conversely, those who feel helpless and hopeless tend to experience more pain.  

A person's pain experience will also vary from one day to another. You will likely experience more pain if you are stressed, if you haven't slept well, or if you aren't feeling well emotionally. The same goes if you have a migraine or the flu - any pain that you are subjected to right then will probably feel stronger or more unbearable than usual.

Another important thing to remember about pain is that everyone shows it in different ways, which means that there is no way to assess how much pain a person is in just by looking at them. Some people grimace, frown, wince or cry when they are in pain, while others become introverted and suffer in silence. The amount of pain that feels acceptable and manageable also varies from one person to another. There is no right or wrong here - what matters is your own experience. If you rate your pain as an 8 on a scale from 0 to 10, it's an 8, period. No one has the right to say otherwise. However, most people who suffer from chronic pain have experienced, at one time or another, that others don't believe that they are in severe pain since they usually don't show it as much as others (which is often the case when you become used to living with crippling pain). The people that don't believe them can be friends, family members or co-coworkers, but also doctors or nurses. For this reason, it's vital that people understand that pain is individual and subjective. 

The pain pathway

In order to understand how we can manage or alleviate our pain, it is useful to have a basic understanding of the processes within the body that lead to the perception of pain.

The pathway involves three main locations: the site of the injury, the spinal cord, and the brain. As you can see in the picture below, spinal nerves connect the brain and the spinal cord, while peripheral nerves connect the spinal cord to the rest of the body (skin, muscles, inner organs, etc.). 

At the end of our peripheral nerve cells, we have a type of sensory receptors called nociceptors that detect damaging or potentially damaging stimuli in our surroundings, e.g. heat or pressure. In order for the nociceptors to be activated, the stimulus must reach a certain level of intensity (a threshold). 

When the nociceptors are activated, they send pain signals to the spinal cord through the peripheral nerves. In the spinal cord, the signals are transmitted from one nerve cell to another, and then continue to the brain through the spinal nerves.

In the brain, the signals reach a structure called the thalamus which works like a kind of sorting station. From here, they are directed to the different parts of the brain that are involved in pain processing: the somatosensory cortex (= the physical sensation of pain), the prefrontal cortex (= thinking processes), and the limbic system (= emotions). These brain structures register and interpret the signals, and the result is a multidimensional pain experience. 

Different types of pain

There are different ways of classifying pain, but the most widely accepted categories are nociceptive, neuropathic, and nociplastic pain. Even though many painful conditions mostly fall into one category or another, a lot of people experience a mix of two, or even all three types. Understanding what kind of pain you suffer from can be helpful in deciding what treatments and medications suit you best.

Nociceptive pain is the most common type of pain that people experience. It is caused by injury or damage (or even potential damage) to body tissues such as the skin, muscles, bones, joints, and internal organs. Nociceptive pain can be aching, sharp, or throbbing. It can be constant or intermittent, and often changes with movement, position, and load. Common examples of this type of pain include sprains, fractures, cuts, burns, tumors, inflammatory conditions, and postoperative pain.

Neuropathic pain is caused by injury or disease of nerve tissue (nerves, spinal cord, or brain). It is often described as a stabbing, burning or shooting sensation, and can be accompanied  by feelings of numbness and tingling, or a loss of sensation. People who suffer from neuropathic pain may be hypersensitive to painful stimuli (e.g. movement, pressure, heat or cold), and may even feel pain from stimuli that normally aren't painful at all, such as a light touch. Neuropathic pain is more likely to lead to chronic pain since nerve tissue doesn't heal well, so it is important to get the right treatment as soon as possible. Common examples of neuropathic pain include spinal cord injuries, spinal disc herniation, carpal tunnel syndrome, sciatica, impingement or diabetes neuropathy.

Nociplastic pain is a new category, defined by the IASP as pain that "arises from altered nociception, despite no clear evidence of actual or potential tissue damage... or evidence for disease or lesion". In simpler terms, pain signals are activated for no apparent reason. Two of the most common examples are fibromyalgia and irritable bowel syndrome. Nociplastic pain is often described as primary pain, which means that the pain itself is the problem, and not just a symptom of an underlying condition. It is also believed that nociplastic pain may arise from a history of other types of pain. Regardless of what may cause it, the introduction of this new type of pain is highly validating for everyone who suffers from unexplained chronic pain.