What exactly is pain?
The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”.
This definition confirms that pain has both sensory and emotional features, and that it may or may not be associated with damage to one or more parts of our body.
Without pain, we would not know to pull our hand out of the fire or whether or not our skin has been cut by a sharp object. So, acute pain is essential for survival and wellbeing. Chronic pain may also be helpful. For example, for someone who has coronary heart disease, the experience of recurrent or ongoing chest pain can be a vital sign to seek investigation and treatment by a heart specialist.
Not all chronic pain is helpful however. Millions of people around the world experience chronic pain and for most of them it is not only a very disturbing burden, but also the greatest impediment to a good quality of life.
The sensation of pain
When we are injured, say in the hand or leg, local chemical changes take place as an effect of the injury. These are translated into electric messages that travel through our nervous system to a part of the brain called the “sensory cortex”. Here is where we sense the location and strength of the pain.
Although we know that pain signals travel through specific nervous pathways, we also know that none of these pathways are exclusively for pain. All sorts of other sensations, e.g. hot or cold, touch or pressure, are also carried along the same pathways. These help us form an integrated sense of our bodies.
An important relay station along the way of feeling pain and other bodily senses is found at the base of our brain, in a structure called the “Peri-aqueductal Grey” (PAG). This is a place within the nervous system where the various sensations we receive begin to become increasingly integrated to help form a full picture of our body. Pain, therefore, is one of many sensations that contribute to our experience of our body.
As well as sensations, emotions also contribute to our experience of our body. This is because PAG also sends signals to the emotional part of the brain. This helps explain why the IASP definition of pain refers to pain as both a sensory and emotional experience. Emotions seem to be particularly important in chronic pain.
The feelings of pain and anxiety
There are two pathways that send messages of pain and other sensations from PAG. As mentioned, one goes all the way up to the sensory part of the brain. The other goes deep into the emotional part. This is where the emotional aspects of pain are formed, so that two people with the same injury and intensity of pain may experience it differently; one might find it more upsetting than the other, or more disabling than the other. For example, if a patient has reason to be more anxious about their circumstances and their future, this may mean that their pain is more upsetting and has a more disruptive effect on their lives than for others.
Like pain, anxiety is essential for survival. Anxiety may be manifested as physical tension, restlessness, sense of threat and vulnerability, or worry about the future (immediate, medium and long-term future). It is essential that we can feel anxious so that we may anticipate threats to our physical, mental and social future. Also, like pain, anxiety can be acute or chronic. Finally, like pain, chronic anxiety may be helpful or unhelpful.
Unfortunately, like chronic pain, millions of people around the world experience chronic anxiety and for most of these it is also not only a very disturbing burden, but the greatest impediment to a good quality of life. Because chronic anxiety and chronic pain are all too common, they often occur together in the same person, and thus make it all the worse for the patient.
The anxiety and pain ‘elevator’
Pain can increase anxiety, and anxiety can increase pain. Both at the level of the PAG and at the level of the emotional part of the brain, pain and anxiety chemicals and pathways overlap.
It’s easy to understand how pain, or the threat of pain, can cause us to worry, tense up and generally feel anxious. It is more difficult to understand how anxiety can cause us to feel more pain, especially when there is a well-understood cause for our pain, such as a broken leg, recent surgery or an injured nerve. However, we know a lot about how anxiety can exacerbate pain and, more generally, how emotions can influence pain.
We know that, as well as pain and other sensations travelling through the PAG to the emotional brain, there are also nervous pathways carrying messages from the emotional brain back down to the hurting part of the body. These pathways are called the Descending Modulating Pathways and can alter the intensity of pain. Emotions, including anxiety, travelling through the Descending Modulating Pathways may increase or reduce pain, much as an elevator goes up and down. However, unlike an elevator, where we can press a button for the precise level we want to go to, in these pathways we do not have precise control.
In some chronic pain states, we can say that anxiety has disabled our capacity to control precisely the level of our pain, and our pain elevator is stuck on the top floor; or that is has overcharged the elevator mechanism, so that pain goes up and down out of control.
Chronic pain and anxiety disorders
Pain is by far the most common reason why patients see their doctors. On the other hand, anxiety and its disorders are the most frequent medical conditions to affect new patients each year. Therefore, as both pain symptoms and anxiety disorders are common, it is not surprising that the two often occur together. When this happens, they can create a vicious cycle where each is increasing the other – and preventing the reduction or recovery from both.
What does this mean for treatment?
In clinical practice, unfortunately, the presence of pain all too often blinds patients and their doctors to the presence of anxiety disorders, and attention is focused exclusively on pain.
One of the major risks of neglecting anxiety and it disorders in chronic pain is prolonging suffering by prescribing high and harmful doses of pain medications. Amongst these, opioid medications have caused concern, because they can lead to physical addiction and a paradoxical effect called “opioid hyperalgesia”, whereby the medication that had been prescribed to reduce pain is actually leading to increased pain.1
So, whilst it is always important to investigate and treat pain thoroughly, it is essential not to neglect anxiety when it is present and treat both. Otherwise treatment is not optimised and avoidable complications occur that can lead to patients suffering unnecessarily.
In this blog article, we have referred to anxiety and its disorders without specifying all the varieties of disorders. Similarly, we have not referred at all to the other group of emotional disorders that may interact badly with pain, namely the mood disorders. In clinical practice, it may be very important to differentiate these, as they may require different treatments.
Assessment by a psychiatrist with special interest in pain can help produce best clinical outcomes in chronic pain, including reduction or relief of pain or coping with pain.