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Pain Is In The Brain

Pain is in a sense a mode of perception that is used by the body to tell us that something is wrong. In fact, pain can be considered as part of a collection of sensations such as sadness, nausea, fear and anxiety that we evolved as a self-protecting strategy. Evolving such sensations, therefore, became an important factor in our survival. The environment that we live in now is significantly different to the world we inhabited tens of thousands of years ago. And this disparity has consequently contributed towards an increase in many persistent or chronic conditions. Understanding pain requires a multifaceted approach in which biology (physiology), sociology (environment) and psychology (behaviour) must all be considered.


Pain is predominantly associated with structural biological damage (sprain, strain or fracture). However, as I will expand upon in this post you will begin to see the complex interplay that goes on within us all and how it elicits a sensation of pain. This more complex picture of pain is alluded to in the International Association for the Study of Pain’s definition of pain:


“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”


Pain is real and the symptoms associated with it are also real but structural damage does not necessarily have to be present. It does not have to come from tangible sources to be a valid problem. The sensation of pain is the conscious manifestation of a multitude of responses and is a process that occurs at a neuropsychological level. Unfortunately, much of the current healthcare system still relies on what is known as the ‘biomedical model’, this model focuses purely on the biological factors to the exclusion of psychological, environmental and social influences. Alternative models are now coming forwards as offering a better model for the treatment of pain. One such model is referred to as the ‘Bio-Psycho-Social model’, which offers a more nuanced and holistic approach towards the treatment of pain.


The Bio-Psycho-Social model was first introduced by George Engel in 1977. He argued that it was impossible to treat pain without looking at the entirety of the self. It, therefore, requires a deep inter-relational understanding of the three domains of biology, psychology and sociology. The premise is that pain and suffering tend to occur when the balance is lost between the three. It is also important to recognise that we are all unique biologically and psycho-socially. By understanding this it helps us recognise the individual's experiences of pain and the differing tolerances that individually we all have to it.


To better understand pain we now need to look at the mechanism that makes the pain sensations conscious to us, in other words, the nervous system. The nervous system is essentially a two-way information highway with nerves all over the body relaying information to the brain via the spinal cord by means of electrical impulses. The system within the nervous system that gathers information about pain is called ‘nociception’. The nervous system will make a judgement about what to refer up to the brain based on the context and quantity of information received, as well as the memory of past experiences and associated emotions such as fear, anxiety and avoidance. So the system has effectively a hierarchical system of stops and checks.


The information provided by nociception is not necessarily by itself enough to trigger the perception of pain. It is the brain that decides this ultimately, once it has processed the information. The brain can make an ongoing decision about how bad the injury is, what it needs to do to protect you, assess the long-term impacts and if it poses a threat to your long-term survival. Depending on this assessment the brain may cleverly depress your mood in order to slow you down as a protective measure. This works by not only reducing physical activity but also by signals to others that you are in need of help. This process is completely normal and the body will in due course heal itself and the brain's fear elements will be dispersed via a system known as ‘bioplasticity’.


This however raises one issue that currently affects some forty-three percent of the current UK adult population and that is persistent or chronic pain. In most circumstances any organic or structural damage should resolve within three months, if it does not it can then be classified as chronic in nature. So why then does the brain sometimes continue to register pain even when an injury has long since healed?


If pain persists and becomes established it can result in increased nervous system activation as a consequence there is an amplification of neural signalling that elicits pain hypersensitivity, basically, it turns up the volume and intensity on everything. This is a process that is referred to as ‘Central Sensitisation’. According to Dr Clifford Wololf central sensitisation has three principal effects; it lowers the firing threshold of nerves, it causes the after-effects of pain to linger and it causes incoming impulses from surrounding tissues to be seen as noxious even when they are not.


It is effectively a type of neurobiological ‘learnt behavioural disorder’ in which the brain misinterprets messages. The nervous system becomes sensitised to small stimuli with chronic pain. One consequence of this is that as the brain structures frequently remodel the longer you experience pain the more likely this will lead to changes in the brain’s structure, the most serious of which is atrophy (shrinkage) of ‘grey matter’ (the region of the brain involved in muscle and sensory control).


A shrinkage of the grey matter will cause people with chronic pain who are also stressed or depressed to exhibit a ‘withdrawal’ pattern of behaviour, they will become more guarded, socially isolated and also have disrupted sleep patterns. Social withdrawal, too, can become a vicious cycle because the more it develops, the more the feeling of pain and consequently the more withdrawn the individual becomes. Stress, depression and pain are all intimately intertwined.


I previously mentioned that there is a memory component to pain as well, that is even after the injury has healed the brain has etched and logged a neurosignature around the injury experience. So much so that triggering the memory (stress) can reignite the feeling of pain or result in elevated sympathetic nervous system activation (fight or flight). This effectively means that pain can lie dormant and can be re-felt under the right conditions. The more often pain is revisited the more habituated the brain becomes, it effectively becomes a ‘closed-loop or ‘default mode’ repetitive pathway.


Many factors in our environment can sensitise us and lower our pain threshold, chronic stress being one of the most common causes today. Unfortunately, once the pain signature has become established and has been influenced by all our negative life experiences, pain can become ingrained and cyclical and also move around the body (peripheral sensitisation). Examples of this process can be seen in conditions such as Irritable Bowel Syndrome (IBS), Fibromyalgia, Chronic Fatigue and Migraines.


Modern pressures and associative stresses can impact our sensitivity to pain, lowering pain thresholds and increasing pain sensations throughout the body. The treatment of pain, particularly long-term sufferers have not been helped with a purely biological model. The move towards a Bio-Psycho-Social model now offers a more holistic approach to pain management by not only treating the structural biological elements but also the social and psychological elements too. A move towards a more team-based approach one which deals with all three elements equally should go a long way towards stemming the current chronic pain epidemic that we are currently facing.