In the last blog Dr Francis reviewed the evidence showing that tissue damage in the spine is a normal sign of ageing, and therefore cannot adequately account for people who experience on-going chronic pain. Dr Francis also spoke about pain as an output of the brain in response to perceived danger, and that factors other than tissue damage which the brain considers dangerous can create and modulate pain.
In today’s blog Dr Francis consider in more detail why the brain creates pain, how this is adaptive response in acute pain but less so in chronic pain, and how emotions may come to signal danger and trigger ‘pain neural pathways’ in the brains of people exposed to adverse childhood experiences.
A new definition of pain: a protective response of the brain to perceived danger
Historically pain has been defined by its unpleasantness, and no doubt for pain sufferers this seems wholly appropriate because ultimately it hurts! However, pain is actually a protective response by the brain to keep the body safe from perceived danger. It is a healthy and adaptive way of ensuring a species survival much in the same way that fear is (something we will touch on later). Indeed, consider the fact that those few people who are born without the ability to experience pain (‘congenital insensitivity’) typically die young, as they have no way of knowing something is wrong with their bodies and thus when they need to rest and/or seek help.
Pain is therefore always about protection - it is not about the actual state or damage to body tissues, but about potential danger to the body as predicted by the brain.
The problem begins however when the brain creates pain in the absence of any obvious danger to the body. This is what we observe in chronic pain. It is as if the brain is operating on an excessive safety first principle and predicts danger readily without obvious evidence. If the brain is perceiving danger that is not related to tissue damage (‘noxious stimuli’), then what are the sources of this danger and how can such non-noxious stimuli (i.e. stimuli that do not cause tissue damage) cause pain?
Pain neural pathways
Neural pathways are the ‘motorways of the brain’, carrying electrical impulses like cars along millions of nerve cells to enable us to perform all of our behaviour. When we learn to ride a bike, memorise our times tables or when we walk, the brain creates neural pathways in order for us to do these things. Dr Howard Schubiner, a medical internist and researcher in the field of chronic pain says neural pathways are also formed in acute pain following an injury. Pain effectively becomes ‘learned’ by the brain and central nervous system, and even when the damaged tissue has healed following acute injury, the pain neural pathways remain present.
Most importantly, these pain neural pathways can be activated, and thereby re-trigger pain chronically, by any non-noxious stimuli. Dr Schubiner says that feelings and ‘emotional injuries’ can act as potent non-noxious stimuli if such emotions generate anxiety and thus are perceived as ‘dangerous’ by the individual. From this perspective it is not too big a leap to see therefore how individuals who are prone to fear and become anxious in response to certain emotions are at risk of developing chronic pain through activation of pain neural pathways. Although fear and anxiety are usually considered an outcome of pain itself (i.e. a fear of being in pain), for many chronic pain sufferers, fear and anxiety have usually preceded the onset of their pain and relate to stressful life events in the present and in the past.
Adverse childhood experiences in chronic pain
Adverse childhood experiences (ACE) such as abuse, neglect, or having a parent with a mental health problem have been found to significantly increase people's risk of well-defined physical illnesses such as stroke, diabetes and heart disease, as well as chronic pain (Anda & Felitti, 2003). Whilst stressful experiences are a common occurrence in life for every person, patients with chronic pain often report experiencing a greater number of ACE than the general population. The greater the number of ACE the greater the risk of developing physical diseases and pain (Felitti et al., 1998).
How does exposure to such experiences in childhood increase the risk of physical disease and pain later in life?
When subjected to these kinds of frightening experiences, children appear to acquire an over-developed fear response and their central nervous system becomes sensitised to fear (McFarlane, 2010). Fear responses are a normal and a vital part of our species ability to survive and deal with threats to our safety; fear like pain then is another output of the brain that is geared towards protection when the brain perceives danger. As an example of fear’s usefulness, if crossing the road and you see an oncoming car, this is registered by the brain as danger and a fear response is triggered. The resultant bodily changes allow you to deal with the threat; these changes include an increase heart rate, breathing and muscle tension (often called the ‘fight or flight’ response) mobilise you to jump out of the way before you are squashed! But in those individuals who have experienced ACE this adaptive fear system appears to be on 'overdrive' and activated even when threats are not present - can you see how in both instances the brain is responding to perceived danger by creating outputs of fear and
pain to ensure action is taken to protect the body from harm?
Importantly, whilst threats may generate fear when located externally in the environment (such as an oncoming car or a physically abusive father), threats may also generate anxiety when located internally or inside oneself such as painful feelings and emotions. Why are feelings registered as a danger by the brains of some people who are exposed to ACE? The answer seems to lie in the importance of maintaining bonds with caregivers in childhood.
Attachment theory and emotions
Attachment theory (Bowlby, 1969; Ainsworth, Blehar, Waters & Wall, 1978) says that a close bond between a child and caregiver is vital for the child to survive and thrive. Where children experience ACE, they are likely to experience many painful feelings such as grief, rage, sadness and guilt. A vital function of a caregiver is the containment of a child’s feelings, such that they come to learn how to contain and regulate their own emotions and use them in healthy ways. However, in the context of an insecure bond, the child’s feelings are likely to create anxiety within the caregiver and may be met with hostility (imagine the child who cries with sadness and is met with criticism for being ‘weak’ by their father) or may even be ignored. The child’s feelings in this instance are therefore not contained, and the child must come to develop ways to hide and disown their feelings from themselves and their caregivers to avoid further threats to an already fraught bond. When these children do experience feelings, anxiety adaptively serves as a danger signal mobilising the child to use strategies to hide their feelings and keep their caregivers contented. These strategies are often called psychological defences because they serve to defend the person from emotional pain.
Over time these defences against feelings may begin to form into specific personality traits which are often characteristic of patients experiencing chronic pain: people pleasing; perfectionistic and setting high standards for oneself; a tendency to be self critical; prioritising others; and excessively caring for others at the expense of one’s own needs. Such traits can later become a source of difficulty for the adult. Take for instance an individual who experiences the breakdown of their marriage. Rather than face painful feelings of grief and anger associated with this loss, such individuals may resort to being self-critical as a way to cover up their angry feelings towards their partner. They may also try to win the affections back of their partner by trying to ‘be better’ and working harder to ‘be good enough’. In turn they may then end up experiencing anxiety and depression because of their self-criticism and the pressure they place upon themselves. This marriage breakdown may mirror a similar earlier experience for this person, such as experiencing the neglect of a critical and abusive caregiver.
Whilst the above scenario is factitious, it is typical of those patients I have worked with who suffer chronic pain. The majority of these patients typically report multiple stressful life events preceding their pain, but often do not make a link between stressful life events, painful emotions, anxiety and their chronic pain. However, it is precisely these stressful life events which triggering emotional pain and danger signals within the individual that can lead the brain to activate pain neural pathways leading to chronic pain.
Bringing it all together
It is time to try and pull the many different strands together of what I have covered in this blog.
Structural damage to the spine is a normal part of ageing in healthy adults, and cannot account for the presence of chronic back pain. Medical treatments of chronic back pain, such as surgery or opioids, are largely ineffective because they do not treat the underlying cause, which fundamentally relate to the brain’s perceptions of safety and danger, and the impact that ‘feared’ emotions have on activating pain neural pathways. Pain neural pathways may initially develop in response to some kind of acute physical injury, but remain present even when tissue damage has healed. Emotional injuries which generate anxiety can activate these pain neural pathways and thereby trigger pain in the absence of physical injury. Emotions can come to be experienced as dangerous by those exposed to ACE because feelings may have represented a threat to an already insecure bond to their caregivers. Although such individuals may have developed adaptive strategies to avoid their feelings in childhood, these strategies can later become problematic. In the absence of an emotional outlet, the ever increasing anxiety being generated by repressed feelings comes to be perceived as too much of a danger to safety by the brain, resulting in the activation of pain neural pathways and the creation of chronic pain and other physical bodily complaints such as Irritable Bowel Syndrome (IBS) which often presents alongside chronic pain.
So now we have some sense of what may be causing and maintaining chronic pain, what then can be done to treat it and improve people’s lives and wellbeing?
In the next and final blog Dr Francis discusses how psychological treatments focussing on reducing the brain’s perception of emotions as threats can help reduce, and in some cases eliminate, chronic pain.