Somatoform Pain Disorder: Pre-accident psychological history and vulnerability and the BUT FOR test in the absence of a trigger

Somatoform disorder (SD) is defined as physical symptoms suggestive of a medical condition which are unexplained by an underlying disease or mental disorder. Somatoform symptoms are common, and mild ones, such as stress as a trigger for migraine or butterflies in the stomach before public speaking, are experienced by many people at some point in their life. SD is more frequently seen in women than in men, and usually manifests before the age of 25 years. While the condition is often chronic, there is also a milder form that resolves in around 50% of cases. It is often closely associated with comorbidities such as depression, anxiety, substance abuse and personality disorders. Although similar in presentation to factitious disorder and malingering, SD can be distinguished from these as the symptoms are not consciously produced.  

As the name suggests, in somatoform pain disorder, the main symptom is chronic pain. This often arises from an apparently minor injury and is far in excess of the level expected from such an event. It may also last for considerably longer than the normal healing time associated with such injuries. There is often an overlap with other somatoform disorders, so the existence of a purely pain-related syndrome is sometimes debated. Some form of physical trauma, such as a traffic accident or bone fracture, is thought to be a predisposing factor in around 50% of cases.  

It is now widely recognised that pain may have more than one cause. Furthermore, the experience of pain contains both physical and emotional aspects, and these cannot be separated. Patients with similar injuries may report widely differing pain levels and, while most patients will recover quickly, for some the pain will persist for many months after the original injury. It is not entirely clear why this happens but it has been hypothesised that some people possess a pre-existing psychological vulnerability that leaves them open to developing chronic pain.  

The human stress-coping mechanism, which determines an individual’s stress threshold, is primarily genetically determined, but can be individually shaped by psychosocial influences. Early adversity that affects this mechanism may result in dysfunction of the stress response system, which can lead to a long-term impairment in the ability to react to stress. This increases the likelihood that both physical and psychosocial factors may be important in the development of various conditions later in life and may result in somatisation. It is well-known that an accumulation of psychologically traumatic events in early life leads to an increased incidence of psychiatric illness in adulthood, and it is possible that this vulnerability extends to some physical conditions as well.  

Many studies have reported a connection between multiple adverse events in childhood and the later development of potentially somatoform disorders, such as complex regional pain syndrome and fibromyalgia. Adverse events are reported in a much higher proportion of patients with these types of conditions than in patients with medically explained chronic pain. One study found that around half of the participants with SD had significant anxiety or depression that was likely to be the cause of their illness. Furthermore, patients with a history of trauma report higher levels of pain, more accompanying symptoms and a higher use of analgesics. However, not all individuals report a history of traumatic events, so their presence is likely to be a predisposing factor rather than a causal event. It is also possible that their effect is cumulative, which is borne out by fact that many patients report multiple traumatic events, rather than one isolated incident.  

The ‘But For’ test is the indicator of causation in medical negligence cases. The basic principle of the test asks ‘but for the existence of x, would y have occurred?’. In many cases, this test is sufficient, but in some claims the circumstances surrounding the facts cannot be viewed in such a simplistic way. One important issue is that many patients have some form of illness before the alleged incident, and it is vital that the court is able to identify the natural history of the disease, in the absence of any other events, to determine what difference the alleged event may have made to the ultimate outcome.  

Previous legal rulings have established that in cases where the link between a possible causal factor and a disease has not been definitively established, it may be sufficient to show only that the contribution of the causal factor is likely to be material. Therefore, in pain cases where there is no obvious triggering event, the patient’s psychological history takes on a new relevance. In a patient with a significant history of trauma or psychological difficulties, it may be possible to argue that there was a pre-existing vulnerability to chronic pain, which would have been triggered sooner or later by a seemingly trivial event. Even where there is a potential triggering event, the patient’s post-incident history should also be carefully considered. If another event or injury is revealed, this may limit the extent of any claim, as it could be argued that the patient would probably have developed their condition sooner or later anyway.  

Further reading: 

Imbierowicz, K., & Egle, U. T. (2003). Childhood adversities in patients with fibromyalgia and somatoform pain disorder. European journal of pain (London, England), 7(2), 113–119. https://doi.org/10.1016/S1090-3801(02)00072-1 

Smith, J. K., & Józefowicz, R. F. (2012). Diagnosis and treatment of somatoform disorders. Neurology. Clinical practice, 2(2), 94–102. https://doi.org/10.1212/CPJ.0b013e31825a6183