Recognition of the links between PTSD and chronic pain have been well established. The complex mechanisms and factors which predispose and perpetuate these inter-related conditions continue to be investigated, however a shared vulnerability, mutual maintenance and the role of avoidance common to both appear to offer explanatory models (Murphy et al., 2022). In clinical settings, identification of patients who meet diagnosis for both chronic pain and PTSD is a priority. Optimal treatment pathways remain a clinical challenge requiring further research.
Prevalence
Prevalence statistics amongst veterans are more readily available. Among those with PTSD, Murphy et al., (2022) report an estimated 25-80% may also experience chronic pain, together with higher levels of pain intensity, catastrophising, disability and health care utilisation. For those with chronic pain as a primary diagnosis 9% experience comorbid PTSD, increasing to 20% for those with chronic widespread pain (Murphy et al., 2022). Prevalence information for individuals in primary care or pain clinics is more difficult to ascertain as PTSD prevalence data is not routinely collected. A recent quality initiative to document prior trauma exposure was undertaken at a Victorian multidisciplinary pain clinic. Patients were not directly asked about their trauma histories, but any reference to traumatic events was noted during the multidisciplinary assessment on a trauma events checklist. Up to 35% of presenting patients had PTSD, with an even greater number referring to previous traumatic events (Lydall-Smith et al., 2020). Given the method of data collection, this is likely to be an underestimation.
Theories
Murphy et al., (2022) proffer three possible theoretical contributions to understanding the co-occurrence of PTSD and persistent pain. The first is the shared vulnerability model which suggests that anxiety sensitivity and a fear response to physiological sensations predisposes to both conditions. There is also some support for a potential role of central sensitisation as an underlying mechanism of shared vulnerability. Central sensitisation is an amplification of neural signalling in the central nervous system. It is noteworthy that one potential contributor to developing central sensitisation is childhood adversity, which is also common to the development of PTSD. Importantly, it is the impact of the trauma that is related in the development of chronic pain. In Cognitive Processing Therapy (CPT), the impact of the trauma also holds clinical significance. Further complicating this process are the shared neurobiological factors that underlie chronic pain and PTSD and are related to mediating emotional distress and physiological threat. There is increasing research interest into the longer term mental and physical health impacts of Adverse Childhood Events, which shape the development of both physiological and emotional responses to stress (Finlay et al., 2022).
The mutual maintenance model considers the ways in which both conditions perpetuate each other. Similarities in the way patients with both conditions appraise and attend to threatening and painful stimuli, are sensitive to anxiety and tend to relate pain as a reminder of trauma together results in the adoption of avoidance to minimise both pain and trauma symptoms. This links strongly to fear-avoidance models where hypervigilance, fear and behavioural avoidance are magnified, with increased distress, secondary deconditioning and decreased functioning. For example, patients with persistent pain have heightened psychophysiological responses such as heart rate and muscle tension to both trauma-related and environmental stimuli. Liedl & Knaevelsrud (2008) report that those who experienced a trauma with physical injury were eight times more likely to develop PTSD. In addition, cognitive appraisal of both the trauma and the experience of chronic pain play a crucial role in the severity and maintenance of both conditions, particularly where avoidance is a mutual coping strategy.
Addressing hypervigilance and safety behaviours is also a shared requirement. Beliefs regarding safety following a trauma result in an elevated state of arousal and attempts to minimise any further occurrence. Similarly, pain patients also exhibit heightened arousal states and behaviours such as body scanning contribute to an increased awareness of any somatic irregularity.
Treatment
Exposure strategies common to PTSD treatment models target the avoidance by assisting patients to process their traumatic and feared experiences so they are able to reinterpret the situation and see it as part of their past. Similarly, exposure strategies are also helpful in treating or managing persistent pain where patients are encouraged to engage in physical activities previously avoided due to the fear of activating more pain or re-injury. This is achieved by allowing them to gradually focus and cope with uncomfortable physiological sensations and reduce fear avoidance beliefs. Given these overlapping symptom profiles, it is essential that therapy initially comprises psychoeducation regarding the development and maintenance of PTSD and chronic pain. Following this, several treatment modalities have been highlighted by Murphy and colleagues (2022).
The first and most common is the sequential model (Angelakis et al., 2020) where the Pain and PTSD conditions are addressed separately and in a linear fashion. This has been demonstrated with other comorbidities such as depression, eating disorders and substance use disorders. Murphy et al, (2022) suggest there is limited evidence advising which condition to prioritise, whereas Angelakis indicated a benefit in addressing PTSD prior to depression. Where no clear guidance is present, client preference or identification of which disorder is most distressing / disabling can be the criteria. Complications include the remaining disorder worsening or interfering with that being treated and referral to the subsequent treatment being interrupted, or not proceeding due to system or client factors.
The parallel model treats each disorder concurrently with a provider or team addressing each area of care. However, these treatments usually operate independently without a unified whole person treatment plan which limits efficiency and the unified focus on shared factors. Complications include mixed messages, differing priorities and emphases. In addition, the multiple appointments and homework may be overwhelming both physically and emotionally impacting successful outcomes for either or both conditions.
A combined or integrated model addresses pain and PTSD simultaneously with a single treatment team who hold expertise in both conditions. Whilst not broadly available, it best encompasses the biopsychosocial, whole person framework with coordinated care. Treatment in this model relies on evidence based therapies and cognitive behavioural principles with demonstrated effectiveness in both conditions, emphasising a focus on the shared role of fear-avoidance in both pain and PTSD. Some recent studies indicate this treatment pathway is promising but future research is required to better understand effectiveness and potential for implementation. One option may be to formalise offering concurrent PTSD treatment in interdisciplinary pain programs. Another may be to further develop the 12 session integrated treatment trialled by Otis and colleagues (2009) using components of CPT for PTSD and CBT for pain management. Given the high prevalence of comorbidity in these two conditions, further research to better guide intervention is warranted.
References
Angelakis, S., Weber, N., & Nixon, R.D.V. (2020) Comorbid posttraumatic stress disorder and major depressive disorder: The usefulness of a sequential treatment approach within a randomised design. Journal of Anxiety Disorders, 76
Finlay.S., Roth, C., Zimsen, T., Bridson, T.L., Sarnyai, Z., & McDermott, B. (2022) Adverse Childhood Experiences and Allostatic Load: A Systematic Review. Neuroscience and Biobehavioural Reviews, 136.
Liedl, A., & Knaeelsrud, C. (2008) Chronic Pain & PTSD: the Perpetual Avoidance Model and its treatment implication. Torture 18(2)
Lydall-Smith, S., Bowler, M., Funke, A., Alexiou, T., Griffiths, K., White, B., & Field, D. (2020) Poster presented to the New Zealand Pain Conference.
Murphy, J.L., Driscoll, M.A., Odom, A.S. & Hadlandsmyth, K. (2022) Post Traumatic Stress Disorder & Chronic Pain. PTSD Research Quarterly 33(2)
Otis, J.D., Keane, T.M., & Kerns, R.D (2003) An examination of the relationship between chronic pain and post-traumatic stress disorder. Journal of Rehabilitation Research and Development 40(5), 397-405