Ever had a car accident? Did you feel a rush of stress at that moment?
Whiplash is often the result of a car accident and causes a lot of physical and psychological stress. It might even cause a post-traumatic stress reaction and this stress reaction is related to poor long-term recovery in whiplash patients. A disturbed stress system is not the only possible consequence after a whiplash accident, dysfunctions of the pain system are also often present. More specifically patients with chronic whiplash have a hypersensitive nervous system and a dysfunctional internal pain inhibitory mechanism.
Are these effects on the stress system and the pain system unrelated or are they components of one integrated system?
To answer this question, we examined the stress response to a physical stressor (i.e. pain). Patients with chronic whiplash and healthy controls were subjected to an experiment to evaluate pain thresholds and pain inhibition. Meanwhile their autonomic functions (skin conductance, heart rate and heart rate variability parameters) were continuously monitored, to measure the autonomic response to acute pain.
We found that both patients with chronic whiplash and healthy controls had an autonomic response to acute pain. But we did not find any difference in this response in whiplash patients compared with healthy controls. This indicates that chronic WAD (whiplash associated disorder) patients and healthy controls show similar patterns of autonomic response to a painful stimulus. Furthermore, there was no relationship between the pain thresholds, pain inhibition and autonomic parameters. Yet whiplash patients who also suffered from post-traumatic stress reactions had a reduced autonomic reactivity to pain.
Our most interesting observation was that chronic whiplash patients do not show a distinctive autonomic stress response to acute pain. On the contrary, chronic whiplash patients have a similar response to healthy controls. The autonomic activity was also similar at rest. It seems that patients with chronic whiplash have normal autonomic activity and reactivity to acute pain, except for a subgroup experiencing post-traumatic stress who showed a blunted stress reaction. This suggests that a disturbance in the autonomic nervous system is not a general feature in chronic whiplash but instead might be a trait of a subgroup experiencing a prolonged state of stress after the impact event.
About Margot De Kooning
Margot is a doctoral researcher at Vrije Universiteit Brussel (Belgium) and the University of Antwerp (Belgium) and a member of Pain in Motion. She is interested in the role of central mechanism and their interaction in chronic unexplained pain. Her focus is on the stress response system, pain-motor interactions and sensorimotor integration and pain processing mechanisms in patients with whiplash associated disorders.
De Kooning M, Daenen L, Cras P, Gidron Y, Roussel N, & Nijs J (2013). Autonomic response to pain in patients with chronic whiplash associated disorders. Pain physician, 16 (3) PMID: 23703426