Posttraumatic stress disorder (PTSD) and chronic pain disorder are highly comorbid.1,2
The literature indicates a high degree of co-occurrence between pain and PTSD, regardless of whether the pain is being assessed in patients with PTSD or PTSD is being assessed in patients with chronic pain. Also, they may interact in such a way as to negatively affect the course and outcome of treatment of either disorder.3
The high comorbidity between these disorders has been postulated as being due to either shared vulnerability or mutual maintenance.1,2
PTSD symptoms are associated with greater reporting of physical health problems and symptoms, and also are strongly associated with current pain, overall pain ratings, and pain-related disability.1,4-8
Evidence suggests that PTSD symptoms and pain frequently co-occur on an acute level, yet this association also appears to hold in cases where pain persists beyond the acute phase.1
In one of the first studies looking at the co-occurrence of PTSD and chronic pain, White and Faustman9
reported that 1 in 5 military veterans with PTSD developed chronic pain. Beckham and colleagues4
investigated chronic pain patterns in Vietnam veterans with PTSD and observed that 80% reported chronic pain. McFarlane and co-authors10
investigated the reporting of physical complaints in a sample of firefighters with and without PTSD and found statistically higher rates of musculoskeletal pain (primarily in the back) in those with PTSD, as compared with 21% of those without PTSD.
Also, studies have shown that PTSD symptoms tend to be elevated in patients with chronic pain and fibromyalgia.8,11,12
It appears that between 10% and 50% of patients receiving tertiary-care treatment for chronic pain and related conditions have symptoms that meet criteria for PTSD, as compared with approximately 8% of the population in general.1
For example, approximately 10% of patients referred to a pain clinic met criteria for PTSD.13
The prevalence of PTSD increased when the pain problem directly resulted from a traumatic event.3
Rates of PTSD in patients for which pain is secondary to a motor vehicle accident range from 30% to 50%.3,14-16
PTSD symptoms in individuals who experience work-related injury were 34.7%.17
High rates of PTSD (45%) were reported in hospitalized burn patients 12 months post-injury.18
PTSD-like symptoms were found to be more prevalent in fibromyalgia-syndrome patients.8,11
PTSD subjects also reported more pain, lower quality of life, and more functional impairment, and suffered more psychological distress than PTSD patients not having fibromyalgia syndrome.8
These findings indicate that pain symptoms and chronic pain are prevalent in patients with PTSD and that PTSD symptoms are common in patients with chronic pain.
Despite this relatively large literature on the co-occurrence of pain symptoms and PTSD, we know of no data demonstrating actual differences in pain medication use among those with PTSD versus those without. If such a difference exists, it would be critical to demonstrate this potentially more objective measure, given the complex issues of symptom reporting. Furthermore, it raises potential questions about the role of analgesic use as self-medication in patients with PTSD.
There is evidence that endogenous opioids play a role during the human stress response;19
the endogenous opiate system has therefore been implicated in psychobiological models of PTSD-maintenance.20,21
Although experimental data on opioid mechanisms in PTSD are scarce, a number of investigators have suggested that abnormalities in the endogenous opioid system may be important in PTSD symptomatology.22-24
It has been shown that PTSD patients exhibit lower pain thresholds, lower β-endorphin levels, and decreased production and release of methionineenkephalin and, possibly, stress-induced analgesia.19
Beyond the obvious pain-reducing qualities of opiates, these medications have direct and potent inhibitory effects on neurological systems known to be important for the development of PTSD. For example, Saxe et al.23
showed that morphine administration reduced PTSD symptoms over a 6-month period in children with burn-related pain.
Because of the high degree of comorbidity between chronic pain disorders and PTSD, we hypothesized that pain medication would be prescribed more for patients with PTSD than those without PTSD among an outpatient sample. An additional prediction is that the symptom clusters of numbing/avoidance might be more closely associated with pain medication use than are other symptom clusters. In fact, we find that all PTSD symptom clusters are highly associated with increased pain medication use. Interestingly, the cluster of hyperarousal appears to be the most highly associated with analgesic prescription rates.