The relationship between psychiatric distress and pain is complex and dynamic. Greater posttraumatic stress symptom burden contributes to increased pain intensity (1, 2), however both posttraumatic stress and pain are differentially associated with age. Specifically, posttraumatic stress symptoms decrease with age (3, 4), whereas pain intensity tends to increase with age (5, 6). Although PTSD symptom distress may independently affect pain intensity, there is little evidence about how PTSD symptom distress affects pain severity across advancing age. The purpose of this study was to determine if and how posttraumatic stress disorder (PTSD) symptoms affected the relationship between age and pain.

Pain is a common presenting concern for older adults seeking medical treatment (7) and is associated with decreased quality of life (8), greater disability (9), increased risk for suicide (10), and significant health care costs (11). Most research examining pain has focused on chronic pain (i.e., pain lasting for >3 months), which is the most commonly reported health concern of post-9/11 military Veterans (12, 13). Although work with chronic pain is important, evaluating general pain intensity across any duration is an equally vital consideration given the increased likelihood of events (e.g., injuries related to falls, chronic conditions such as arthritis, surgeries) that can cause pain and are associated with advancing age (14, 15). Approximately 66% of Veterans report pain, with 9% reporting severe pain (12). This is likely related the increased risk for physical injury during combat or trainings as well as exposure to physical and environmental stressors that occur during military service. Congruently, pain is associated with a number of adjacent concerns, including mental health conditions, that contribute to increased health care burden (8).

PTSD similarly contributes to the substantial health care burden for many military Veterans. PTSD is the most prevalent mental health diagnosis and third most common service-connected disability among Veterans (16). Contrary to the typical trajectory of pain, the severity and prevalence of PTSD symptoms typically decline with age (3, 4), for which several potential contributing factors exist. Increased time since the trauma potentially allows individuals time to seek treatment, process and draw meaning from their traumatic experience, leading to reduced avoidance behaviors (17–19). Additionally, older adults generally endorse greater meaning in life, spirituality, and resilience, each of which have been demonstrated to buffer PTSD symptoms (20–22). Early mortality, associated with the high prevalence of comorbid chronic health conditions, may also contribute to the perception of decreased PTSD prevalence in older adults (23, 24).

Although both pain and PTSD symptoms can negatively affect quality of life, they can be particularly impairing when they co-occur. Chronic pain and PTSD have a reciprocal relationship, negatively and continuously affecting symptoms of the other, while cumulatively exacerbating negative functional outcomes (25–27). This reciprocal relationship falls under the biopsychosocial model of chronic pain that recognizes the dynamic interactions between biological, psychological, and social factors in the pain experience (28). There are numerous theories proposing mechanisms that explain the reciprocal relationship between PTSD and pain, including perceptual alterations of pain (e.g., anxiety sensitivity), coping, and cognitive changes [for a detailed review, please see (29)]. Investigations of pain and PTSD often evaluate the magnitude and directionality of the relationship (30–32). For example, Veterans with PTSD report greater pain intensity than Veterans without PTSD (26, 33). Additionally, the relationship between PTSD and chronic pain has been shown to be fairly consistent over a 3 year period among young adult military personnel (34). However, little is known about the effect of age on the relationship between PTSD and pain. A recent meta-analysis reported that the relationship between PTSD and pain remains important at older ages in civilian samples (35). Considering the high prevalence of pain and PTSD in Veteran samples, this is an especially important question to evaluate within this population.

In summary, PTSD symptom distress may be an important factor to consider in the relationship between age and pain. Pain and PTSD symptoms are differentially associated with age; pain intensity increases with age, whereas PTSD symptoms decline with age. Given that PTSD is often associated with increased pain, it is likely that PTSD symptoms affect pain intensity ratings at older ages. The purpose of the present analysis was to understand how PTSD symptom severity and age interact to affect pain intensity. It was hypothesized that age would be positively associated with pain intensity and negatively correlated with PTSD symptom severity. Second, it was hypothesized that PTSD symptom severity would exacerbate the association between age and pain intensity. These preliminary analyses inform whether addressing PTSD symptoms represent an additional avenue of treatment to help alleviate experience of pain, specifically as Veterans age and the incidence of pain increases.

Data were collected as part of the VISN 6 Mental Illness, Research, Education and Clinical Center’s (MIRECC) Study of Post-Deployment Mental Health Longitudinal Follow Up (PDMH-L). PDMH-L is the longitudinal arm of the baseline multisite PDMH study (36). The purpose of the PDMH studies is to better understand the effect of deployment on the physical and mental health of service members and Veterans. These studies gather clinical interviews, biological samples, questionnaires, physical measurements, and data from the electronic health record. The study was approved by the respective IRBs at each site. Participants were reimbursed for their time and travel.

Participants were 450 post-9/11 Veterans (80% male) between the ages of 33 and 78 (Table 1), normally distributed within descriptive categories of younger adults (16% ages 18–39), middle-aged adults (64% ages 40–59), and older adults (19% ages 60+). Most participants identified as White (49%) or Black (48%) with some college education (M_years = 14.36). The majority of participants (95%) reported at least one combat deployment during their military service. The sample typically endorsed PTSD symptoms considered to be well below threshold [i.e., > 33; (40)] for diagnosis (M = 21.97; SD = 19.29). Approximately one fifth of the sample met full diagnostic criteria for a current PTSD diagnosis (n = 88; 19.64%) according to the SCID-IV (43). Most participants endorsed chronic pain (n = 373, 84.19%) evaluated as endorsing pain on item 10 of the BPI persisting greater than 3 months.

As presented in Table 2, pain intensity was significantly, positively correlated with age (r = 0.11, p = 0.021) and PTSD symptoms (r = 0.36, p < 0.001). PTSD symptoms were significantly, negatively correlated with age (r = −0.17, p < 0.001). There were no significant sex differences on pain intensity (p = 0.073), pain interference (p = 0.510), or PCL-5 scores (p = 0.832). However, men (M = 51.25) were reliably older than women (M = 48.52) in this sample, t (448) = 2.35, p = 0.019.

As presented in Table 3, the omnibus model was statistically significant, R² = 0.20, p < 0.001. In Step 1, there were significant main effects of age, B = 0.04, p < 0.001, CI [0.02, 0.06], and posttraumatic stress symptoms, B = 0.05, p < 0.001, CI[0.03, 0.06] on pain intensity beyond covariates.

The interaction effect between age and posttraumatic stress symptoms in Step 2 was significant, ΔR² = 0.01; F (1,439) = 4.39, p = 0.036, CI [0.001, 0.002], demonstrating that the effect of age on pain was enhanced as PTSD symptom severity increased. Johnson-Neyman analysis indicated that the effect of age on pain severity was significant when PCL-5 scores were above 14.72 (Figure 1). Of note, age and PTSD symptoms were used as continuous variables for statistical analyses and were grouped only for illustration purposes in the figure. Pain scores were exacerbated with increasing PCL-5 scores (Figure 2). These effects were strongest among the oldest participants.

The results of the present study demonstrate that the interaction between PTSD symptoms and age is important for understanding pain intensity in Veterans. As expected, pain intensity increased with age and PTSD symptoms, and PTSD symptoms declined with age (Table 2). However, the effect of age on pain was exacerbated as self-reported PTSD symptoms increased. Specifically, scores of 15 or greater on the PCL-5 were associated with increasing effects of age on pain intensity. A score of 15 is below the threshold (> 33) generally considered clinically significant (40); however, these findings emphasize that even low levels of self-reported PTSD symptoms can begin to affect health.

These results also demonstrate that PTSD symptoms contribute to higher pain ratings in older individuals. This is particularly important, as Iraq and Afghanistan-era Veterans represent a large aging cohort experiencing a high prevalence of both PTSD symptoms and pain conditions (49, 50). It is estimated that 16.5% of Veterans of these conflicts seek treatment from the Department of Veterans Affairs for co-occurring PTSD and pain (51). However, many more Veterans endorse PTSD symptoms that do not meet full criteria for a diagnosis of PTSD, as is consistent with the current findings. Specifically, the average score on the PCL-5 in this sample was 21.97, which is below the typical cut-off for probable PTSD (40). This suggests that interventions aimed at ameliorating even low levels of self-reported PTSD symptoms, particularly those above 15 on the PCL-5, may be an important area of emphasis for enhancing pain related outcomes for Veterans experiencing pain conditions.

Study analyses also contributed null findings. First, there were no significant gender differences in pain intensity or PTSD symptoms. This is consistent with previous work in Iraq and Afghanistan Veterans (52), but extends these findings to a larger age range. Second, results of exploratory analyses examining the interaction between age and PTSD symptoms on pain interference were not significant. Instead, the effect of age on pain interference was accounted for by PTSD symptoms. Although this may be surprising because pain intensity and pain interference are derived from the same measure (BPI), the result is consistent with the PCL-5 and BPI pain interference both measuring levels of burden.

Consistent with the biopsychosocial model of pain, successful reduction of PTSD symptoms may represent an effective intervention to decrease pain intensity. Currently, psychological interventions for pain tend to focus on Cognitive Behavioral Therapy or Acceptance and Commitment Therapy. These non-pharmacological approaches produce statistically significant, though small, reductions in pain intensity, but require further research due to methodological limitations, such as small sample size (53, 54). In addition to pain-focused psychotherapies, the results of the present study suggest that therapeutic approaches typically used for treatment of PTSD, such as Prolonged Exposure, Cognitive Processing Therapy for PTSD, or integrative treatments (55), may also be effective for Veterans with comorbid PTSD and pain.

There is a strong association between chronic pain and suicidality (10, 56–58) with highest risk of suicide among older white males (59). The current results suggest that treatment of PTSD symptoms, even significantly low symptoms, may be an important intervention for reducing suicidality, especially in older Veterans. Interventions aimed at reducing PTSD symptoms have been shown to be effective for reducing suicidal ideation (60), however this has not been evaluated in a pain population. Addressing pain through PTSD interventions could represent an effective intervention to reduce the risk of suicide among Veterans with comorbid pain and PTSD.

There are a number of research investigations that evaluated mechanisms underlying the relationship between PTSD symptoms and pain (61). Catastrophic thinking and avoidance are two cognitive-behavioral mechanisms that have gained significant attention as factors for maintaining both chronic pain and PTSD symptoms (61–63). However, these models have not included age. Though the effect size was relatively small, the current results suggest that age is an additional factor to consider in this relationship. It may be important to consider how avoidance and catastrophic thinking change across the lifespan, and how the subsequent changes to these cognitive-behavioral factors may affect outcomes.

The current results underscore the need for better understanding of mental health, particularly subthreshold PTSD symptoms, across the lifespan. Older adults are underrepresented in mental health research, therefore current policies may not adequately represent their interests. For example, PTSD is assumed to dissipate with age (17). However, this phenomenon could be due to changes in trauma reactions associated with aging rather than true recovery (64, 65). Further, older adults are, historically, less likely to receive treatment for PTSD (60). There is a growing recognition that mental health, and prior traumatic experiences specifically, remain a concern with advancing age (3). Additional research is necessary to better understand the mental health concerns of older adults. Future research should also inform training in geriatrics and best practices for working with Veterans at various points across their lifespan. Connecting older Veterans to treatment for PTSD symptoms and pain will remain critically important in the future, given the high prevalence of pain and mental health concerns among the Iraq and Afghanistan cohorts.

The results of this study demonstrate that the interaction between age and greater PTSD symptoms may exacerbate pain severity among Veterans. Whereas previous research has demonstrated a positive association between pain and age and a negative association between age and PTSD symptoms, addressing the interaction effects of these factors adds a new dimension to the current understanding of both pain and PTSD in aging Veterans. These preliminary findings suggest that treatment of PTSD symptoms may provide an additional avenue by which to address pain, especially among older cohorts.

This study contributes additional understanding of the relationship between pain and PTSD across the lifespan. When greater PTSD symptoms are present at older ages, Veterans report greater pain intensity. Providers should assess for trauma and PTSD symptoms among older Veterans reporting pain as a potential additional avenue of treatment.

VO’C, PhD, Research & Academic Affairs Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC, United States; Veterans Integrated Service Networks (VISN)-6 Mid-Atlantic Mental Illness, Research Education and Clinical Center (MIRECC), Durham, NC, United States; Department of Neurology, Wake Forest School of Medicine, Winston-Salem, NC, United States. JR, PhD, Research & Academic Affairs Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC; VISN-6 Mid-Atlantic MIRECC, Durham, NC, United States; Department of Neurobiology & Anatomy, Wake Forest School of Medicine, Winston-Salem, NC, United States. JN, PhD, VISN-6 Mid-Atlantic MIRECC, Durham, NC, United States; Durham Veterans Affairs Health Care System, Durham, NC, United States; Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC, United States. AM, PsyD, MA-MIRECC, Research & Academic Affairs Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC, United States; Department of Neurology, Wake Forest School of Medicine, Winston-Salem, NC, United States. KC, BFA, MA-MIRECC, Research & Academic Affairs Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC, United States. HM, PhD, Mental Health & Behavioral Sciences Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC, United States; Department of Neurology, Wake Forest School of Medicine, Winston-Salem, NC, United States. SM, PhD, MA-MIRECC, Research & Academic Affairs Service Line, W. G. (Bill) Hefner VA Healthcare System, Salisbury, NC, United States; Department of Physiology & Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, United States.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by Hefner VAHCS Institutional Review Board. The patients/participants provided their written informed consent to participate in this study.

VO’C: conceptualization, formal analysis, investigation, methodology, visualization, writing – original draft, writing – review and editing. JR: conceptualization, investigation, project administration, supervision, writing – review and editing. JN: conceptualization, writing – review and editing. AM and HM: investigation, writing – review and editing. KC: investigation, writing – review and editing. VA Mid-Atlantic MIRECC Workgroup: data curation, funding acquisition, project administration, resources. SM: conceptualization, data curation, formal analysis, investigation, methodology, supervision, visualization, writing – original draft, writing – review and editing. All authors contributed to the article and approved the submitted version.

The Mid-Atlantic MIRECC Workgroup contributors for this paper include: Jean C. Beckham, PhD, Patrick S. Calhoun, PhD, Eric Dedert, PhD, Eric B. Elbogen, PhD, John A. Fairbank, PhD, Robin A. Hurley, MD, Jason D. Kilts, PhD, Nathan A. Kimbrel, PhD, Angela Kirby, MS, Scott D. McDonald, PhD, Christine E. Marx, MD, MS, Scott D. Moore, MD, PhD, Rajendra A. Morey, MD, Robert D. Shura, PsyD, Cindy Swinkels, PhD, Larry A. Tupler, PhD, Elizabeth E. Van Voorhees, PhD, Tate F. Halverson, Ph.D., Pallavi Aurora, PhD., and Brandy S. Martinez, PhD.

This work was supported by the Salisbury VA Health Care System, VA Mid-Atlantic (VISN 6) Mental Illness Research, Education, and Clinical Center (MIRECC), and the Department of Veterans Affairs Office of Academic Affiliations Advanced Program in Mental Illness, Research, and Treatment.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

The views, opinions and/or findings contained in this article are those of the authors and should not be construed as an official Veterans Affairs position, policy, or decision, unless so designated by other official documentation.