**1. Introduction**

Comorbid post-traumatic stress disorder (PTSD) and chronic pain are common among Veterans [1–3]. Chronic pain can amplify the symptoms of PTSD and complicate treatment, resulting in a greater use of healthcare services, which may be caused by poorer response to pain treatment [4–7]. Veterans with comorbid chronic pain and PTSD report having a poorer quality of life and have worse pain and psychological outcomes than those without concurrent disorders [8–10]. Specifically, Veterans with both PTSD and chronic pain have increased pain intensity or severity, can have pain-related disability, pain catastrophizing, and an increase in depressive and anxiety symptom severity [11–16]. Chronic pain can also result in greater psychiatric symptom instability among Veterans with PTSD [9,10]. As such,

**Citation:** Pratt, A.A.; Hadlandsmyth, K.; Mengeling, M.A.; Thomas, E.B.K.; Miell, K.; Norman, S.B.; Lund, B.C. The Impact of Comorbid Chronic Pain on Pharmacotherapy for Veterans with Post-Traumatic Stress Disorder. *J. Clin. Med.* **2023**, *12*, 4763. https://doi.org/10.3390/jcm12144763

Academic Editors: Robert Barkin and Massimiliano Valeriani

Received: 18 April 2023 Revised: 22 June 2023 Accepted: 13 July 2023 Published: 19 July 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

comorbid chronic pain and PTSD may result in an accumulation of multiple medications to treat these conditions [17]. Specifically, severe PTSD symptoms, magnified by chronic pain, may require more frequent psychotropic medication changes across time. However, it has not been clearly demonstrated whether those with comorbid chronic pain and PTSD receive more CNS medications or have more frequent psychotropic medication changes than those with PTSD but without chronic pain.

The siloed management for PTSD and chronic pain can result in the prescription of multiple concurrent central nervous system (CNS)-active medications [17,18]. Polytherapy with CNS-active medications can increase the risk of overdose mortality, suicide-related behaviors, and unintentional death [19]. Other effects of polytherapy can include the following: increased healthcare costs, adverse drug events, drug interactions, medication non-adherence, individual functional decline, cognitive impairment, falls, urinary incontinence, and change in nutritional status [20–22]. Polytherapy among Veterans with comorbid PTSD and chronic pain may result from an additive effect of multiple conditions, or it may be impacted by increased difficulties in managing psychiatric symptoms in the presence of comorbid chronic pain.

The current study aims to examine the impact of comorbid chronic pain on Veterans with PTSD via psychopharmacological prescription patterns. Specifically, this study aims to (1) determine the impact of chronic pain on a number of psychiatric medication changes across time (as an indicator of treatment instability) among Veterans with PTSD, and (2) determine the impact of comorbid chronic pain on the risk of multiple concurrent CNSactive medication prescriptions among Veterans with PTSD. We hypothesized that Veterans with chronic pain would have more psychiatric medication changes across time and have a higher number of concurrent CNS-active medications.
