Low Back Pain and Comorbid Posttraumatic Stress Disorder

The RMDQ is a self-reported outcome measuring the level of disability related to low back pain. The level of disability was measured on 23 statements covering six different domains: physical ability/activity, sleep/rest, psychosocial level of functioning, household management, eating, and pain frequency. Each statement was scored 1 if the patient felt that the statement was descriptive of their circumstances and scored 0 if not. The total RMDQ score ranges from 0 (no disability) to 23 (maximal disability). Scores were converted to percentages with 24 corresponding to 100% disability.

The Harvard Trauma Questionnaire consists of 17 items with a 4-point Likert scale (1 = not at all to 4 = very often). The 17 items relate to PTSD's core clusters within the Diagnostic and Statistical Manual of Mental Disorders (APA, 1994), 4th Edition (DSM-IV): avoidance (7 items), re-experiencing (5 items), and hyperarousal (5 items). An item was deemed to be positively endorsed if scores were ≥ 3. The Harvard Trauma Questionnaire follows the diagnostic criteria for the PTSD diagnosis according to the DSM-IV. The scale thus makes it possible to measure both the severity of symptoms and to estimate the prevalence of possible PTSD. Following the DSM-IV, a possible PTSD diagnosis was proposed if participants reported at least one re-experiencing symptom, three avoidance symptoms, and two hyperarousal symptoms.

Pain intensity was measured as the average score of three 11-point Likert scales measuring peak pain intensity, average pain intensity over the past 2 weeks as well as current pain intensity (Manniche, Asmussen, Lauritsen, Vinterberg, et Kreiner, 1994). Each scale measured pain intensity on a 0-10 numerical rating scale (NRS: Jensen, Karoly, & Braver, 1986) with 0 defined as no pain and 10 as the worst imaginable pain.

The Pain Catastrophizing Scale (Sullivan, Bishop, & Pivik, 1995) was used to measure catastrophic thinking related to pain. Its instructions ask participants to reflect on past painful experiences, and to indicate the degree to which they experienced each of 13 thoughts or feelings when experiencing pain, on a 5-point Likert scale with (0 = not at all, 4 = all the time). A scale sum score was calculated from all items, with a high score indicating a high level of pain catastrophizing.

Fear of re-injury due to movement was measured with the Tampa Scale for Kinesiophobia (TSK: Kori, Miller, & Todd, 1990). TSK is a 17-item scale assessing fear of movement on a 4-point Likert scale ranging from 17 to 68 with higher scores indicating higher levels of kinesiophobia. The scale is commonly used in diverse chronic pain samples and has good construct and predictive validity (Vlaeyen, Kole-Snijders, Boeren, & van Eek, 1995).

The scale consists of 14 items, seven relating to anxiety (HADS-A) and seven to depression (HADSD) with responses ranging from 0 (no symptoms) to 3 (maximum impairment). In the present study, we used a subscale cut-off of 8 in order to include all possible cases of anxiety or depression, as suggested by Zigmond and Snaith (1983).