Depression, somatization, and somatic dysfunction in patients with nonspecific chronic low back pain: results from the OSTEOPATHIC Trial.

CONTEXT Depression and somatization are often present in patients with chronic low back pain (LBP). OBJECTIVES To measure the presence of depression and somatization in patients with chronic LBP and to study the associations of depression and somatization with somatic dysfunction, LBP severity, back-specific functioning, and general health. DESIGN Cross-sectional study using baseline measures collected within a randomized controlled trial. SETTING University-based study in Dallas-Fort Worth, Texas. PATIENTS A total of 202 adult research participants with nonspecific chronic LBP. MAIN STUDY MEASURES Depression was self-reported and also measured with the Modified Zung Depression Index (MZDI). Somatization was measured with the Modified Somatic Perception Questionnaire (MSPQ). The MZDI and MSPQ scores were used to classify patients as "normal," "at risk," or "distressed" using the Distress and Risk Assessment Method. Somatic dysfunction was assessed using the Outpatient Osteopathic SOAP Note Form. A 100-mm visual analog scale (VAS), the Roland-Morris Disability Questionnaire (RMDQ), and the Medical Outcomes Study Short Form-36 Health Survey (SF-36) were used to measure LBP severity, back-specific functioning, and general health, respectively. RESULTS There were 53 patients (26%) and 44 patients (22%) who were classified as having depression on the basis of self-reports and the MZDI cut point, respectively. A total of 38 patients (19%) were classified as having somatization on the basis of the MSPQ cut point. There were significant correlations among self-reported depression and the MZDI and MSPQ scores (P<.001 for each pairwise correlation). Similarly, the MZDI and MSPQ scores were both correlated with LBP severity and back-specific disability, and they were inversely correlated with general health (P<.001 for each pairwise correlation). Depression and the number of key osteopathic lesions were also each correlated with back-specific disability and inversely correlated with general health (P<.001 for each pairwise correlation). The MZDI (P=.006) and MSPQ (P=.004) scores were also correlated with the number of key osteopathic lesions. CONCLUSIONS The associations among depression, somatization, and LBP in this study are consistent with the findings of previous studies. These associations, coupled with the findings that MZDI and MSPQ scores are correlated with somatic dysfunction, may have important implications for the use of osteopathic manual treatment in patients with chronic LBP.