BACKGROUND CONTEXT: It has been proposed that depression plays an important role in the course of low back pain, however there is considerable uncertainty regarding its predictive value. PURPOSE: To investigate the effect of depression on the course of acute and sub-acute low back pain. STUDY DESIGN: Systematic review. METHODS: We searched the following database using optimized search strategies: AMED, CINAHL, EMBASE, Health and Society Database (H&S), LILACS, MEDLINE, PsycINFO, Scopus, Web of Science. We only included prospective studies that investigated a cohort of participants with acute or sub-acute nonspecific low back pain (pain of less than 12 weeks duration). The prognostic factor of interest was depression or symptoms of depression assessed at baseline. The outcome of interest included: pain intensity, chronicity (non-recovery from low back pain), disability, return to work, health related quality of life, and overall patient satisfaction. Two independent reviewers selected studies, extracted data and assessed methodological quality of included studies. FUNDING: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. The authors declare no conflicts of interest-associated biases. RESULTS: 17 articles reporting 13 cohort studies were included in this review. There was considerable variability between studies in terms of method of assessment of depression and low back pain, statistical methods, and follow up length, which precluded the quantitative synthesis of the results. Definition of outcomes varied across studies, but overall they could be divided into work-related outcome measures, followed by disability, pain, self-perceived recovery, and mixed outcomes. Eleven out of 17 articles (or 8 out of 13 cohorts) reported that symptoms of depression at baseline are related to worse low back pain outcomes (measured in various ways) at follow up and the effect sizes (odds ratio) ranged from 1.04 to 2.47. Only two studies that did not find a statistical significant association reported quantitative results: OR = 1.03, 95% CI 0.98-1.08 and OR = 1.02, 95% CI 0.99-1.06. All included studies, regardless of the statistical significance, showed an effect in the direction of harm. CONCLUSIONS: Although a definitive answer on the effect of depression on the course of low back pain is not available, the findings of this systematic review suggest that depression might have an adverse effect on the prognosis of low back pain. Future large studies enrolling an inception cohort and employing a standardized method for assessing depression and low back pain are needed.
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