The relationship between pain and depression in a trial using paroxetine in sufferers of chronic low back pain

Previous studies have shown a positive association between pain and depression, though evidence supporting a direct link between these two variables is less robust. Using a placebo-controlled trial, the authors examined the analgesic and antidepressant efficacy of paroxetine (20 mg) in chronic low back pain sufferers. The authors examined the associations among pain, depression, disability, and illness attitudes. Paroxetine showed no effects on pain or depression compared with placebo; however, subjects randomized to paroxetine were more likely to reduce concomitant analgesic medication. The cross-sectional association of depression and pain at baseline (r = 0.2, P = 0.02) was weaker than the association between depression and disability (r = 0.3, P = 0.004). Similarly, the association of change in depression scores with change in pain (r = 0.25, P = 0.016) was weaker than change between depression and disability (r = 0.49, P<0.0005). Whereas the relationship between pain and depression became nonsignificant when disability and illness attitudes were controlled, the relationship between depression and disability remained highly significant when pain and illness attitudes were controlled. These data are consistent with the association between pain and depression being wholly modulated by disability and illness attitudes, with no direct relationship between pain and depression.