Do psychological factors predict outcome in both low-back pain and shoulder pain?

BACKGROUND AND OBJECTIVE Psychological factors are assumed to predict persistent or recurrent musculoskeletal pain. The influence of psychological factors in patients with low-back pain (LBP) or shoulder pain was explored to study whether there is similarity regarding the factors that predict persisting pain and disability. METHODS Patients presenting in primary care with a new episode of shoulder pain or non-specific (sub)acute low back pain (LBP) were enrolled in a prospective study. In both patient groups, pain catastrophising, distress, somatisation and fear-avoidance beliefs were measured at baseline. Primary outcome measures at 3 months were (1) persistent symptoms, and (2) <30% reduction in functional disability. Multivariate logistic regression analysis was used to study the associations between psychological factors and outcome. RESULTS A total of 587 patients with shoulder pain and 171 patients with LBP were enrolled in the study. In patients with shoulder pain, most associations of psychological factors with outcome were weak and not significant. Only in patients with longer symptom duration at baseline (>or=3 months) were higher scores on catastrophising significantly associated with persistent symptoms (p = 0.04). In patients with LBP, psychological factors were more strongly associated with poor outcome, although most associations were not significant. CONCLUSION Psychological factors, with the exception of fear-avoidance beliefs, are more strongly associated with persistent pain and disability in patients with LBP than in those with shoulder pain. This seems to indicate that in a primary care population the influence of psychological factors on outcome may vary across patients with different types of pain.