Does chronic pain predict future psychological distress?

Cross-sectional studies have consistently shown a relationship between chronic widespread pain, the clinical hallmark of fibromyalgia, and psychological distress. These studies cannot distinguish the direction of any causal relationship. Recent population based studies have reported that such pain is predictive of future distress. However, chronic pain is often associated with physical and psychological co-morbid features which may confound this relationship. The aim of this study was to examine the hypothesis that chronic widespread pain increases the risk of future distress after adjusting for the effects of possible confounding factors. A population based survey of 1953 individuals identified subjects' psychological status and whether they satisfied criteria for chronic widespread pain. At baseline co-morbid features of chronic widespread pain, including reporting other somatic symptoms, abnormal illness behaviour, health anxiety, fatigue and low levels of self-care, were measured. All subjects were followed up after 12 months to determine levels of psychological distress. Subjects with chronic widespread pain at baseline were much more likely to be distressed at follow up (OR=4.0, 95% CI (2.5,6.3)). As levels of distress at follow up may simply reflect those at baseline the association was adjusted for baseline levels of distress. Chronic widespread pain was, however, still associated with future distress although the relationship was slightly attenuated (odds ratio, OR=3.0, 95% CI (1.8,5.1)). To examine our main hypothesis a final analysis was undertaken adjusting this association for those co-morbid features assessed at baseline. Following these adjustments chronic widespread pain was no longer significantly associated with future distress (OR=1.5, 95% CI (0.8,2.9)). Chronic widespread pain was associated with increased levels of psychological distress at follow up. However, a more rigorous analysis indicated that the association between baseline pain status with future distress was explained by concomitant features of chronic pain rather than pain per se. These findings indicate that it is those persons with chronic widespread pain in the presence of other physical and psychosocial factors who will become distressed.