The cause and effect of mood disturbance in patients with ankylosing spondylitis

Abstract

Ankylosing spondylitis (AS) is a chronic inflammatory disorder, causing progressive pain and stiffness of the spine and peripheral joints. A systematic review of the literature revealed a high prevalence of possible depression (23-36%) and possible anxiety (45- 57%) in patients with AS. However, few existing studies have focussed on the relationships between mood and AS severity.

612 participants in a UK cohort of AS patients were included in the baseline postal survey. 470 patients responded to the six month follow-up survey thereafter. Several measures of disease status were collected [disease activity (Bath AS Disease Activity Index), pain (numerical rating scale) and physical function (Bath AS Functional Index)]. Mood was assessed by the Hospital Anxiety and Depression Scale. Improvements or deteriorations in mood and disease status were defined according to minimal clinically important differences in each measure.

298/612 (49%) patients reported depression/anxiety at baseline. Of whom, 166/298 (56%) demonstrated a co-existence of depression and anxiety; 27/298 (9%) had depression only and 105/298 (35%) had anxiety only. Although depression and anxiety were individually associated with increased disease activity, the strongest association was observed in patients with mixed depression and anxiety (OR 7.66, 95% CI 4.10-14.30). Similarly, there were significant associations of mixed depression and anxiety with poor function (OR 5.91, 95% CI 3.17-10.99) and increased pain (OR 4.76, 95% CI 2.56-8.86). In contrast to clinical expectations, there was no association between changes in mood or disease status over six months.

There is a high prevalence and frequent co-occurrence of depression and anxiety in patients with AS. Findings suggested that AS patients with mixed depression and anxiety had increased disease severity, however longer follow-up studies of more than six months are required to investigate these causal relationships. Anxiety and depression, as well as disease severity, should be considered when treating patients with AS.