The relationship between depressive symptoms, illness perceptions and quality of life in ankylosing spondylitis in comparison to rheumatoid arthritis

Anxiety and depressive symptoms as well as cognitive variables are important in determining outcome in rheumatic diseases. We aimed to compare psychological distress symptoms and illness perceptions in ankylosing spondylitis (AS) and rheumatoid arthritis (RA) and to test whether their associations with health-related quality of life (HRQoL) were similar in these rheumatologic disorders. In 55 AS and 199 RA patients, we administered the Patient Health Questionnaire (PHQ-9), the Symptom Check-List and the Brief-Illness Perception Questionnaire to assess psychological variables and the World Health Organization Quality of Life Instrument, Short Form to assess HRQoL. We used hierarchical regression analyses to determine the associations between psychological variables and HRQoL after adjusting for demographic variables and disease parameters. The prevalence of clinically significant depressive symptoms (PHQ-9 ≥ 10) was 14.8 % in AS and 25.1 % in RA patients, but adjustment for demographics rendered these differences in depressive symptoms' severity non-significant. Psychological distress levels and HRQoL were similar in both disorders. Illness concern (b = -0.37) was the only significant independent correlate of physical HRQoL in AS. In RA, depression (b = -0.25), illness concern (b = -0.14) and worries about the consequences of the disease (b = -0.31) were the independent correlates of physical HRQoL. These findings suggest that cognitive variables are important correlates of HRQoL in AS, whereas in RA depressive symptoms and illness perceptions equally contribute to HRQoL. Our data encourage the design of psychotherapeutic trials targeting disease-related cognitions in AS in an attempt to improve patient's physical HRQoL.