Objectives: The purpose of this study was to examine the relative contribution of medical variables, illness perceptions, coping and alexithymia to the variance in stress, distress and disability in patients with psoriasis.
Design: Cross-sectional study.
Method: A group of 225 patients with psoriasis completed the Hospital Anxiety and Depression Scale (HADS), The Penn State Worry Questionnaire (PSWQ), the COPE, the Illness Perception Questionnaire (IPQ), Toronto Alexithymia Scale (TAS-20), and two measures specific to psoriasis, the Psoriasis Disability Index (PDI), and the Psoriasis Life Stress Inventory (PLSI). The severity of patients' psoriasis was clinically assessed by dermatologists on the Psoriasis Area and Severity Index (PASI).
Results: In general, demographic variables, clinical history and extent of disease were consistently the least useful variables in terms of explaining variance in stress, distress or disability. Their utility was limited to accounting for small but significant variations in disability, but even in this case, they accounted for just over half as much variance as illness perceptions. Illness perceptions were uniformly the most important variables in terms of the variance accounted for in outcome. Coping varied widely in its explanatory power; its effects were negligible in both disability (PDI) and everyday stress (PLSI), and it was moderately important in accounting for additional variance in depression and anxiety. However, coping was important in explaining the variance in pathological worrying. Alexithymia accounted for significant additional variance chiefly for anxiety and to a lesser extent for depression, worrying and psoriasis-related life stress.
Conclusion: The observed importance of cognitive factors in stress, distress and disability invite us to consider the utility of multivariate models of outcome in psoriasis.