Risk of depression in women with psoriasis: a cohort study

Background Psoriasis is a common, chronic and inflammatory disease of the skin, which has been associated with depression in cross-sectional studies with limited adjustment for confounders. Objectives In this prospective cohort study, we investigated the risk of incident depression among individuals with psoriasis and psoriatic arthritis (PsA). Methods We included 50 750 US female nurses from the Nurses' Health Study who were free of depression at baseline in 2000. Those participants who had ever self-reported clinician-diagnosed depression or regular use of antidepressants, or had a Mental Health Inventory score of <= 52 were excluded. In 2008, we retrospectively asked participants if they had ever received a physician's diagnosis of psoriasis or PsA. We defined depression as self-report of clinician-diagnosed depression or regular use of antidepressant medication. Timedependent Cox proportional hazard models were used to estimate age and multivariate-adjusted relative risks (RRs) of clinical depression. Results After adjusting for covariates including body mass index, physical activity, smoking and the presence of major chronic conditions, the multivariate-adjusted RRs of clinical depression were 1.29 [95% confidence interval (CI) 1.10-1.52] for women with psoriasis and 1.52 (95% CI 1.06-2.19) for women with psoriasis and concomitant PsA, compared with women without psoriasis. Conclusions We found an increased risk of depression in US women with psoriasis compared with those without psoriasis. This risk was higher in those who reported concomitant PsA. Future studies are needed to confirm these findings in other populations and to identify pathophysiological mechanisms linking psoriasis to depression.