Psoriasis and new-onset depression: A Danish nationwide cohort study

Abstract

Psoriasis is associated with an increased risk of depression, but results are inconsistent. This study examined the risk of new-onset depression in patients with psoriasis in a nationwide Danish cohort including some 5 million people in the period 2001–2011. A total of 35,001 patients with mild psoriasis and 7,510 with severe psoriasis were identified. Incidence rates per 1,000 person-years and incidence rate ratios (IRRs) were calculated. Incidence rates for depression were 20.0 (95% confidence interval 19.9–20.0), 23.9 (23.1–24.7) and 31.6 (29.5–33.8) for the reference population, mild, and severe psoriasis, respectively. Adjusted for age, sex, and inclusion year, IRRs were 1.08 (1.04–1.12) in mild and 1.36 (1.27–1.46) in severe psoriasis. After adjustment for comorbidity, the IRR was significant in only patients < 50 years with severe psoriasis (IRR 1.23 (1.03–1.46)). In conclusion, the risk of new-onset depression in psoriasis is mediated primarily by comorbidities, except in younger individuals with severe psoriasis, in whom psoriasis itself may be a risk factor.