['To investigate whether psoriasis is affected by the use of serotonin reuptake inhibitors (SSRIs).', 'A population-based cohort study.', 'The general adult population with plaque psoriasis in Sweden between 1997 and 2006.', 'A total of 69 830 patients with plaque psoriasis were identified in the National Patient Register. Whether study subjects were exposed to SSRIs was identified through the Swedish Prescribed Drug Register. The SSRI-exposed subjects (n = 1282) had a prescription for SSRIs dispensed twice during 6 months at a Swedish pharmacy between 1 July 2006 and 1 April 2008, with a wash-out period of 1 year or longer. The reference subjects (n = 1282), who were not exposed to SSRIs, were matched for age, county of residence, sex, psoriasis severity and seasonal variation.', 'Change in psoriasis severity defined by switching between nonsystemic and systemic psoriasis treatments 6 months after exposure to SSRIs.', 'The risk of switching from nonsystemic to systemic psoriasis treatments was significantly decreased in the SSRI-exposed group (odds ratio 0.44, 95% confidence interval 0.28-0.68).'] Is use of serotonin reuptake inhibitors in patients with psoriasis associated with a decreased need for systemic psoriasis treatment : a population-based cohort study?