Objective: To describe the prevalence and costs of anxiety and depression among moderate-to-severe psoriasis (PsO) patients in a commercially-insured US population.Methods: The IBM MarketScan Commercial database was used to select adults with moderate-to-severe PsO (≥1 PsO diagnosis and ≥1 systemic or biologic medication) within each calendar year from 2014 to 2016. Adults with no diagnosis of PsO or similar disorders were randomly selected (2014-2016) and matched 1:1 to PsO patients to compare the prevalence of anxiety and depression each year. Moderate-to-severe PsO patients identified in 2014 with continuous enrollment through 2015 were stratified into those with treated anxiety and/or depression (≥1 anxiety or depression diagnosis plus any anxiolytics, antidepressants, or antipsychotics within 30 days) vs those without anxiety/depression, and then matched 1:1 to determine the incremental burden of treated anxiety/depression among PsO patients. All-cause and PsO-related healthcare costs were compared between the matched cohorts using generalized linear models.Results: In total, 69,644 matched PsO and non-PsO patients were identified in 2014, 61,478 in 2015, and 66,880 in 2016. The prevalence of anxiety/depression among PsO patients increased more than for matched controls, from 18.2% vs 12.2% in 2014 (p < 0.01) to 19.6% vs 13.1% in 2016 (p < 0.01). Prevalence of treated anxiety/depression followed the same trend, with increases from 14.5% vs 8.9% in 2014 (p < 0.01) to 15.9% vs 9.9% in 2016 (p < 0.01). For patients with moderate-to-severe PsO, unadjusted incremental all-cause healthcare costs associated with treated anxiety/depression were $8,077 (p < 0.01); 91% was due to utilization of medical services such as hospitalizations, ER visits, office visits, and other outpatient services (all p < 0.01).Conclusions: The prevalence of psychiatric disorders is higher among PsO patients than the general population, and the incremental burden of treated anxiety/depression is substantial. Further research is needed, but PsO treatments that improve psychiatric symptoms such as anxiety/depression may benefit patients and reduce their economic burden.