BACKGROUND: Psoriasis negatively impacts sleep, but the factors that cause this sleep disturbance are not well characterized. PURPOSE: To assess sleep quality in subjects with psoriasis. METHODS: 35 outpatients diagnosed with chronic plaque psoriasis affecting at least 10 percent BSA and 44 controls completed the Pittsburgh Sleep Quality Index, Patient Health Questionnaire, Itch Severity Scale, Insomnia Severity Index, and Epworth Sleepiness Scale. For multiple testing, alpha was set at 0.008. RESULTS: Adjusting for age, BMI, and gender, patients with psoriasis had 4.3 times the odds to score in a higher insomnia category (OR 95% CI: 1.7, 11.2; p=0.01), a trend toward experiencing "poor sleep" (p=0.04), and no difference in odds to be "sleepy" (p=0.83). Patients with psoriasis had greater itch than those without psoriasis (mean ISS 8.5 vs. 2.0; p<0.0001). When adjusting for age, BMI, gender, and depression, those with psoriasis were not more likely to experience poor sleep quality (p=0.25), nor to score in a higher insomnia category (p=0.20) or be more "sleepy" (p=0.53). CONCLUSIONS: Patients with psoriasis suffer from sleep disturbances and pruritus more than those without psoriasis. Although sleep disturbances are more prevalent, this may be secondary to depression rather than related to a direct effect of psoriasis.