Abstract
This review will focus on the incidence and prevalence of psoriasis, the risk factors for psoriasis and diseases that may be associated with psoriasis. Psoriasis is a heterogeneous disease and, for the purposes of this review, the focus will be plaque psoriasis. Prevalence studies indicate that psoriasis is a common disease and its frequency varies based on age, ethnicity and geography. Family history is the strongest risk factor for the development of psoriasis. Additionally, emerging evidence suggests that some potentially modifiable exposures such as smoking, alcohol, stress and obesity may increase a patient’s risk of developing psoriasis. The evolving literature suggests that psoriasis is associated with multiple other diseases including cancer, cardiovascular, autoimmune and psychiatric disease. Epidemiological studies of psoriasis contribute to measuring the public health burden of this disease and guide the care of patients with psoriasis through a better understanding of its natural history.