For more information regarding Bristol-Myers Squibb Clinical Trial participation, please visit www.BMSStudyConnect.com  Inclusion Criteria:  Diagnosis of moderate-to-severe Psoriasis (PsO) by physician (phase 1) or self-reported (phase 2) Currently taking systemic psoriasis treatment Japanese resident aged 20 years and older  Exclusion Criteria:  Unable or unwilling to provide informed consent Diagnosis of guttate, inverse, pustular, erythrodermic, or drug-induced psoriasis