The study, published in 2012 in the journal Rheumatology, is the first large, double-blind, placebo-controlled
study of methotrexate for psoriatic arthritis. This
study design means half the subjects received methotrexate and half received placebo – and neither the study subjects nor the researchers knew who was getting which medication. This kind of study design is widely considered “the gold standard” because it eliminates bias.