This study will capitalize on conditioned immunosuppressive responses to reduce the cumulative amount of corticosteroid medication used in the treatment of psoriasis. We will continue to treat patients with steroid, but will shift experimental patients from their current schedule of continuous reinforcement (active drug whenever medication is applied) to a partial schedule of reinforcement (active drug a percentage of the time and placebo alone at other times). To equate amount of medication, we will treat another group of patients with a reduced dose of steroid in a standard treatment regimen (continuous schedule of reinforcement).