Accumulating evidence suggests a role of oxidative stress in the pathophysiology of schizophrenia. The potent antioxidant sulforaphane (SFN) is an organosulfur compound derived from a glucosinolate precursor found in cruciferous vegetables such as broccoli, Brussels sprouts and cabbage. The protection afforded by SFN is thought to be mediated via activation of the NF-E2-related factor-2 (Nrf2) pathway and subsequent up-regulation of phase II detoxification enzymes and antioxidant proteins, through an enhancer sequence referred to as the electrophilic responsive element or antioxidant responsive element. Recently, we reported that SFN could attenuate behavioral abnormalities in mice after the NMDA receptor antagonist phencyclidine. Considering the potent antioxidant effects of SFN, we have a hypothesis that SFN would be a potential therapeutic drug for schizophrenia. The purpose of this study is to determine whether SFN-rich broccoli sprout extract have beneficial effects in patients with schizophrenia.