Cannabidiol (CBD), a non-tetrahydrocannabinol (THC) cannabinoid in Cannabis sativa, has previously been shown to attenuate tetrahydrocannabinol-induced psychotic symptoms and cognitive decline in healthy volunteers and may reduce psychotic symptoms in small studies of patients with schizophrenia and Parkinson disease. However, although CBD seems benign, its clinical effectiveness appears to be minimal and limited to a few patients, at least in this study.