The principal psychoactive constituent of cannabis is Δ9-tetrahydrocannabinol (THC). THC administered intravenously is characterized by the appearance of psychopharmocological effects within 5 minutes, which continue for at least 90 minutes, providing an excellent experimental window.[12] In within-subjects tests with nonclinical volunteers, D'Souza, in particular, has shown that intravenous administration of THC causes schizophrenia-like symptoms, perceptual disturbances, anxiety, and impaired working memory (eg, Morrison et al[13] and D'Souza et al[14,15]). Similar but more pronounced results were found in patients with schizophrenia.[15]