Several studies have demonstrated that the primary active constituent of cannabis, delta-9-tetrahydrocannabinol, induces transient psychosis-like effects in healthy subjects similar to those observed in schizophrenia. However, the mechanisms underlying these effects are not clear. A new study shows that this active ingredient increases random neural activity, termed neural noise, in the brains of healthy human subjects. The findings suggest that increased neural noise may play a role in the psychosis-like effects of cannabis.