The primary active constituent of cannabis, delta-9-tetrahydrocannabinol, increases the neural noise or the random neural activity in the brain of healthy users. The results suggest that neural noise play a role in inducing transient psychosis-like effects of cannabis in healthy subjects similar to those observed in schizophrenia.

Senior author Deepak Cyril D'Souza, a professor of psychiatry at Yale School of Medicine, said in a press release that delta-9-tetrahydrocannabinol (∆9-THC) produces these effects even if the doses given were roughly the equivalent of a half or a single joint. The researchers note that mechanisms underlying these effects are still unknown.

“The dose-dependent and strong positive relationship between these two findings suggest that the psychosis-like effects of cannabis may be related to neural noise which disrupts the brain's normal information processing,” added first author Jose Cortes-Briones, a postdoctoral associate in Psychiatry at Yale School of Medicine.

The researchers studied 24 participants for three days. The team administered two doses of ∆9-THC intravenously or placebo in these participants and then studied the drug’s effects on their electrical brain activity.

"This interesting study suggests a commonality between the effects on the brain of the major active ingredient in marijuana and symptoms of schizophrenia," stated John Krystal, editor of Biological Psychiatry. "The impairment of cortical function by ∆9-THC could underlie some of the cognitive effects of marijuana. Not only does this finding aid our understanding of the processes underlying psychosis, it underscores an important concern in the debate surrounding medical and legalised access to marijuana."

The researchers admit that more research must be done about this. Additionally, more information about the link between neural noise and psychosis could help researchers and healthcare professionals understand the biology of some of the symptoms associated with schizophrenia, providing the way to better treatment and management of the disease.