Smoking cannabis can induce psychosis-like effects, similar to the symptoms people diagnosed with schizophrenia endure, scientists have said.

While past research as come this this conclusion in the past, the mechanisms underlying these effects are less clear.

Now, a team of scientists at Yale School of Medicine have found the active ingredient in marijuana, delta-9-tetrahydrocannabinol (delta-9-THC) increases random neural activity, known as neural noise, in the brains of healthy drug-users.

Yale scientists found at doses roughly equivalent to half or a single joint, the active ingredient in cannabis, delta-9-THC, produces psychosis-like effects and increased neural activity in the brains of healthy people

Their findings suggest increased neural noise may play a role in the psychosis-like effects of cannabis.

Dr Deepak D'Souza, a professor of psychiatry at Yale, said: 'At doses roughly equivalent to half or a single joint, delta-9-THC produced psychosis-like effects and increased neural noise in humans.'

First author of the study, Dr Jose Cortes-Briones, a postdoctoral associate in psychiatry at Yale, added: '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.'

Researchers studied the effects of delta-9-THC on electrical brain activity in 24 human subjects, who took part in a three-day study.

During the experiments, they received two doses of intravenous delta-9-THC or a placebo in a double-blind, randomised, cross-over and counterbalanced design.

If confirmed, the link between neural noise and psychosis could shed light on the biology of some of the symptoms associated with schizophrenia.

Dr John Krystal, editor of Biological Psychiatry, the journal in which the study is published, said the research marks an important part of the debate over whether cannabis should be legalised.

He said: 'This interesting study suggests a commonality between the effects on the brain of the major active ingredient in marijuana and symptoms of schizophrenia.

'The impairment of cortical function by delta-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.'