Pot smoking linked to mental health problems.

Pot smoking linked to mental health problems. (Reuters)

Research points to cannabis-schizophrenia link

New research has revealed more evidence of a link between cannabis use and schizophrenia.

A national conference beginning in Melbourne today will examine international studies about the issue.

Professor David Castle from the University of Melbourne says there is already evidence showing some cannabis users can become psychotic.

He says the latest research shows if people with particular vulnerabilities smoke the drug, if can trigger more serious problems.

"The debate is whether if those people with those vulnerabilities do never use cannabis, whether they might never become psychotic or never develop schizophrenia and it's thought that probably from the literature now that maybe about one in 20 people with schizophrenia or about 5 per cent of them, might never become psychotic if they had never used cannabis," he said.

However, Professor Castle also believes cannabis is a valuable medicinal drug that is being restricted by its illicit nature.

He says it is a very effective drug in controlling nausea for cancer sufferers, a useful analgesic and an anti-bacterial agent.

"From the medical point of view, I believe that it's really important that the potential medicinal value of the drug is not lost through constraints put on it by legislators because there's a danger that research into the drug will be very difficult to do because it happens to be an illicit substance," he said.