Cannabis use can trigger psychotic illness in sufferers almost three years earlier than in those who do not use the drug, Australian research found.

Analysis of data on 22,000 patients with psychosis showed a link between the age at which sufferers developed symptoms and their cannabis usage, researchers from the University of New South Wales said Monday.

The study, comprising more than 8,000 patients who were cannabis users and more than 14,000 who did not use the drug, found that those who used cannabis developed psychosis, such as schizophrenia, around 2.7 years earlier than those who did not.

"The results of this study provide strong evidence that reducing cannabis use could delay or even prevent some cases of psychosis," said Dr. Matthew Large, who led the study. "Reducing the use of cannabis could be one of the few ways of altering the outcome of the illness because earlier onset of schizophrenia is associated with a worse prognosis and because other factors associated with age at onset, such as family history and sex, cannot be changed."

The study, which will be published in the journal Archives of General Psychiatry, concluded that "the results of this study confirm the need for a renewed public health warning about the potential for cannabis use to bring on psychotic illness."