UK experts have found that people who frequently use the drug are at more than double the risk of developing psychotic illnesses like schizophrenia as compared to those who have never used it. Published in medical journal The Lancet, the findings are based on an analysis of results from 35 pervious surveys.
The study suggests that having used cannabis even once increases a person’s risk of developing psychotic problems by 41 per cent, which is an indication that 14 per cent of all psychotic illness in Britain is caused by cannabis use.
"The message that has to be made clear is there are potentially quite serious risks from using cannabis. For psychotic outcomes there certainly is enough evidence to warn people of the risk," Nature magazine quoted study author Stanley Zammit of Cardiff University, as saying.
He claims that the new analysis is the "most thorough" to date. "This adds a certain robustness to the evidence," he adds.
During their analysis, the experts found that even after allowing for other factors, such as other substance use and intelligence, people who had taken cannabis were 41 per cent more likely to develop schizophrenia or other psychotic problems than those who had never used it. People who used cannabis most frequently were more than twice as likely to suffer problems.
"Those figures are frankly quite staggering. Because cannabis is our most widely used illegal drug, I think any increased risk we have to be greatly concerned with. One can't take any comfort in the fact they may be relatively small numbers," says Neil McKeganey, director of the University of Glasgow's Centre for Drug Misuse Research.