Cannabis Makes You Mad

It is known that cannabis mashes up your brain, affecting brain nuclei even in unborn children, especially the cortex, the brain part involved in thinking, learning, attention and planning. Now a team has come with the strongest proof yet that using cannabis rises the risk of later developing psychotic illnesses like schizophrenia.

Cannabis smokers presented a 41% greater chance of experiencing such disorders than non-smokers. In case of heavy users, the likelihood to develop mental illnesses was even three times higher.

Cannabis is the most commonly used illegal drug worldwide, especially because users regard its effects as mild. In Britain, for example, around 40% of young adults have used cannabis at least once.

Previous studies have pointed to a connection between cannabis and symptoms similar to schizophrenia, like paranoia, hearing voices and visual illusions. "But the possible association has been an issue of tremendous debate and controversy for a long time. The science gets all mixed together with all the ideological views [about the drug]," said Rick Rawson, a professor at the University of California in Los Angeles, US.

Now, a British team has reviewed 35 researches on the long-term effects of cannabis use in Europe, the US and Australia for periods from one to 27 years. Those with pre-existing mental health issues were excluded from the analysis. Even so, there was a higher incidence of psychosis in cannabis users, pointing to the drug as a possible culprit. "Although you cannot be certain that the cannabis is causing this increase in risk, we think there is enough evidence to warn people," says co-author Glyn Lewis of the University of Bristol in the UK told New Scientist.

"If cannabis does cause psychosis, it could account for at least one in every 10 cases of diagnosed psychotic illness," the researchers say.

"There is a very good reason to be concerned. The evidence of a causal link in this latest study is very convincing but even better evidence may come once scientists understand how cannabis actually changes the brain", said Shaul Hestrin of Stanford University in California, US, who studies how cannabis-like substances affect neurons. "The big question is how to determine who's at risk." added Rawson.