British scientists claim they have found a link between marijuana consumption and the risk of developing psychotic manifestations later in life.

Smoking marijuana in small amounts increases the risk of developing psychosis by 40 percent, while heavy users of the drug can even become victims of schizophrenia.

The researchers analyzed 35 previous studies and found that smoking marijuana or cannabis raised the risk of hallucinating and being delusional later in life. The study, published in the latest issue of British journal The Lancet, also underlines that marijuana is the by far the most popular illegal drug in the US and the UK, and that preventing its consumption could decrease by 14% the number of psychoses in Britain.

“We now know that there is a long-term risk associated with the use of cannabis,” Merete Nordentoft, of the department of psychiatry at the Copenhagen University Hospital, said in an interview.

The researchers report an increased risk of up to 200 per cent for people who use cannabis most frequently.

According to the National Institutes of Health, the short-term effects of marijuana can include problems with memory and learning, distorted perception, difficulty in thinking and problem solving, loss of coordination and increased heart rate.

However, the authors say the risk to any individual of getting schizophrenia remains low overall, and that the conclusions of the study need to be taken with a grain of salt, because it’s a meta-analysis (a correlation of the conclusions of other studies on the same subject).

The studies that were examined included patients with disorders such as psychosis, schizophrenia, delusions and hallucinations, the researchers said. A link to depression or obsessive compulsive disorder couldn't be as clearly established, they said. The research was funded by the U.K.'s Department of Health.