Smoking powerful dagga each day can increase the chances of developing psychosis almost five times, according to the largest ever study of the effect of cannabis on indicators of psychotic disorders.
Research supplements previous studies that have shown links between marijuana and mental health problems, but they still do not define marijuana as a cause.
Psychotic disorders – in which people lose touch with reality – are usually caused by factors, including genetics and the environment. Experts say, however, that the results of new research have an impact on the legalization of dagga legalization, warning that they should consider the potential impact on their mental health services.
"If we think there is something special about (high power), cannabis, and then getting them difficult, they can be a useful means of harm reduction," said Suzanne Gage from the University of Liverpool, who was not related to the new study.
Researchers from King s College London and other countries have analyzed data from more than a dozen locations in Europe and Brazil in 2010-2015. About 900 people were compared, who were diagnosed with the first episode of the disorder in the mental health clinic, including delusions and hallucinations. from over 1,200 healthy patients.
After investigating patients on the use of dagga and other drugs, researchers found that the daily use of marijuana was more common among patients with the first episode of psychosis compared to a healthy control group.
Researchers estimated that people who smoked marijuana every day were three times more likely to be diagnosed with psychosis than people who never used the drug. For those who used powerful cannabis every day, the risk increased almost five times.
The article was published online last week by the magazine Lancet. It has been paid for by funders, including the British Council for Medical Research, the Sao Paulo Research Foundation and the Wellcome Trust.
"If you decide to have high-powered marijuana, you should remember: Psychosis is a potential risk," said Dr. Marta Di Forti from King s College London and the lead author of the study. She said that it is not known how often people can smoke less powerful marijuana without increasing the likelihood of psychosis, but the fact that less than weekly use does not seem to be a risk.
Di Forti and his colleagues estimated that in Amsterdam about half of the new cases of psychosis were associated with high-powered dagga smoking.
Gage noted that it is possible that people with psychosis or other risk factors in the family may be more susceptible to problems such as psychosis or schizophrenia if they use cannabis.
"This may be something that is outweighed by some people," she said. "Cannabis for them can be an additional risk factor, but they definitely do not have to be involved. If you use cannabis, it does not mean that you will definitely develop psychosis. "