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A new scientific study has linked smoking cannabis with certain psychiatric conditions such as schizophrenia.

Researchers from Radboud University looked at data from more than 180,000 people as part of the study.

They uncovered that people with schizophrenia are also more likely to use cannabis.

The large-scale genetic study, published in Nature Neuroscience , was conducted by a team of scientists part of the International Cannabis Consortium.

(Image: Daniel Zgombic/Getty)

It's claimed to be the largest to date genetic study to look at the use of cannabis. It used data from the UK Biobank, association results from DNA testing kit 23andMe customers as well as data from individuals in 16 other smaller study cohorts.

The study identified 35 different genes associated with cannabis use with the strongest associations in a gene called CADM2.

“CADM2 has already been associated with risky behaviour, personality and alcohol use,” said professor Jacqueline Vink, the study’s lead author.

For this study, Vink and the researchers were able to look across more than a million genetic variants that together helped to explain approximately 11 percent of the differences in cannabis use between people.

(Image: Getty)

One of the biggest correlations that stood out was the genetic overlap between cannabis use and the risk of schizophrenia.

“That is not a big surprise, because previous studies have often shown that cannabis use and schizophrenia are associated with each other. However, we also studied whether this association is causal,” Vink explained.

“Our study showed that people with a vulnerability to develop schizophrenia are at increased risk of using cannabis.”

The researchers used an analysis technique called "Mendelian randomisation" to show a causal relationship between schizophrenia and an increased risk of cannabis use.

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This, the scientists said, indicated that people with schizophrenia use cannabis as a form of self-medication. However, the researchers cannot exclude a reverse cause-and-effect relationship, meaning that cannabis use could contribute to the risk of schizophrenia.

The study also found a genetic overlap between cannabis use and the use of tobacco and alcohol.

There was a similar overlap between cannabis use and personality types that were prone to more risky behaviour or were more extraverted.

"This means that genetic variants impacting cannabis use partially impact other psychological or psychiatric features as well," the researchers said.