Some of the same genes associated with cannabis use are also associated with risk-taking personality types and psychiatric conditions like schizophrenia, according to a new large-scale genetic study.
The study, conducted by a team of scientists who are part of the International Cannabis Consortium, is the largest genome wide association study to date that looks at the use of cannabis.
The researchers found that people who are at a higher genetic risk for schizophrenia are also more likely to use cannabis. The study also identified 35 different genes associated with cannabis use with the strongest associations in the gene CADM2.
“CADM2 has already been associated with risky behaviour, personality and alcohol use,” said Jacqueline Vink of Radboud University, and the study’s lead author.
For this study, the researchers were able to look across more than a million genetic variants and found a genetic overlap between cannabis use and the use of tobacco and the use of alcohol. The researchers also saw an overlap between a higher likelihood for the use of cannabis and an increased risk for schizophrenia. 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, according to the researchers.
For this study, the researchers used data primarily from the UK Biobank, as well as association data from 23andMe customers who consented to participate in research. On top of that data the researchers used data from individuals in 16 other smaller study cohorts. In all the study included data from more than 180,000 people. In all the researchers found 35 genes associated with cannabis use, offering more insight into the genetic influences on personality types. The team of researchers was lead by Prof. Vink of Radboud University, and included contributions from researchers at QIMR Berghofer Medical Research Institute in Australia, as well as scientists at Virginia Commonwealth University, and 17 different research groups from Europe, North America and Australia.
The study showed that the genes increasing the risk of cannabis use partially increase the risk of schizophrenia as well. The researchers used an analysis technique called “Mendelian randomisation” to show a causal relationship between a genetic predisposition for schizophrenia and an increased risk of cannabis use. This may indicate 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 a genetic predisposition for cannabis could contribute to the risk of schizophrenia.
The team that worked on this study are already starting to explore which genes play a role in the frequency of cannabis use and the amount of cannabis used.
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