A genetic study found evidence of a connection between cannabis use and schizophrenia but it is still unclear if the drug leads to the disorder or vice versa. The study relies partly on genetic data from 23andMe volunteers that might offer some answers to this evidence. It found that people genetically at risk for schizophrenia are also more likely to start smoking pot.

The study, published in Nature Neuroscience, is a continuation of previous efforts to point out the genetic variations that make people more likely to start using cannabis. Researchers from DNA test company 23andMe studied anonymous genetic data taken from previous or ongoing studies. According to authors, researchers looked at more than 180,000 people, which makes this the largest study of its kind.

In the study, the researchers found eight SNPs (a minute change in the building blocks that make up our DNA and RNA, also known as nucleotides) that were associated with lifetime cannabis use. Using different tests, they also found 35 genes in 16 different sections across the genome that were associated with cannabis use. Many of these genes were also linked to other habits, personality traits, and mental health conditions. “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,” reported Jacqueline Vink, a researcher at Radboud University in the Netherlands.

Researchers also found evidence that being genetically vulnerable to schizophrenia made people more likely to use pot, possibly as a way to cope with their conditions. This is very important because researchers still don’t really understand how cannabis and schizophrenia are tied to one another. Other research has established that pot use itself raises the risk of schizophrenia, especially if started at a young age by people already at risk of mental illness. The investigators next plan is to study if there are specific genes that can predict more frequent of heavier use of cannabis.