The exact nature of the relationship between schizophrenia and cannabis still isn't clear to scientists, but a new study offers additional clues. Researchers studied genetic data on 2,082 people, about half of whom had used cannabis, Reuters reports; they focused on the number of schizophrenia-linked genes in the subjects. The experts found that those with a predisposition to the illness were more likely to use cannabis—and to use more of it—than were those without schizophrenia-linked genes, regardless of mental health history.
In other words, says a researcher, the study suggests "a pre-disposition to schizophrenia also increases your likelihood of cannabis use." The Verge explains the complexities of the possible relationship between schizophrenia and marijuana: In the 1960s, for instance, scientists thought that smoking marijuana could cause psychosis in most people; these days, researchers believe using the drug may spur schizophrenia in those who are predisposed to it. The new study effectively turns the idea around, suggesting that those who are predisposed to the illness may also be predisposed to using marijuana. But that doesn't mean weed use doesn't increase schizophrenia risk, an outside expert notes: "Both (theories) may be true."