Research Links Smoking "Potent" Marijuana With Psychosis: “Across the 11 study sites, those who use high potency on daily bases have over a 4 fold increase in the odds of having a psychotic disorder. This effect was greater in London and in Amsterdam, where high potency is more available.”

See the source article by following the link below:
Research Links Smoking "Potent" Marijuana With Psychosis: “Across the 11 study sites, those who use high potency on daily bases have over a 4 fold increase in the odds of having a psychotic disorder. This effect was greater in London and in Amsterdam, where high potency is more available.”