Andreasson, Allebeck, Engström and Rydberg follow 45,570 Swedish conscripts for 15 years and report in The Lancet that those who had used cannabis more than fifty times carry a sixfold risk of developing schizophrenia, the first statistical link between cannabis and the disorder.[1] The cohort covers nearly all Swedish men aged 18 to 20 at conscription, and an elevated risk remains after adjusting for other psychiatric history.[1][2]
Listed for context. No score change is recorded for Sweden here.
References
Checked. The date and the event were compared with a source that was read.