Sweden never throws data away. They use their population as a epidemiological experiment. Including tracing people back to their conscription interviews… which happened when I was still in primary school.
This was a longitudinal study of 50,373 Swedish male military conscripts (ages 18–19) who were followed in the National Cause of Death Register up to around age 60. Cox proportional hazard modeling was used to assess risk of death in relation to baseline cannabis use and diagnosis of psychotic disorders.
Subjects with a baseline history of heavy cannabis use had a significantly higher risk of death (hazard ratio=1.4, 95% CI=1.1, 1.8) than those without such a history. The authors found an excess mortality among subjects with psychotic disorders, but the level did not differ between those with a history of cannabis use (ever users: hazard ratio=3.8, 95% CI=2.8, 5.0; heavy users: hazard ratio=3.8, 95% CI=2.6, 6.2) and those without such a history (hazard ratio=3.7, 95% CI=3.1, 44). No interaction was observed between cannabis use and diagnosis of psychotic disorders with regard to mortality.
The results suggest that individuals with an early history of heavy use of cannabis are at a higher risk of death than those with a history of no use of cannabis.
This is the survival curve. There may be a dose response curve.
Never is not ever having smoked cannabis: Some is between one and 50 times, heavy is over 50 times, Participants asked during conscription interviews Swedish army, 1969, 1970.
Cannabis use is associated with psychosis, but that does not explain this. I’d wonder what the cannabis was mixed with: some of the problems may relate to smoking.
It’s a heavy modifier of the CNS. In a clinical setting, you don’t enforce that type of effect unless absolutely necessary. Yet people use it without much care. There is always a cost to “checking out”. It wouldn’t surprise me if it’s years off your life.