Caveats, after all, are our specialty.
Previous studies had found a link (not necessarily a cause or effect) between cannabis use and psychosis. So researchers in Queensland, Australia, decided to investigate further and have now established what they consider a fairly strong connection between the length of marijuana use and the likelihood of psychosis in young adults.
The researchers even checked out pot use and psychosis symptoms among siblings just to make sure they haven't been missing some genetic or environmental factor. They don't seem to have been.
So pot use may well play some kind of role in what the researchers term "psychosis-related outcomes."
But, the researchers write in their conclusion: “The nature of the relationship between psychosis and cannabis use is by no means simple."
As they point out: "Those individuals who were vulnerable to psychosis (i.e., those who had isolated psychotic symptoms) were more likely to commence cannabis use, which could then subsequently contribute to an increased risk of conversion to a nonaffective psychotic disorder. In addition, analyses that incorporated adjustments for depressive and anxiety-related disorders led to a reduction in the strength of the association between cannabis use and psychosis-related outcomes. This suggests that depression and/or anxiety disorders may mediate or moderate the pathways between cannabis use and psychosis-related outcomes. We plan to further explore these issues in more detail in future studies."
This is fascinating and provocative stuff, especially as it pertains to young adults' still-developing brains. But the key word from the first paragraph is "associated."
So as for these headlines? "Long-term cannabis use can double risk of psychosis," "Study finds cannabis use is 'crazy-making'," "Teen pot smokers at high risk of mental illness," "Marijuana smoking teens prone to schizophrenia"... Perhaps some panic-quelling is in order.
Here's the full study, published online Monday in the Archives of General Psychiatry.
For a different look at marijuana, here's a recent L.A. Times story: UC studies find promise in medical marijuana
(Not cures, just promise.)
-- Tami Dennis
Credit: Daniel Karmann / EPA