Erowid References Database
Fergusson DM, Horwood LJ, Ridder EM.
“Mirken refuted: reasons for believing that the association between cannabis use and risk of psychosis is probably causal”.
Addiction. 2005 May;100(5):715-6.
In his comment on our research, Mirken  suggests that our conclusions that ‘our findings add to the growing body of evidence that regular cannabis use may increase risks of psychosis’ can be explained by the fact that ‘the case for marijuana causing mental illness is based solely on marijuana smokers having the completely reasonable feelings that they have different beliefs from mainstream
society . . .’. These arguments succeed only by virtue of Mirken ignoring most of the body of evidence to which we refer. In particular, it has been well established by longitudinal studies that the heavy use of cannabis is associated with increased rates of both psychosis [2,3] and psychotic symptoms [4–8]. This consistent finding using different approaches to assessing psychosis and psychotic
symptoms makes it very difficult to claim that the link between cannabis and psychosis/psychotic symptoms simply reflects the fact that cannabis users have different beliefs from the rest of society.
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