I have my doubts that it's filled with myths - this is the Diagnostic and Statistical Manual of Mental Disorders. Admittedly, it's dated by about 9 years, but the next revision is supposed to be available sometime in 2012. This is, essentially, an encyclopedia entry on cannabis and it's use that doctors around the world rely on.
In all honesty, I remembered reading a section about consumption levels of thc that can induce a psychotic state, but I couldn't seem to find it in this entry.
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