Varma and Sharma (3) found an increased prevalence of cannabis use disorder in the first-degree relatives of schizophrenic probands. Working from the other direction, McGuire et al (4) found that within a sample of patients admitted with acute psychosis, the morbid risk of schizophrenia was increased for the relatives of probands who had tested positive for cannabis on urinary screening. These findings are consistent with the notion of a common genetic risk factor for cannabis abuse and schizophrenia. [...]
Most anti-psychotic medications work by suppressing dopamine. Drugs (like marijuana) that increase dopamine, might well be called pro-psychotic, in that they have the opposite effect of the anti-psychotics, on dopamine levels.
So people who are borderline, are pushed over the border by the increase in dopamine from marijuana or THC.
Reefer madness may not be for everyone, but it is for some.
A plausible theory - but I'm aware of no evidence that isn't equally well explained by the alternative theories above. And I'm not aware that there is yet any epidemiological evidence demonstrating the expected increase in incidence of schizophrenia within populations exposed to high levels of cannabis.
“we lack the crucial epidemiological evidence”
Lack of evidence, is not evidence. Such populations (exposed to high levels of cannabis) are markedly different in many respects. Accurate diagnosis and record keeping of psychotic events are very likely to be different across such cultures and sub-cultures. Hallucinations might be viewed as a feature, rather than a bug, to people seeking them, or in shamanic cultures -therefor not diligently reported to the authorities. Violent or destructive behavior from psychotic breaks might be recorded and treated as simple crime.
An epidemiological study is a very academic and abstract method of looking for effects, full of complex confounding factors, especially when direct biological models are easily available (although possible ethically riskier or more difficult for a non-medical academic, better suited to just library research).
Dopamine modulation can very reliably be shown to produce psychotic episodes in vulnerable individuals - just get a borderline psychotic and give them a hundred doses of THC in an extract oil - predictable and repeatable results - they will be tripping.
Give a less susceptible individual a thousand or 10,000 doses. They will also hallucinate profoundly. Seeing and hearing things that are not there is the very definition of psychosis. They would not be diagnosed as psychotics for epidemiological record keeping however, because the condition was induced, and not innate. They would pass a psychological evaluation easily, after the drugs wear off.
to;Dr == “Dave’s not here.”
Are “Varma and Sharma” just pen names for Cheech and Chong...?