[otakucode]

Every study done, and likely to ever be done given ethical standards, attempting to link marijuana usage to mental illness shares the same fundamental problem which makes their results meaningless: It cannot account for self-selection. There is no way to know that those who would later be diagnosed with schizophrenia were not self medicating with marijuana, leading to the causation actually being backwards. And in that case there is also no way to know what effect preventing that self medication might have had, and whether it would be positive or negative.

Short of a plausible neurochemical explanation of how it would happen, phenomenological studies like those have to be discarded. They simply don't have the ability to illuminate anything, they can only feed intuitive guesses which is always dangerous in issues of health.

[mywittyname]

This same argument could be applied to many long-term medical studies: Maybe people with a pre-disposition to heart disease also hate exercising, so the link between heart disease is and lack of exercise is backwards. Yeah, that doesn't work.

Ignoring the link between mental illness and marijuana use is ridiculous. A medical study doesn't need 100% confidence to be true. If we held all of medical science to that bar, we'd never make progress.

Plus, we have a colloquialism for a person whose mind appears to have suffered damage from excessive marijuana usage: a burnout. It's something that even recreational users observe. And where there's smoke...

[bsder]

> Ignoring the link between mental illness and marijuana use is ridiculous.

Your statement presupposes the conclusion. You need to consider two different questions:

1) Do we have correlation between marijuana usage and mental illness above and beyond the line for something as common as alcohol or cigarettes?

2) Do we have have causation between marijuana and mental illness?

Most studies barely reach an "inconclusive, needs more study" on 1). 2) isn't even in scope yet.

> Plus, we have a colloquialism for a person whose mind appears to have suffered damage from excessive marijuana usage: a burnout.

We also have a word for someone with the same issue on a different drug--alcoholic.

I'm pretty sure we have far more conclusive evidence of the mental damage that alcohol does than the damage that marijuana does.

[mywittyname]

Alcohol is a red herring and serves no purpose in this discussion. The public has been made aware of the dangers of alcohol consumption.

> The relationship between cannabis and schizophrenia fulfills many but not all of the standard criteria for causality, including temporality, biological gradient, biological plausibility, experimental evidence, consistency, and coherence. At the present time, the evidence indicates that cannabis may be a component cause in the emergence of psychosis, and this warrants serious consideration from the point of view of public health policy. [0]

That's pretty solid, and far from "inconclusive." Animal testing have already confirmed that mice with certain genetic markers will develop schizophrenia if exposed to THC. [1]

[0] https://www.ncbi.nlm.nih.gov/pubmed/24904437

[1] https://www.medicalnewstoday.com/articles/317170.php

[mike10010100]

> That's pretty solid, and far from "inconclusive."

It's literally what he said: "inconclusive, needs more study".