> Why is it so hard for many HN readers to consider that cannabis might cause schizophrenia? There are tons of studies demonstrating a correlation, so it's not impossible that there is a causation too.

If you went to school in the United States in the 1980's or 90's, you were lectured consistently and repeatedly by teachers, parents, medical professionals and police offices about the horrendous dangers of marijuana. The basic storyline was something like: if you took a puff of marijuana you would quickly degenerate into a slobbering drug addict and end up fellating some crack dealer for a $5 rock, after which you'd contract AIDS and die an agonizing death. So over the years, the folks doing the anti-cannabis messaging lost a lot of credibility, which is why folks are rightly skeptical of new anti-cannabis claims.

Note: There's a little hyperbole in here, but only a little. U.S. drug education was pretty bonkers in the 80's and 90's.

1. Many years of anti-cannabis propaganda and the war on drugs, despite never really studying the effects of cannabis, makes people skeptical of research like this.

2. This article in no way states that cannabis usage causes schizophrenia. It says there is a correlation, and furthermore the fact that both low and high usage having the same effects. That actually harms the case that it DOES, since you would expect the odds of it causing issues would increase with amount ingested.

> That actually harms the case that it DOES, since you would expect the odds of it causing issues would increase with amount ingested.

Not necessarily? The correlation is observed, and there may be causation, in one, or both, directions, that is all we can conclude from the study. The causality doesn't have to be linear with the amount ingested, few things are linear in biology. For example, one could imagine that a certain amount blocks the development of a particular region of the brain. Ingesting more does not necessarily blocks it "more".

There is no evidence that this happens, but it is worth exploring, because schizophrenia is a hell of a condition, and is still largely misunderstood.

This sounds like anti-vaxx talking point, government messaging and scientific research on the subject are two different things.

I'm not sure how this relates to anti-vaxx, which I am extremely anti-anti vaxx.

I'm saying we cannot interpret this research study the way people want to. Correlation != causation, and the results on this seem murky in general, as outlined how amount consumed does not affect likelihood of symptoms.

Comparing modern Covid research to this is... dishonest. We have a massive amount of data to parse and analyze with vaccine effectiveness etc.

Meanwhile, this is a single meta-study that doesn't make any strong claims.

> Why is it so hard for many HN readers to consider that cannabis might cause schizophrenia?

Currently, approximately 129M US adults have used cannabis and there are 3.2M schizophrenics in US. 16% of schizophrenics use cannabis, while 27% have a history of using cannabis. This makes any correlation, if there is one, extremely difficult to see, because currently, at best, only 864K schizophrenics of 3.2M have ever used cannabis. This means, if there is actually a causation, then using cannabis entails a risk of 1 in 149.3 of causing schizophrenia, which seems high until you consider schizophrenia affects 1 in 300 people worldwide. So it is possible that using cannabis doubles risk of schizophrenia, but we wouldn't say it caused it. 100% of schizophrenics drink water... why isn't drinking water researched as a cause of schizophrenia?

These arguments are shoddy and you know that. If it was so difficult to demonstrate a correlation then so many studies wouldn't have been able to do just that.

Not an argument, just answering the question.

Also,

> If it was so difficult to demonstrate a correlation then so many studies wouldn't have been able to do just that.

employs a fallacy, assuming the conclusion aka begging the question. But that's ok, because I'm really not arguing any position.

DARE and similar anti-drug propaganda lied through their teeth about the real consequences of using drugs. The war on drugs has been lost completely, but they continue to persecute low-level drug offenders when the distribution channels remain completely unaffected. The government (and by extension government-funded research) has proven itself unable to be trusted in this area.

Thank you, I feel much the same. It feels a bit like accepting the evidence if it agrees with your preconceived notions and reject the evidence if it doesn’t.

Is cannabis on the whole better than some other substances? Sure. Does that make it harmless and invalidate this paper? No.

By evidence you mean the correlation? Yeah you're right, also we should all become pirates to fight climate change, since there's an (inverse) correlation between amount of pirates and temperature