When people discuss cannabis, they usually also talk about its potential to cause psychosis. I have never heard the same about tobacco.
Recently, I stumbled across an interesting study. It suggests that tobacco and weed may be equally strongly associated with psychotic-like-experiences. I haven’t read the whole study, but via a quick google search I could find broadly the same result elsewhere: For example, there is a meta analysis in the Lancet Psychiatry that found
an overall relative risk of new psychotic disorders in daily smokers versus non-smokers of 2.18 (95% CI 1.23–3.85). Daily smokers developed psychotic illness at an earlier age than did non-smokers (weighted mean difference −1.04 years, 95% CI −1.82 to −0.26). Those with psychosis started smoking at a non-significantly earlier age than did healthy controls (−0.44 years, 95% CI −1.21 to 0.34).
There is also a popular science article that reports about it (and also about adverse effects from cannabis).
The obvious concern is of course this: Does smoking/cannabis cause psychosis or are people who are more prone to be smokers simply more prone to developing psychosis? Another study address that and looks at the role of nicotine. Trying to do them justice I would say they at least believe that some kind of causal relationship could be plausible.
Why is this not a much bigger thing? I am confused.