Generally I expect some basic scientific literacy on HN. But of course I should have learned by now to expect science denialism when ego is at stake.
If you want a concrete source look at any of the studies that cite the twin studies, including the meta-analysis from this year.
https://www.cambridge.org/core/journals/psychological-medici...
Scientific American is not a peer reviewed publication. They are science journalism and they aren't even particularly careful about their analysis. They posted an article in 2017 claiming cannabis might make you smarter:
https://www.scientificamerican.com/article/marijuana-may-boo...