That is an article from 1981. A *lot* of research has been done since then, which has confirmed and added details about how marijuana causes damage at the cellular and molecular level. And more research is still needed.
There was pretty much a research desert until this big experiment with quasi-legal marijuana began a few years ago. Now, a lot of researchers are interested in the subject, since the potential threat to public health is so high.
I've posted more evidence than you have. Whether that concerns you is of course up to you.