"Frequent use of cannabis, especially the start of use at a younger age, doubles the risk of schizophrenia development in the future [
16]. Daily use of marijuana increases the risk of psychotic illness development with as much as five times higher risk in person using high potency THC"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442038/#:~:text=Frequent use of cannabis, especially,high potency THC [18].
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5042048/
Conclusions: Findings support the view that cannabis use may act to decrease educational achievement in young people. It is likely that this reflects the effects of the social context within which cannabis is used rather than any direct effect of cannabis on cognitive ability or motivation.
https://pubmed.ncbi.nlm.nih.gov/14651500/#:~:text=Conclusions: Findings support the view,on cognitive ability or motivation.
Yep, nowhere near as damaging
I can't see that either of those papers support the case for raising the classification of cannabis to the same level as heroin or cocaine. The first article, even disregarding it being poorly written and published in a questionable journal, comes to the conclusion that
...cannabis use, primarily THC in cannabis, in genetically predisposed or at-risk populations, leads to earlier diagnosis of psychosis/schizophrenia. This tells us that THC in cannabis has a small causative effect on schizophrenia...
...there is still more harm from cannabis than benefits, and adolescent cannabis usage should be discouraged at all costs. We still need more extensive studies for more detailed data about cannabis and its effects...
While the passage you quoted from the second seems to suggest that cannabis itself is less of a problem than the social context and environment in which it is taken. The paper also uses the term 'association' which does not imply causation. It also links heavy cannabis use with heavy smoking, risky drinking, and makes no comment regarding moderate cannabis use in adults beyond 'late adolescence'.
Taken together they would suggest to me, no expert on drug classification, that in terms of harm, cannabis is closer to alcohol than it is to heroin. The take home message, if there even is one, seems to be don't let kids and adolescents smoke a lot of weed. Same as booze, really.
That first article was really not well written though.