Cannabis smoking associated with persistent epigenome-wide disruptions
bmcpulmmed.biomedcentral.com
bmcpulmmed.biomedcentral.com
They also report that the cannabis smoking group had a statistically significant difference in cigarette smoking, so that's probably a big confounder, along with other lifestyle choices that you might expect between people who report never smoking weed vs those who do.
It's just really really hard to make strong conclusions from a single study like this.
A related issue is pervasive discounting of personal safety with a pattern of unsafe strategies like taking drugs of unknown quality and unknown strength, and smoking burning substances without filtration under the "it's natural" fallacy.
Delta 9 is much different physiologically and psychologically and can induce this abhorrent behaviors.
Also in the mid to early 2000's over 50.3% of US adults (Pew Research Center) had tried cannabis, I can assure you someone in your "circle" has smoked in their life.
I don't think thats necessarily a quality of the drug itself. Most weed smokers of my generation were heavily saturated in a narrative that all drugs are bad and weed is horrifically addictive and on the same level as heroin. Someone who then smokes weed and realizes it was a lie would very plausibly start to doubt the danger and risk factor of harder drugs.
As with a lot of things, a bit of transparency and honesty goes a long way when it comes to harm reduction.